The linked commit reverts the change that accidentally used some sysfs enable/disable functions from Perf which broke the refcounting, but it also removes the fact that the sysfs disable function disabled the helpers.

Add a new wrapper function that does both which is used by both Perf and sysfs, and label the sysfs disable function appropriately. The naming of all of the functions will be tidied up later to avoid this happening again.

Fixes: 287e82cf69aa ("coresight: Fix crash when Perf and sysfs modes are used concurrently") Signed-off-by: James Clark james.clark@arm.com --- drivers/hwtracing/coresight/coresight-core.c | 30 ++++++++++++++----- .../hwtracing/coresight/coresight-etm-perf.c | 2 +- drivers/hwtracing/coresight/coresight-priv.h | 2 +- 3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index d7f0e231feb9..965bb6d4e1bf 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -441,8 +441,26 @@ static void coresight_disable_helpers(struct coresight_device *csdev) } }

+/* + * Helper function to call source_ops(csdev)->disable and also disable the + * helpers. + * + * There is an imbalance between coresight_enable_path() and + * coresight_disable_path(). Enabling also enables the source's helpers as part + * of the path, but disabling always skips the first item in the path (which is + * the source), so sources and their helpers don't get disabled as part of that + * function and we need the extra step here. + */ +void coresight_disable_source(struct coresight_device *csdev, void *data) +{ + if (source_ops(csdev)->disable) + source_ops(csdev)->disable(csdev, data); + coresight_disable_helpers(csdev); +} +EXPORT_SYMBOL_GPL(coresight_disable_source); + /** - * coresight_disable_source - Drop the reference count by 1 and disable + * coresight_disable_source_sysfs - Drop the reference count by 1 and disable * the device if there are no users left. * * @csdev: The coresight device to disable @@ -451,17 +469,15 @@ static void coresight_disable_helpers(struct coresight_device *csdev) * * Returns true if the device has been disabled. */ -bool coresight_disable_source(struct coresight_device *csdev, void *data) +static bool coresight_disable_source_sysfs(struct coresight_device *csdev, + void *data) { if (atomic_dec_return(&csdev->refcnt) == 0) { - if (source_ops(csdev)->disable) - source_ops(csdev)->disable(csdev, data); - coresight_disable_helpers(csdev); + coresight_disable_source(csdev, data); csdev->enable = false; } return !csdev->enable; } -EXPORT_SYMBOL_GPL(coresight_disable_source);

/* * coresight_disable_path_from : Disable components in the given path beyond @@ -1204,7 +1220,7 @@ void coresight_disable(struct coresight_device *csdev) if (ret) goto out;

- if (!csdev->enable || !coresight_disable_source(csdev, NULL)) + if (!csdev->enable || !coresight_disable_source_sysfs(csdev, NULL)) goto out;

switch (csdev->subtype.source_subtype) { diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c index a52cfcce25d6..c0c60e6a1703 100644 --- a/drivers/hwtracing/coresight/coresight-etm-perf.c +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c @@ -589,7 +589,7 @@ static void etm_event_stop(struct perf_event *event, int mode) return;

/* stop tracer */ - source_ops(csdev)->disable(csdev, event); + coresight_disable_source(csdev, event);

/* tell the core */ event->hw.state = PERF_HES_STOPPED; diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h index 767076e07970..30c051055e54 100644 --- a/drivers/hwtracing/coresight/coresight-priv.h +++ b/drivers/hwtracing/coresight/coresight-priv.h @@ -233,6 +233,6 @@ void coresight_set_percpu_sink(int cpu, struct coresight_device *csdev); struct coresight_device *coresight_get_percpu_sink(int cpu); int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode, void *data); -bool coresight_disable_source(struct coresight_device *csdev, void *data); +void coresight_disable_source(struct coresight_device *csdev, void *data);

#endif

The check for the existence of callbacks before using them implies that this happens and is supported. There are no devices without enable/disable callbacks, and it wouldn't be possible to add a new working device without adding them either, so just remove them.

Furthermore, there are more callbacks than just enable and disable that are already used unguarded in other places.

The comment about new session compatibility doesn't seem to match up to the line of code that it's on so remove it. I think it's alluding to the fact that sinks will check if they were already enabled via sysfs or Perf and fail the enable. But there are more detailed comments at those places, and this one isn't very useful.

Signed-off-by: James Clark james.clark@arm.com --- drivers/hwtracing/coresight/coresight-core.c | 51 +++++--------------- 1 file changed, 12 insertions(+), 39 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index f79aa9ff9b64..ab226441e5f4 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -279,16 +279,8 @@ EXPORT_SYMBOL_GPL(coresight_add_helper); static int coresight_enable_sink(struct coresight_device *csdev, enum cs_mode mode, void *data) { - int ret; - - /* - * We need to make sure the "new" session is compatible with the - * existing "mode" of operation. - */ - if (!sink_ops(csdev)->enable) - return -EINVAL; + int ret = sink_ops(csdev)->enable(csdev, mode, data);

- ret = sink_ops(csdev)->enable(csdev, mode, data); if (ret) return ret;

@@ -299,12 +291,7 @@ static int coresight_enable_sink(struct coresight_device *csdev,

static void coresight_disable_sink(struct coresight_device *csdev) { - int ret; - - if (!sink_ops(csdev)->disable) - return; - - ret = sink_ops(csdev)->disable(csdev); + int ret = sink_ops(csdev)->disable(csdev); if (ret) return; csdev->enable = false; @@ -330,11 +317,9 @@ static int coresight_enable_link(struct coresight_device *csdev, if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT && IS_ERR(outconn)) return PTR_ERR(outconn);

- if (link_ops(csdev)->enable) { - ret = link_ops(csdev)->enable(csdev, inconn, outconn); - if (!ret) - csdev->enable = true; - } + ret = link_ops(csdev)->enable(csdev, inconn, outconn); + if (!ret) + csdev->enable = true;

return ret; } @@ -354,9 +339,7 @@ static void coresight_disable_link(struct coresight_device *csdev, outconn = coresight_find_out_connection(csdev, child); link_subtype = csdev->subtype.link_subtype;

- if (link_ops(csdev)->disable) { - link_ops(csdev)->disable(csdev, inconn, outconn); - } + link_ops(csdev)->disable(csdev, inconn, outconn);

if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG) { for (i = 0; i < csdev->pdata->nr_inconns; i++) @@ -382,11 +365,9 @@ int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode, int ret;

if (!csdev->enable) { - if (source_ops(csdev)->enable) { - ret = source_ops(csdev)->enable(csdev, data, mode); - if (ret) - return ret; - } + ret = source_ops(csdev)->enable(csdev, data, mode); + if (ret) + return ret; csdev->enable = true; }

@@ -404,11 +385,8 @@ static bool coresight_is_helper(struct coresight_device *csdev) static int coresight_enable_helper(struct coresight_device *csdev, enum cs_mode mode, void *data) { - int ret; + int ret = helper_ops(csdev)->enable(csdev, mode, data);

- if (!helper_ops(csdev)->enable) - return 0; - ret = helper_ops(csdev)->enable(csdev, mode, data); if (ret) return ret;

@@ -418,12 +396,8 @@ static int coresight_enable_helper(struct coresight_device *csdev,

static void coresight_disable_helper(struct coresight_device *csdev) { - int ret; - - if (!helper_ops(csdev)->disable) - return; + int ret = helper_ops(csdev)->disable(csdev, NULL);

- ret = helper_ops(csdev)->disable(csdev, NULL); if (ret) return; csdev->enable = false; @@ -453,8 +427,7 @@ static void coresight_disable_helpers(struct coresight_device *csdev) */ void coresight_disable_source(struct coresight_device *csdev, void *data) { - if (source_ops(csdev)->disable) - source_ops(csdev)->disable(csdev, data); + source_ops(csdev)->disable(csdev, data); coresight_disable_helpers(csdev); } EXPORT_SYMBOL_GPL(coresight_disable_source);

'enable', which probably should have been 'enabled', is only ever read in the core code in relation to controlling sources, and specifically only sources in sysfs mode. Confusingly it's not labelled as such and relying on it can be a source of bugs like the one fixed by commit 078dbba3f0c9 ("coresight: Fix crash when Perf and sysfs modes are used concurrently").

Most importantly, it can only be used when the coresight_mutex is held which is only done when enabling and disabling paths in sysfs mode, and not Perf mode. So to prevent its usage spreading and leaking out to other devices, remove it.

It's use is equivalent to checking if the mode is currently sysfs, as due to the coresight_mutex lock, mode == CS_MODE_SYSFS can only become true or untrue when that lock is held, and when mode == CS_MODE_SYSFS the device is both enabled and in sysfs mode.

The one place it was used outside of the core code is in TPDA, but that pattern is more appropriately represented using refcounts inside the device's own spinlock.

Signed-off-by: James Clark james.clark@arm.com --- drivers/hwtracing/coresight/coresight-core.c | 86 +++++++------------- drivers/hwtracing/coresight/coresight-tpda.c | 12 ++- include/linux/coresight.h | 2 - 3 files changed, 38 insertions(+), 62 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index ab226441e5f4..1d0bd1586590 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -279,29 +279,18 @@ EXPORT_SYMBOL_GPL(coresight_add_helper); static int coresight_enable_sink(struct coresight_device *csdev, enum cs_mode mode, void *data) { - int ret = sink_ops(csdev)->enable(csdev, mode, data); - - if (ret) - return ret; - - csdev->enable = true; - - return 0; + return sink_ops(csdev)->enable(csdev, mode, data); }

static void coresight_disable_sink(struct coresight_device *csdev) { - int ret = sink_ops(csdev)->disable(csdev); - if (ret) - return; - csdev->enable = false; + sink_ops(csdev)->disable(csdev); }

static int coresight_enable_link(struct coresight_device *csdev, struct coresight_device *parent, struct coresight_device *child) { - int ret = 0; int link_subtype; struct coresight_connection *inconn, *outconn;

@@ -317,19 +306,13 @@ static int coresight_enable_link(struct coresight_device *csdev, if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT && IS_ERR(outconn)) return PTR_ERR(outconn);

- ret = link_ops(csdev)->enable(csdev, inconn, outconn); - if (!ret) - csdev->enable = true; - - return ret; + return link_ops(csdev)->enable(csdev, inconn, outconn); }

static void coresight_disable_link(struct coresight_device *csdev, struct coresight_device *parent, struct coresight_device *child) { - int i; - int link_subtype; struct coresight_connection *inconn, *outconn;

if (!parent || !child) @@ -337,26 +320,8 @@ static void coresight_disable_link(struct coresight_device *csdev,

inconn = coresight_find_out_connection(parent, csdev); outconn = coresight_find_out_connection(csdev, child); - link_subtype = csdev->subtype.link_subtype;

link_ops(csdev)->disable(csdev, inconn, outconn); - - if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG) { - for (i = 0; i < csdev->pdata->nr_inconns; i++) - if (atomic_read(&csdev->pdata->in_conns[i]->dest_refcnt) != - 0) - return; - } else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT) { - for (i = 0; i < csdev->pdata->nr_outconns; i++) - if (atomic_read(&csdev->pdata->out_conns[i]->src_refcnt) != - 0) - return; - } else { - if (atomic_read(&csdev->refcnt) != 0) - return; - } - - csdev->enable = false; }

int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode, @@ -364,11 +329,16 @@ int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode, { int ret;

- if (!csdev->enable) { + /* + * Comparison with CS_MODE_SYSFS works without taking any device + * specific spinlock because the truthyness of that comparison can only + * change with coresight_mutex held, which we already have here. + */ + lockdep_assert_held(&coresight_mutex); + if (local_read(&csdev->mode) != CS_MODE_SYSFS) { ret = source_ops(csdev)->enable(csdev, data, mode); if (ret) return ret; - csdev->enable = true; }

atomic_inc(&csdev->refcnt); @@ -385,22 +355,12 @@ static bool coresight_is_helper(struct coresight_device *csdev) static int coresight_enable_helper(struct coresight_device *csdev, enum cs_mode mode, void *data) { - int ret = helper_ops(csdev)->enable(csdev, mode, data); - - if (ret) - return ret; - - csdev->enable = true; - return 0; + return helper_ops(csdev)->enable(csdev, mode, data); }

static void coresight_disable_helper(struct coresight_device *csdev) { - int ret = helper_ops(csdev)->disable(csdev, NULL); - - if (ret) - return; - csdev->enable = false; + helper_ops(csdev)->disable(csdev, NULL); }

static void coresight_disable_helpers(struct coresight_device *csdev) @@ -445,11 +405,15 @@ EXPORT_SYMBOL_GPL(coresight_disable_source); static bool coresight_disable_source_sysfs(struct coresight_device *csdev, void *data) { + lockdep_assert_held(&coresight_mutex); + if (local_read(&csdev->mode) != CS_MODE_SYSFS) + return false; + if (atomic_dec_return(&csdev->refcnt) == 0) { coresight_disable_source(csdev, data); - csdev->enable = false; + return true; } - return !csdev->enable; + return false; }

/* @@ -1097,7 +1061,13 @@ int coresight_enable(struct coresight_device *csdev) if (ret) goto out;

- if (csdev->enable) { + /* + * mode == SYSFS implies that it's already enabled. Don't look at the + * refcount to determine this because we don't claim the source until + * coresight_enable_source() so can still race with Perf mode which + * doesn't hold coresight_mutex. + */ + if (local_read(&csdev->mode) == CS_MODE_SYSFS) { /* * There could be multiple applications driving the software * source. So keep the refcount for each such user when the @@ -1183,7 +1153,7 @@ void coresight_disable(struct coresight_device *csdev) if (ret) goto out;

- if (!csdev->enable || !coresight_disable_source_sysfs(csdev, NULL)) + if (!coresight_disable_source_sysfs(csdev, NULL)) goto out;

switch (csdev->subtype.source_subtype) { @@ -1249,7 +1219,9 @@ static ssize_t enable_source_show(struct device *dev, { struct coresight_device *csdev = to_coresight_device(dev);

- return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->enable); + guard(mutex)(&coresight_mutex); + return scnprintf(buf, PAGE_SIZE, "%u\n", + local_read(&csdev->mode) == CS_MODE_SYSFS); }

static ssize_t enable_source_store(struct device *dev, diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c index 5f82737c37bb..65c70995ab00 100644 --- a/drivers/hwtracing/coresight/coresight-tpda.c +++ b/drivers/hwtracing/coresight/coresight-tpda.c @@ -148,7 +148,11 @@ static int __tpda_enable(struct tpda_drvdata *drvdata, int port)

CS_UNLOCK(drvdata->base);

- if (!drvdata->csdev->enable) + /* + * Only do pre-port enable for first port that calls enable when the + * device's main refcount is still 0 + */ + if (!atomic_read(&drvdata->csdev->refcnt)) tpda_enable_pre_port(drvdata);

ret = tpda_enable_port(drvdata, port); @@ -169,6 +173,7 @@ static int tpda_enable(struct coresight_device *csdev, ret = __tpda_enable(drvdata, in->dest_port); if (!ret) { atomic_inc(&in->dest_refcnt); + atomic_inc(&csdev->refcnt); dev_dbg(drvdata->dev, "TPDA inport %d enabled.\n", in->dest_port); } } @@ -197,9 +202,10 @@ static void tpda_disable(struct coresight_device *csdev, struct tpda_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

spin_lock(&drvdata->spinlock); - if (atomic_dec_return(&in->dest_refcnt) == 0) + if (atomic_dec_return(&in->dest_refcnt) == 0) { __tpda_disable(drvdata, in->dest_port); - + atomic_dec(&csdev->refcnt); + } spin_unlock(&drvdata->spinlock);

dev_dbg(drvdata->dev, "TPDA inport %d disabled\n", in->dest_port); diff --git a/include/linux/coresight.h b/include/linux/coresight.h index ba817f563ff7..46e6667f72ce 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -233,7 +233,6 @@ struct coresight_sysfs_link { * a non-atomic read would also work. * @refcnt: keep track of what is in use. * @orphan: true if the component has connections that haven't been linked. - * @enable: 'true' if component is currently part of an active path. * @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs * by writing a 1 to the 'enable_sink' file. A sink can be * activated but not yet enabled. Enabling for a _sink_ happens @@ -260,7 +259,6 @@ struct coresight_device { local_t mode; atomic_t refcnt; bool orphan; - bool enable; /* sink specific fields */ bool sysfs_sink_activated; struct dev_ext_attribute *ea;

Refcnt is only ever accessed from either inside the coresight_mutex, or the device's spinlock, making the atomic type and atomic_dec_return() calls confusing and unnecessary. The only point of synchronisation outside of these two types of locks is already done with a compare and swap on 'mode', which a comment has been added for.

There was one instance of refcnt being used outside of a lock in TPIU, but that can easily be fixed by making it the same as all the other devices and adding a spinlock. Potentially in the future all the refcounting and locking can be moved up into the core code, and all the mostly duplicate code from the individual devices can be removed.

Signed-off-by: James Clark james.clark@arm.com --- drivers/hwtracing/coresight/coresight-etb10.c | 11 +++++----- drivers/hwtracing/coresight/coresight-sysfs.c | 7 ++++--- .../hwtracing/coresight/coresight-tmc-etf.c | 20 ++++++++++--------- .../hwtracing/coresight/coresight-tmc-etr.c | 13 ++++++------ drivers/hwtracing/coresight/coresight-tpda.c | 7 ++++--- drivers/hwtracing/coresight/coresight-tpiu.c | 14 +++++++++++-- drivers/hwtracing/coresight/ultrasoc-smb.c | 9 +++++---- include/linux/coresight.h | 13 +++++++++--- 8 files changed, 59 insertions(+), 35 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index 08e5bba862db..5f2bb95955b7 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -161,7 +161,7 @@ static int etb_enable_sysfs(struct coresight_device *csdev) local_set(&csdev->mode, CS_MODE_SYSFS); }

- atomic_inc(&csdev->refcnt); + csdev->refcnt++; out: spin_unlock_irqrestore(&drvdata->spinlock, flags); return ret; @@ -197,7 +197,7 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data) * use for this session. */ if (drvdata->pid == pid) { - atomic_inc(&csdev->refcnt); + csdev->refcnt++; goto out; }

@@ -215,7 +215,7 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data) /* Associate with monitored process. */ drvdata->pid = pid; local_set(&drvdata->csdev->mode, CS_MODE_PERF); - atomic_inc(&csdev->refcnt); + csdev->refcnt++; }

out: @@ -354,7 +354,8 @@ static int etb_disable(struct coresight_device *csdev)

spin_lock_irqsave(&drvdata->spinlock, flags);

- if (atomic_dec_return(&csdev->refcnt)) { + csdev->refcnt--; + if (csdev->refcnt) { spin_unlock_irqrestore(&drvdata->spinlock, flags); return -EBUSY; } @@ -445,7 +446,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev, spin_lock_irqsave(&drvdata->spinlock, flags);

/* Don't do anything if another tracer is using this sink */ - if (atomic_read(&csdev->refcnt) != 1) + if (csdev->refcnt != 1) goto out;

__etb_disable_hw(drvdata); diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c index 92cdf8139f23..5992f2c2200a 100644 --- a/drivers/hwtracing/coresight/coresight-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-sysfs.c @@ -68,7 +68,7 @@ static int coresight_enable_source_sysfs(struct coresight_device *csdev, return ret; }

- atomic_inc(&csdev->refcnt); + csdev->refcnt++;

return 0; } @@ -90,7 +90,8 @@ static bool coresight_disable_source_sysfs(struct coresight_device *csdev, if (local_read(&csdev->mode) != CS_MODE_SYSFS) return false;

- if (atomic_dec_return(&csdev->refcnt) == 0) { + csdev->refcnt--; + if (csdev->refcnt == 0) { coresight_disable_source(csdev, data); return true; } @@ -190,7 +191,7 @@ int coresight_enable_sysfs(struct coresight_device *csdev) * source is already enabled. */ if (subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE) - atomic_inc(&csdev->refcnt); + csdev->refcnt++; goto out; }

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index 2a7e516052a2..f3281c958a57 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -206,7 +206,7 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev) * touched. */ if (local_read(&csdev->mode) == CS_MODE_SYSFS) { - atomic_inc(&csdev->refcnt); + csdev->refcnt++; goto out; }

@@ -229,7 +229,7 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev) ret = tmc_etb_enable_hw(drvdata); if (!ret) { local_set(&csdev->mode, CS_MODE_SYSFS); - atomic_inc(&csdev->refcnt); + csdev->refcnt++; } else { /* Free up the buffer if we failed to enable */ used = false; @@ -284,7 +284,7 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data) * use for this session. */ if (drvdata->pid == pid) { - atomic_inc(&csdev->refcnt); + csdev->refcnt++; break; }

@@ -293,7 +293,7 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data) /* Associate with monitored process. */ drvdata->pid = pid; local_set(&csdev->mode, CS_MODE_PERF); - atomic_inc(&csdev->refcnt); + csdev->refcnt++; } } while (0); spin_unlock_irqrestore(&drvdata->spinlock, flags); @@ -338,7 +338,8 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev) return -EBUSY; }

- if (atomic_dec_return(&csdev->refcnt)) { + csdev->refcnt--; + if (csdev->refcnt) { spin_unlock_irqrestore(&drvdata->spinlock, flags); return -EBUSY; } @@ -371,7 +372,7 @@ static int tmc_enable_etf_link(struct coresight_device *csdev, return -EBUSY; }

- if (atomic_read(&csdev->refcnt) == 0) { + if (csdev->refcnt == 0) { ret = tmc_etf_enable_hw(drvdata); if (!ret) { local_set(&csdev->mode, CS_MODE_SYSFS); @@ -379,7 +380,7 @@ static int tmc_enable_etf_link(struct coresight_device *csdev, } } if (!ret) - atomic_inc(&csdev->refcnt); + csdev->refcnt++; spin_unlock_irqrestore(&drvdata->spinlock, flags);

if (first_enable) @@ -401,7 +402,8 @@ static void tmc_disable_etf_link(struct coresight_device *csdev, return; }

- if (atomic_dec_return(&csdev->refcnt) == 0) { + csdev->refcnt--; + if (csdev->refcnt == 0) { tmc_etf_disable_hw(drvdata); local_set(&csdev->mode, CS_MODE_DISABLED); last_disable = true; @@ -489,7 +491,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev, spin_lock_irqsave(&drvdata->spinlock, flags);

/* Don't do anything if another tracer is using this sink */ - if (atomic_read(&csdev->refcnt) != 1) + if (csdev->refcnt != 1) goto out;

CS_UNLOCK(drvdata->base); diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 3dc989d4fcab..88a0fc375b4d 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -1231,14 +1231,14 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev) * touched, even if the buffer size has changed. */ if (local_read(&csdev->mode) == CS_MODE_SYSFS) { - atomic_inc(&csdev->refcnt); + csdev->refcnt++; goto out; }

ret = tmc_etr_enable_hw(drvdata, sysfs_buf); if (!ret) { local_set(&csdev->mode, CS_MODE_SYSFS); - atomic_inc(&csdev->refcnt); + csdev->refcnt++; }

out: @@ -1564,7 +1564,7 @@ tmc_update_etr_buffer(struct coresight_device *csdev, spin_lock_irqsave(&drvdata->spinlock, flags);

/* Don't do anything if another tracer is using this sink */ - if (atomic_read(&csdev->refcnt) != 1) { + if (csdev->refcnt != 1) { spin_unlock_irqrestore(&drvdata->spinlock, flags); goto out; } @@ -1676,7 +1676,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data) * use for this session. */ if (drvdata->pid == pid) { - atomic_inc(&csdev->refcnt); + csdev->refcnt++; goto unlock_out; }

@@ -1686,7 +1686,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data) drvdata->pid = pid; local_set(&csdev->mode, CS_MODE_PERF); drvdata->perf_buf = etr_perf->etr_buf; - atomic_inc(&csdev->refcnt); + csdev->refcnt++; }

unlock_out: @@ -1719,7 +1719,8 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev) return -EBUSY; }

- if (atomic_dec_return(&csdev->refcnt)) { + csdev->refcnt--; + if (csdev->refcnt) { spin_unlock_irqrestore(&drvdata->spinlock, flags); return -EBUSY; } diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c index 65c70995ab00..135a89654c4c 100644 --- a/drivers/hwtracing/coresight/coresight-tpda.c +++ b/drivers/hwtracing/coresight/coresight-tpda.c @@ -152,7 +152,8 @@ static int __tpda_enable(struct tpda_drvdata *drvdata, int port) * Only do pre-port enable for first port that calls enable when the * device's main refcount is still 0 */ - if (!atomic_read(&drvdata->csdev->refcnt)) + lockdep_assert_held(&drvdata->spinlock); + if (!drvdata->csdev->refcnt) tpda_enable_pre_port(drvdata);

ret = tpda_enable_port(drvdata, port); @@ -173,7 +174,7 @@ static int tpda_enable(struct coresight_device *csdev, ret = __tpda_enable(drvdata, in->dest_port); if (!ret) { atomic_inc(&in->dest_refcnt); - atomic_inc(&csdev->refcnt); + csdev->refcnt++; dev_dbg(drvdata->dev, "TPDA inport %d enabled.\n", in->dest_port); } } @@ -204,7 +205,7 @@ static void tpda_disable(struct coresight_device *csdev, spin_lock(&drvdata->spinlock); if (atomic_dec_return(&in->dest_refcnt) == 0) { __tpda_disable(drvdata, in->dest_port); - atomic_dec(&csdev->refcnt); + csdev->refcnt--; } spin_unlock(&drvdata->spinlock);

diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c b/drivers/hwtracing/coresight/coresight-tpiu.c index 59eac93fd6bb..c23a6b9b41fe 100644 --- a/drivers/hwtracing/coresight/coresight-tpiu.c +++ b/drivers/hwtracing/coresight/coresight-tpiu.c @@ -58,6 +58,7 @@ struct tpiu_drvdata { void __iomem *base; struct clk *atclk; struct coresight_device *csdev; + spinlock_t spinlock; };

static void tpiu_enable_hw(struct csdev_access *csa) @@ -72,8 +73,11 @@ static void tpiu_enable_hw(struct csdev_access *csa) static int tpiu_enable(struct coresight_device *csdev, enum cs_mode mode, void *__unused) { + struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); + + guard(spinlock)(&drvdata->spinlock); tpiu_enable_hw(&csdev->access); - atomic_inc(&csdev->refcnt); + csdev->refcnt++; dev_dbg(&csdev->dev, "TPIU enabled\n"); return 0; } @@ -96,7 +100,11 @@ static void tpiu_disable_hw(struct csdev_access *csa)

static int tpiu_disable(struct coresight_device *csdev) { - if (atomic_dec_return(&csdev->refcnt)) + struct tpiu_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent); + + guard(spinlock)(&drvdata->spinlock); + csdev->refcnt--; + if (csdev->refcnt) return -EBUSY;

tpiu_disable_hw(&csdev->access); @@ -132,6 +140,8 @@ static int tpiu_probe(struct amba_device *adev, const struct amba_id *id) if (!drvdata) return -ENOMEM;

+ spin_lock_init(&drvdata->spinlock); + drvdata->atclk = devm_clk_get(&adev->dev, "atclk"); /* optional */ if (!IS_ERR(drvdata->atclk)) { ret = clk_prepare_enable(drvdata->atclk); diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c index 1a8c64645b92..1146584a1745 100644 --- a/drivers/hwtracing/coresight/ultrasoc-smb.c +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c @@ -103,7 +103,7 @@ static int smb_open(struct inode *inode, struct file *file) if (drvdata->reading) return -EBUSY;

- if (atomic_read(&drvdata->csdev->refcnt)) + if (drvdata->csdev->refcnt) return -EBUSY;

smb_update_data_size(drvdata); @@ -271,7 +271,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode, if (ret) return ret;

- atomic_inc(&csdev->refcnt); + csdev->refcnt++; dev_dbg(&csdev->dev, "Ultrasoc SMB enabled\n");

return ret; @@ -286,7 +286,8 @@ static int smb_disable(struct coresight_device *csdev) if (drvdata->reading) return -EBUSY;

- if (atomic_dec_return(&csdev->refcnt)) + csdev->refcnt--; + if (csdev->refcnt) return -EBUSY;

/* Complain if we (somehow) got out of sync */ @@ -381,7 +382,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev, guard(spinlock)(&drvdata->spinlock);

/* Don't do anything if another tracer is using this sink. */ - if (atomic_read(&csdev->refcnt) != 1) + if (csdev->refcnt != 1) return 0;

smb_disable_hw(drvdata); diff --git a/include/linux/coresight.h b/include/linux/coresight.h index e8dd0df98881..4400d554a16b 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -230,8 +230,15 @@ struct coresight_sysfs_link { * actually an 'enum cs_mode', but is stored in an atomic type. * This is always accessed through local_read() and local_set(), * but wherever it's done from within the Coresight device's lock, - * a non-atomic read would also work. - * @refcnt: keep track of what is in use. + * a non-atomic read would also work. This is the main point of + * synchronisation between code happening inside the sysfs mode's + * coresight_mutex and outside when running in Perf mode. A compare + * and exchange swap is done to atomically claim one mode or the + * other. + * @refcnt: keep track of what is in use. Only access this outside of the + * device's spinlock when the coresight_mutex held and mode == + * CS_MODE_SYSFS. Otherwise it must be accessed from inside the + * spinlock. * @orphan: true if the component has connections that haven't been linked. * @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs * by writing a 1 to the 'enable_sink' file. A sink can be @@ -257,7 +264,7 @@ struct coresight_device { struct csdev_access access; struct device dev; local_t mode; - atomic_t refcnt; + int refcnt; bool orphan; /* sink specific fields */ bool sysfs_sink_activated;

Hi James

On 12/12/2023 15:53, James Clark wrote:

The linked commit reverts the change that accidentally used some sysfs enable/disable functions from Perf which broke the refcounting, but it also removes the fact that the sysfs disable function disabled the helpers.

Add a new wrapper function that does both which is used by both Perf and sysfs, and label the sysfs disable function appropriately. The naming of all of the functions will be tidied up later to avoid this happening again.

Fixes: 287e82cf69aa ("coresight: Fix crash when Perf and sysfs modes are used concurrently")

But we still don't "enable" the helpers from perf mode with this patch. i.e., we use source_ops()->enable directly. So, I guess this patch doesn't fix a bug as such. But that said, it would be good to enable/disable helpers for sources, in perf mode.

Suzuki

Signed-off-by: James Clark james.clark@arm.com

drivers/hwtracing/coresight/coresight-core.c | 30 ++++++++++++++----- .../hwtracing/coresight/coresight-etm-perf.c | 2 +- drivers/hwtracing/coresight/coresight-priv.h | 2 +- 3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index d7f0e231feb9..965bb6d4e1bf 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -441,8 +441,26 @@ static void coresight_disable_helpers(struct coresight_device *csdev) } } +/*

• • Helper function to call source_ops(csdev)->disable and also disable the
• • helpers.
• • There is an imbalance between coresight_enable_path() and
• • coresight_disable_path(). Enabling also enables the source's helpers as part
• • of the path, but disabling always skips the first item in the path (which is
• • the source), so sources and their helpers don't get disabled as part of that
• • function and we need the extra step here.
• */

+void coresight_disable_source(struct coresight_device *csdev, void *data) +{

• if (source_ops(csdev)->disable)

• source_ops(csdev)->disable(csdev, data);
  

• coresight_disable_helpers(csdev);

+} +EXPORT_SYMBOL_GPL(coresight_disable_source);

• /**

• • coresight_disable_source - Drop the reference count by 1 and disable

• • coresight_disable_source_sysfs - Drop the reference count by 1 and disable
  • the device if there are no users left.
  • @csdev: The coresight device to disable

@@ -451,17 +469,15 @@ static void coresight_disable_helpers(struct coresight_device *csdev)

• Returns true if the device has been disabled.

*/ -bool coresight_disable_source(struct coresight_device *csdev, void *data) +static bool coresight_disable_source_sysfs(struct coresight_device *csdev,

• 			   void *data)
  

  { if (atomic_dec_return(&csdev->refcnt) == 0) {

• if (source_ops(csdev)->disable)
  

• 	source_ops(csdev)->disable(csdev, data);
  

• coresight_disable_helpers(csdev);
  

• coresight_disable_source(csdev, data);
  

  csdev->enable = false; } return !csdev->enable; }

-EXPORT_SYMBOL_GPL(coresight_disable_source); /*

• coresight_disable_path_from : Disable components in the given path beyond

@@ -1204,7 +1220,7 @@ void coresight_disable(struct coresight_device *csdev) if (ret) goto out;

• if (!csdev->enable || !coresight_disable_source(csdev, NULL))

• if (!csdev->enable || !coresight_disable_source_sysfs(csdev, NULL)) goto out;

switch (csdev->subtype.source_subtype) { diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c index a52cfcce25d6..c0c60e6a1703 100644 --- a/drivers/hwtracing/coresight/coresight-etm-perf.c +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c @@ -589,7 +589,7 @@ static void etm_event_stop(struct perf_event *event, int mode) return; /* stop tracer */

• source_ops(csdev)->disable(csdev, event);

• coresight_disable_source(csdev, event);

Does this result i

/* tell the core */ event->hw.state = PERF_HES_STOPPED; diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h index 767076e07970..30c051055e54 100644 --- a/drivers/hwtracing/coresight/coresight-priv.h +++ b/drivers/hwtracing/coresight/coresight-priv.h @@ -233,6 +233,6 @@ void coresight_set_percpu_sink(int cpu, struct coresight_device *csdev); struct coresight_device *coresight_get_percpu_sink(int cpu); int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode, void *data); -bool coresight_disable_source(struct coresight_device *csdev, void *data); +void coresight_disable_source(struct coresight_device *csdev, void *data); #endif

On 12/12/2023 15:54, James Clark wrote:

Most devices use mode, so move the mode definition out of the individual devices and up to the Coresight device. This will allow the core code to also know the mode which will be useful in a later commit.

This also fixes the inconsistency of the documentation of the mode field on the individual device types. For example ETB10 had "this ETB is being used".

Two devices didn't require an atomic mode type, so these usages have been converted to atomic_get() and atomic_set() only to make it compile, but the documentation of the field in struct coresight_device explains this type of usage.

In the future, manipulation of the mode could be completely moved out of the individual devices and into the core code because it's almost all duplicate code, and this change is a step towards that.

The change looks good to me. I am wondering if we should abstract it out ?

i.e., csdev_get_mode(struct coresight_device *csdev) csdev_set_mode(struct coresight_device *csdev, mode) csdev_{cmpxchg or set_if}_mode(csdev, old_mode, new_mode)

Signed-off-by: James Clark james.clark@arm.com

drivers/hwtracing/coresight/coresight-etb10.c | 18 ++++++------- drivers/hwtracing/coresight/coresight-etm.h | 2 -- .../coresight/coresight-etm3x-core.c | 13 +++++----- .../coresight/coresight-etm3x-sysfs.c | 4 +-- drivers/hwtracing/coresight/coresight-stm.c | 20 +++++++------- .../hwtracing/coresight/coresight-tmc-core.c | 2 +- .../hwtracing/coresight/coresight-tmc-etf.c | 26 +++++++++---------- .../hwtracing/coresight/coresight-tmc-etr.c | 20 +++++++------- drivers/hwtracing/coresight/coresight-tmc.h | 2 -- drivers/hwtracing/coresight/ultrasoc-smb.c | 13 +++++----- drivers/hwtracing/coresight/ultrasoc-smb.h | 2 -- include/linux/coresight.h | 6 +++++ 12 files changed, 62 insertions(+), 66 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index fa80039e0821..08e5bba862db 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -76,7 +76,6 @@ DEFINE_CORESIGHT_DEVLIST(etb_devs, "etb");

• @pid: Process ID of the process being monitored by the session

• that is using this component.
  

• @buf: area of memory where ETB buffer content gets sent.

• • @mode: this ETB is being used.
  • @buffer_depth: size of @buf.
  • @trigger_cntr: amount of words to store after a trigger.
  */

@@ -89,7 +88,6 @@ struct etb_drvdata { local_t reading; pid_t pid; u8 *buf;

• u32 mode; u32 buffer_depth; u32 trigger_cntr; };

@@ -150,17 +148,17 @@ static int etb_enable_sysfs(struct coresight_device *csdev) spin_lock_irqsave(&drvdata->spinlock, flags); /* Don't messup with perf sessions. */

• if (drvdata->mode == CS_MODE_PERF) {

• if (local_read(&csdev->mode) == CS_MODE_PERF) { ret = -EBUSY; goto out; }

• if (drvdata->mode == CS_MODE_DISABLED) {

• if (local_read(&csdev->mode) == CS_MODE_DISABLED) { ret = etb_enable_hw(drvdata); if (ret) goto out;

• drvdata->mode = CS_MODE_SYSFS;
  

• local_set(&csdev->mode, CS_MODE_SYSFS);
  

  }

atomic_inc(&csdev->refcnt); @@ -181,7 +179,7 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data) spin_lock_irqsave(&drvdata->spinlock, flags); /* No need to continue if the component is already in used by sysFS. */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) { ret = -EBUSY; goto out; }

@@ -216,7 +214,7 @@ static int etb_enable_perf(struct coresight_device *csdev, void *data) if (!ret) { /* Associate with monitored process. */ drvdata->pid = pid;

• drvdata->mode = CS_MODE_PERF;
  

• local_set(&drvdata->csdev->mode, CS_MODE_PERF);
  

  atomic_inc(&csdev->refcnt); }

@@ -362,11 +360,11 @@ static int etb_disable(struct coresight_device *csdev) } /* Complain if we (somehow) got out of sync */

• WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);

• WARN_ON_ONCE(local_read(&csdev->mode) == CS_MODE_DISABLED); etb_disable_hw(drvdata); /* Dissociate from monitored process. */ drvdata->pid = -1;

• drvdata->mode = CS_MODE_DISABLED;

• local_set(&csdev->mode, CS_MODE_DISABLED); spin_unlock_irqrestore(&drvdata->spinlock, flags);

dev_dbg(&csdev->dev, "ETB disabled\n"); @@ -589,7 +587,7 @@ static void etb_dump(struct etb_drvdata *drvdata) unsigned long flags; spin_lock_irqsave(&drvdata->spinlock, flags);

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) { __etb_disable_hw(drvdata); etb_dump_hw(drvdata); __etb_enable_hw(drvdata);

diff --git a/drivers/hwtracing/coresight/coresight-etm.h b/drivers/hwtracing/coresight/coresight-etm.h index 9a0d08b092ae..e02c3ea972c9 100644 --- a/drivers/hwtracing/coresight/coresight-etm.h +++ b/drivers/hwtracing/coresight/coresight-etm.h @@ -215,7 +215,6 @@ struct etm_config {

• @port_size: port size as reported by ETMCR bit 4-6 and 21.
• @arch: ETM/PTM version number.
• @use_cpu14: true if management registers need to be accessed via CP14.

• • @mode: this tracer's mode, i.e sysFS, Perf or disabled.
  • @sticky_enable: true if ETM base configuration has been done.
  • @boot_enable:true if we should start tracing at boot time.
  • @os_unlock: true if access to management registers is allowed.

@@ -238,7 +237,6 @@ struct etm_drvdata { int port_size; u8 arch; bool use_cp14;

• local_t mode; bool sticky_enable; bool boot_enable; bool os_unlock;

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c index 116a91d90ac2..29f62dfac673 100644 --- a/drivers/hwtracing/coresight/coresight-etm3x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c @@ -559,7 +559,7 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event, u32 val; struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

• val = local_cmpxchg(&drvdata->mode, CS_MODE_DISABLED, mode);

• val = local_cmpxchg(&drvdata->csdev->mode, CS_MODE_DISABLED, mode);

/* Someone is already using the tracer */ if (val) @@ -578,7 +578,7 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event, /* The tracer didn't start */ if (ret)

• local_set(&drvdata->mode, CS_MODE_DISABLED);
  

• local_set(&drvdata->csdev->mode, CS_MODE_DISABLED);
  

return ret; } @@ -672,14 +672,13 @@ static void etm_disable(struct coresight_device *csdev, struct perf_event *event) { enum cs_mode mode;

• struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

/* * For as long as the tracer isn't disabled another entity can't * change its status. As such we can read the status here without * fearing it will change under us. */

• mode = local_read(&drvdata->mode);

• mode = local_read(&csdev->mode);

switch (mode) { case CS_MODE_DISABLED: @@ -696,7 +695,7 @@ static void etm_disable(struct coresight_device *csdev, } if (mode)

• local_set(&drvdata->mode, CS_MODE_DISABLED);
  

• local_set(&csdev->mode, CS_MODE_DISABLED);
  

  }

static const struct coresight_ops_source etm_source_ops = { @@ -730,7 +729,7 @@ static int etm_starting_cpu(unsigned int cpu) etmdrvdata[cpu]->os_unlock = true; }

• if (local_read(&etmdrvdata[cpu]->mode))

• if (local_read(&etmdrvdata[cpu]->csdev->mode)) etm_enable_hw(etmdrvdata[cpu]); spin_unlock(&etmdrvdata[cpu]->spinlock); return 0;

@@ -742,7 +741,7 @@ static int etm_dying_cpu(unsigned int cpu) return 0; spin_lock(&etmdrvdata[cpu]->spinlock);

• if (local_read(&etmdrvdata[cpu]->mode))

• if (local_read(&etmdrvdata[cpu]->csdev->mode)) etm_disable_hw(etmdrvdata[cpu]); spin_unlock(&etmdrvdata[cpu]->spinlock); return 0;

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c index 2f271b7fb048..6c8429c980b1 100644 --- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c @@ -722,7 +722,7 @@ static ssize_t cntr_val_show(struct device *dev, struct etm_drvdata *drvdata = dev_get_drvdata(dev->parent); struct etm_config *config = &drvdata->config;

• if (!local_read(&drvdata->mode)) {

• if (!local_read(&drvdata->csdev->mode)) { spin_lock(&drvdata->spinlock); for (i = 0; i < drvdata->nr_cntr; i++) ret += sprintf(buf, "counter %d: %x\n",

@@ -941,7 +941,7 @@ static ssize_t seq_curr_state_show(struct device *dev, struct etm_drvdata *drvdata = dev_get_drvdata(dev->parent); struct etm_config *config = &drvdata->config;

• if (!local_read(&drvdata->mode)) {

• if (!local_read(&drvdata->csdev->mode)) { val = config->seq_curr_state; goto out; }

diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c index a1c27c901ad1..190ba569b05a 100644 --- a/drivers/hwtracing/coresight/coresight-stm.c +++ b/drivers/hwtracing/coresight/coresight-stm.c @@ -119,7 +119,6 @@ DEFINE_CORESIGHT_DEVLIST(stm_devs, "stm");

• @spinlock: only one at a time pls.
• @chs: the channels accociated to this STM.
• @stm: structure associated to the generic STM interface.

• • @mode: this tracer's mode (enum cs_mode), i.e sysFS, or disabled.
  • @traceid: value of the current ID for this component.
  • @write_bytes: Maximus bytes this STM can write at a time.
  • @stmsper: settings for register STMSPER.

@@ -136,7 +135,6 @@ struct stm_drvdata { spinlock_t spinlock; struct channel_space chs; struct stm_data stm;

• local_t mode; u8 traceid; u32 write_bytes; u32 stmsper;

@@ -201,7 +199,7 @@ static int stm_enable(struct coresight_device *csdev, struct perf_event *event, if (mode != CS_MODE_SYSFS) return -EINVAL;

• val = local_cmpxchg(&drvdata->mode, CS_MODE_DISABLED, mode);

• val = local_cmpxchg(&csdev->mode, CS_MODE_DISABLED, mode);

/* Someone is already using the tracer */ if (val) @@ -266,7 +264,7 @@ static void stm_disable(struct coresight_device *csdev, * change its status. As such we can read the status here without * fearing it will change under us. */

• if (local_read(&drvdata->mode) == CS_MODE_SYSFS) {

• if (local_read(&csdev->mode) == CS_MODE_SYSFS) { spin_lock(&drvdata->spinlock); stm_disable_hw(drvdata); spin_unlock(&drvdata->spinlock);

@@ -276,7 +274,7 @@ static void stm_disable(struct coresight_device *csdev, pm_runtime_put(csdev->dev.parent);

• local_set(&drvdata->mode, CS_MODE_DISABLED);
  

• local_set(&csdev->mode, CS_MODE_DISABLED);
  

  dev_dbg(&csdev->dev, "STM tracing disabled\n"); } }

@@ -373,7 +371,7 @@ static long stm_generic_set_options(struct stm_data *stm_data, { struct stm_drvdata *drvdata = container_of(stm_data, struct stm_drvdata, stm);

• if (!(drvdata && local_read(&drvdata->mode)))

• if (!(drvdata && local_read(&drvdata->csdev->mode))) return -EINVAL;

if (channel >= drvdata->numsp) @@ -408,7 +406,7 @@ static ssize_t notrace stm_generic_packet(struct stm_data *stm_data, struct stm_drvdata, stm); unsigned int stm_flags;

• if (!(drvdata && local_read(&drvdata->mode)))

• if (!(drvdata && local_read(&drvdata->csdev->mode))) return -EACCES;

if (channel >= drvdata->numsp) @@ -515,7 +513,7 @@ static ssize_t port_select_show(struct device *dev, struct stm_drvdata *drvdata = dev_get_drvdata(dev->parent); unsigned long val;

• if (!local_read(&drvdata->mode)) {

• if (!local_read(&drvdata->csdev->mode)) { val = drvdata->stmspscr; } else { spin_lock(&drvdata->spinlock);

@@ -541,7 +539,7 @@ static ssize_t port_select_store(struct device *dev, spin_lock(&drvdata->spinlock); drvdata->stmspscr = val;

• if (local_read(&drvdata->mode)) {

• if (local_read(&drvdata->csdev->mode)) { CS_UNLOCK(drvdata->base); /* Process as per ARM's TRM recommendation */ stmsper = readl_relaxed(drvdata->base + STMSPER);

@@ -562,7 +560,7 @@ static ssize_t port_enable_show(struct device *dev, struct stm_drvdata *drvdata = dev_get_drvdata(dev->parent); unsigned long val;

• if (!local_read(&drvdata->mode)) {

• if (!local_read(&drvdata->csdev->mode)) { val = drvdata->stmsper; } else { spin_lock(&drvdata->spinlock);

@@ -588,7 +586,7 @@ static ssize_t port_enable_store(struct device *dev, spin_lock(&drvdata->spinlock); drvdata->stmsper = val;

• if (local_read(&drvdata->mode)) {

• if (local_read(&drvdata->csdev->mode)) { CS_UNLOCK(drvdata->base); writel_relaxed(drvdata->stmsper, drvdata->base + STMSPER); CS_LOCK(drvdata->base);

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c index 7ec5365e2b64..e5d47f61f9f3 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-core.c +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c @@ -558,7 +558,7 @@ static void tmc_shutdown(struct amba_device *adev) spin_lock_irqsave(&drvdata->spinlock, flags);

• if (drvdata->mode == CS_MODE_DISABLED)

• if (local_read(&drvdata->csdev->mode) == CS_MODE_DISABLED) goto out;

if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index 7406b65e2cdd..2a7e516052a2 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -89,7 +89,7 @@ static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata) * When operating in sysFS mode the content of the buffer needs to be * read before the TMC is disabled. */

• if (drvdata->mode == CS_MODE_SYSFS)

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) tmc_etb_dump_hw(drvdata); tmc_disable_hw(drvdata);

@@ -205,7 +205,7 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev) * sink is already enabled no memory is needed and the HW need not be * touched. */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&csdev->mode) == CS_MODE_SYSFS) { atomic_inc(&csdev->refcnt); goto out; }

@@ -228,7 +228,7 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev) ret = tmc_etb_enable_hw(drvdata); if (!ret) {

• drvdata->mode = CS_MODE_SYSFS;
  

• local_set(&csdev->mode, CS_MODE_SYSFS);
  

  atomic_inc(&csdev->refcnt); } else { /* Free up the buffer if we failed to enable */

@@ -262,7 +262,7 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data) * No need to continue if the ETB/ETF is already operated * from sysFS. */

• if (drvdata->mode == CS_MODE_SYSFS) {
  

• if (local_read(&csdev->mode) == CS_MODE_SYSFS) {
  ret = -EBUSY;
  break;
  

  }

@@ -292,7 +292,7 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, void *data) if (!ret) { /* Associate with monitored process. */ drvdata->pid = pid;

• 	drvdata->mode = CS_MODE_PERF;
  

• 	local_set(&csdev->mode, CS_MODE_PERF);
  atomic_inc(&csdev->refcnt);
  

  } } while (0);

@@ -344,11 +344,11 @@ static int tmc_disable_etf_sink(struct coresight_device *csdev) } /* Complain if we (somehow) got out of sync */

• WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);

• WARN_ON_ONCE(local_read(&csdev->mode) == CS_MODE_DISABLED); tmc_etb_disable_hw(drvdata); /* Dissociate from monitored process. */ drvdata->pid = -1;

• drvdata->mode = CS_MODE_DISABLED;

• local_set(&csdev->mode, CS_MODE_DISABLED);

spin_unlock_irqrestore(&drvdata->spinlock, flags); @@ -374,7 +374,7 @@ static int tmc_enable_etf_link(struct coresight_device *csdev, if (atomic_read(&csdev->refcnt) == 0) { ret = tmc_etf_enable_hw(drvdata); if (!ret) {

• 	drvdata->mode = CS_MODE_SYSFS;
  

• 	local_set(&csdev->mode, CS_MODE_SYSFS);
  first_enable = true;
  

  } }

@@ -403,7 +403,7 @@ static void tmc_disable_etf_link(struct coresight_device *csdev, if (atomic_dec_return(&csdev->refcnt) == 0) { tmc_etf_disable_hw(drvdata);

• drvdata->mode = CS_MODE_DISABLED;
  

• local_set(&csdev->mode, CS_MODE_DISABLED);
  

  last_disable = true; } spin_unlock_irqrestore(&drvdata->spinlock, flags);

@@ -483,7 +483,7 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev, return 0; /* This shouldn't happen */

• if (WARN_ON_ONCE(drvdata->mode != CS_MODE_PERF))

• if (WARN_ON_ONCE(local_read(&csdev->mode) != CS_MODE_PERF)) return 0;

spin_lock_irqsave(&drvdata->spinlock, flags); @@ -629,7 +629,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata) } /* Don't interfere if operated from Perf */

• if (drvdata->mode == CS_MODE_PERF) {

• if (local_read(&drvdata->csdev->mode) == CS_MODE_PERF) { ret = -EINVAL; goto out; }

@@ -641,7 +641,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata) } /* Disable the TMC if need be */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) { /* There is no point in reading a TMC in HW FIFO mode */ mode = readl_relaxed(drvdata->base + TMC_MODE); if (mode != TMC_MODE_CIRCULAR_BUFFER) {

@@ -673,7 +673,7 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata) spin_lock_irqsave(&drvdata->spinlock, flags); /* Re-enable the TMC if need be */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) { /* There is no point in reading a TMC in HW FIFO mode */ mode = readl_relaxed(drvdata->base + TMC_MODE); if (mode != TMC_MODE_CIRCULAR_BUFFER) {

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index af02ba5d5f15..3dc989d4fcab 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -1143,7 +1143,7 @@ static void __tmc_etr_disable_hw(struct tmc_drvdata *drvdata) * When operating in sysFS mode the content of the buffer needs to be * read before the TMC is disabled. */

• if (drvdata->mode == CS_MODE_SYSFS)

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) tmc_etr_sync_sysfs_buf(drvdata);

tmc_disable_hw(drvdata); @@ -1189,7 +1189,7 @@ static struct etr_buf *tmc_etr_get_sysfs_buffer(struct coresight_device *csdev) spin_lock_irqsave(&drvdata->spinlock, flags); }

• if (drvdata->reading || drvdata->mode == CS_MODE_PERF) {

• if (drvdata->reading || local_read(&csdev->mode) == CS_MODE_PERF) { ret = -EBUSY; goto out; }

@@ -1230,14 +1230,14 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev) * sink is already enabled no memory is needed and the HW need not be * touched, even if the buffer size has changed. */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&csdev->mode) == CS_MODE_SYSFS) { atomic_inc(&csdev->refcnt); goto out; }

ret = tmc_etr_enable_hw(drvdata, sysfs_buf); if (!ret) {

• drvdata->mode = CS_MODE_SYSFS;
  

• local_set(&csdev->mode, CS_MODE_SYSFS);
  

  atomic_inc(&csdev->refcnt); }

@@ -1652,7 +1652,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data) spin_lock_irqsave(&drvdata->spinlock, flags); /* Don't use this sink if it is already claimed by sysFS */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&csdev->mode) == CS_MODE_SYSFS) { rc = -EBUSY; goto unlock_out; }

@@ -1684,7 +1684,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data) if (!rc) { /* Associate with monitored process. */ drvdata->pid = pid;

• drvdata->mode = CS_MODE_PERF;
  

• local_set(&csdev->mode, CS_MODE_PERF);
  

  drvdata->perf_buf = etr_perf->etr_buf; atomic_inc(&csdev->refcnt); }

@@ -1725,11 +1725,11 @@ static int tmc_disable_etr_sink(struct coresight_device *csdev) } /* Complain if we (somehow) got out of sync */

• WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);

• WARN_ON_ONCE(local_read(&csdev->mode) == CS_MODE_DISABLED); tmc_etr_disable_hw(drvdata); /* Dissociate from monitored process. */ drvdata->pid = -1;

• drvdata->mode = CS_MODE_DISABLED;

• local_set(&csdev->mode, CS_MODE_DISABLED); /* Reset perf specific data */ drvdata->perf_buf = NULL;

@@ -1777,7 +1777,7 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata) } /* Disable the TMC if we are trying to read from a running session. */

• if (drvdata->mode == CS_MODE_SYSFS)

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) __tmc_etr_disable_hw(drvdata);

drvdata->reading = true; @@ -1799,7 +1799,7 @@ int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata) spin_lock_irqsave(&drvdata->spinlock, flags); /* RE-enable the TMC if need be */

• if (drvdata->mode == CS_MODE_SYSFS) {

• if (local_read(&drvdata->csdev->mode) == CS_MODE_SYSFS) { /*
  • The trace run will continue with the same allocated trace
  • buffer. Since the tracer is still enabled drvdata::buf can't

diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h index 8dcb426ac3e7..cef979c897e6 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.h +++ b/drivers/hwtracing/coresight/coresight-tmc.h @@ -178,7 +178,6 @@ struct etr_buf {

• @size: trace buffer size for this TMC (common for all modes).
• @max_burst_size: The maximum burst size that can be initiated by

• TMC-ETR on AXI bus.
  

• • @mode: how this TMC is being used.
  • @config_type: TMC variant, must be of type @tmc_config_type.
  • @memwidth: width of the memory interface databus, in bytes.
  • @trigger_cntr: amount of words to store after a trigger.

@@ -203,7 +202,6 @@ struct tmc_drvdata { u32 len; u32 size; u32 max_burst_size;

• u32 mode; enum tmc_config_type config_type; enum tmc_mem_intf_width memwidth; u32 trigger_cntr;

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c index 10e886455b8b..1a8c64645b92 100644 --- a/drivers/hwtracing/coresight/ultrasoc-smb.c +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c @@ -207,11 +207,11 @@ static void smb_enable_sysfs(struct coresight_device *csdev) { struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);

• if (drvdata->mode != CS_MODE_DISABLED)

• if (local_read(&csdev->mode) != CS_MODE_DISABLED) return;

smb_enable_hw(drvdata);

• drvdata->mode = CS_MODE_SYSFS;

• local_set(&csdev->mode, CS_MODE_SYSFS); }

static int smb_enable_perf(struct coresight_device *csdev, void *data) @@ -234,7 +234,7 @@ static int smb_enable_perf(struct coresight_device *csdev, void *data) if (drvdata->pid == -1) { smb_enable_hw(drvdata); drvdata->pid = pid;

• drvdata->mode = CS_MODE_PERF;
  

• local_set(&csdev->mode, CS_MODE_PERF);
  

  }

return 0; @@ -253,7 +253,8 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode, return -EBUSY; /* Do nothing, the SMB is already enabled as other mode */

• if (drvdata->mode != CS_MODE_DISABLED && drvdata->mode != mode)

• if (local_read(&csdev->mode) != CS_MODE_DISABLED &&

•    local_read(&csdev->mode) != mode)
  

  return -EBUSY;

switch (mode) { @@ -289,13 +290,13 @@ static int smb_disable(struct coresight_device *csdev) return -EBUSY; /* Complain if we (somehow) got out of sync */

• WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);

• WARN_ON_ONCE(local_read(&csdev->mode) == CS_MODE_DISABLED);

smb_disable_hw(drvdata); /* Dissociate from the target process. */ drvdata->pid = -1;

• drvdata->mode = CS_MODE_DISABLED;

• local_set(&csdev->mode, CS_MODE_DISABLED); dev_dbg(&csdev->dev, "Ultrasoc SMB disabled\n");

return 0; diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h index 82a44c14a882..a91d39cfccb8 100644 --- a/drivers/hwtracing/coresight/ultrasoc-smb.h +++ b/drivers/hwtracing/coresight/ultrasoc-smb.h @@ -109,7 +109,6 @@ struct smb_data_buffer {

• @reading: Synchronise user space access to SMB buffer.
• @pid: Process ID of the process being monitored by the

• session that is using this component.
  

• • @mode: How this SMB is being used, perf mode or sysfs mode.
  */ struct smb_drv_data { void __iomem *base;

@@ -119,7 +118,6 @@ struct smb_drv_data { spinlock_t spinlock; bool reading; pid_t pid;

• enum cs_mode mode; };

#endif diff --git a/include/linux/coresight.h b/include/linux/coresight.h index 65131bfbd904..ba817f563ff7 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -226,6 +226,11 @@ struct coresight_sysfs_link {

• by @coresight_ops.
  

• @access: Device i/o access abstraction for this device.
• @dev: The device entity associated to this component.

• • @mode: This tracer's mode, i.e sysFS, Perf or disabled. This is

• • actually an 'enum cs_mode', but is stored in an atomic type.
    

• • This is always accessed through local_read() and local_set(),
    

• • but wherever it's done from within the Coresight device's lock,
    

• • a non-atomic read would also work.
    

By abstracting it, we could enforce this change. Eitherways, the change as such is fine by me.

Suzuki

• @refcnt: keep track of what is in use.
• @orphan: true if the component has connections that haven't been linked.
• @enable: 'true' if component is currently part of an active path.

@@ -252,6 +257,7 @@ struct coresight_device { const struct coresight_ops *ops; struct csdev_access access; struct device dev;

• local_t mode; atomic_t refcnt; bool orphan; bool enable;

On 09/01/2024 10:38, Suzuki K Poulose wrote:

Hi James

On 12/12/2023 15:54, James Clark wrote:

...

These are a bit annoying to keep up to date when the function signatures change. But if CONFIG_CORESIGHT isn't enabled, then they're not used anyway so just delete them.

Have you tried building an arm32 kernel with this change in ? Looks like arch/arm/kernel/hw_breakpoint.c includes linux/coresight.h and a build with CONFIG_CORSIGHT=n might break the build ? So is

arm32 and CONFIG_CORESIGHT=n works because hw_breakpoint.c doesn't use any of those symbols, only #defines that were outside the #if IS_ENABLED(CONFIG_CORESIGHT), specifically CORESIGHT_UNLOCK.

drivers/accel/habanalabs/common/habanalabs.h. Now, I am not sure if they

habanalabs is interesting, it depends on X86_64, but CONFIG_CORESIGHT depends on ARM || ARM64, so I think we can assume it's also only looking for #defines and inlines, and not actual code.

Either way I can't find any build config that actually ever built this, meaning it's always been dead code. I would have expected some build robot to have flagged an error by now as I've seen that on other coresight patches.

really need it (even if they do, we may be able to remove the dependency on the header file.

They do really need it, also for the CORESIGHT_UNLOCK definition, but not any functions.

Suzuki

...

Signed-off-by: James Clark james.clark@arm.com

include/linux/coresight.h | 79 ---------------------------------------   1 file changed, 79 deletions(-)

diff --git a/include/linux/coresight.h b/include/linux/coresight.h index 4400d554a16b..c5be46d7f85c 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -391,8 +391,6 @@ struct coresight_ops {       const struct coresight_ops_helper *helper_ops;   };   -#if IS_ENABLED(CONFIG_CORESIGHT)

static inline u32 csdev_access_relaxed_read32(struct csdev_access *csa,                             u32 offset)   { @@ -611,83 +609,6 @@ void coresight_relaxed_write64(struct coresight_device *csdev,                      u64 val, u32 offset);   void coresight_write64(struct coresight_device *csdev, u64 val, u32 offset);   -#else -static inline struct coresight_device * -coresight_register(struct coresight_desc *desc) { return NULL; } -static inline void coresight_unregister(struct coresight_device *csdev) {} -static inline int -coresight_enable_sysfs(struct coresight_device *csdev) { return -ENOSYS; } -static inline void coresight_disable_sysfs(struct coresight_device *csdev) {}

-static inline int coresight_timeout(struct csdev_access *csa, u32 offset, -                    int position, int value) -{ -    return 1; -}

-static inline int coresight_claim_device_unlocked(struct coresight_device *csdev) -{ -    return -EINVAL; -}

-static inline int coresight_claim_device(struct coresight_device *csdev) -{ -    return -EINVAL; -}

-static inline void coresight_disclaim_device(struct coresight_device *csdev) {} -static inline void coresight_disclaim_device_unlocked(struct coresight_device *csdev) {}

-static inline bool coresight_loses_context_with_cpu(struct device *dev) -{ -    return false; -}

-static inline u32 coresight_relaxed_read32(struct coresight_device *csdev, u32 offset) -{ -    WARN_ON_ONCE(1); -    return 0; -}

-static inline u32 coresight_read32(struct coresight_device *csdev, u32 offset) -{ -    WARN_ON_ONCE(1); -    return 0; -}

-static inline void coresight_write32(struct coresight_device *csdev, u32 val, u32 offset) -{ -}

-static inline void coresight_relaxed_write32(struct coresight_device *csdev, -                         u32 val, u32 offset) -{ -}

-static inline u64 coresight_relaxed_read64(struct coresight_device *csdev, -                       u32 offset) -{ -    WARN_ON_ONCE(1); -    return 0; -}

-static inline u64 coresight_read64(struct coresight_device *csdev, u32 offset) -{ -    WARN_ON_ONCE(1); -    return 0; -}

-static inline void coresight_relaxed_write64(struct coresight_device *csdev, -                         u64 val, u32 offset) -{ -}

-static inline void coresight_write64(struct coresight_device *csdev, u64 val, u32 offset) -{ -}

-#endif        /* IS_ENABLED(CONFIG_CORESIGHT) */

extern int coresight_get_cpu(struct device *dev);     struct coresight_platform_data *coresight_get_platform_data(struct device *dev);

On 08/01/2024 14:42, Suzuki K Poulose wrote:

Hi James

+Cc: Tao Zhang quic_taozha@quicinc.com +Cc: Mao Jinlong quic_jinlmao@quicinc.com

On 12/12/2023 15:54, James Clark wrote:

...

'enable', which probably should have been 'enabled', is only ever read in the core code in relation to controlling sources, and specifically only sources in sysfs mode. Confusingly it's not labelled as such and relying on it can be a source of bugs like the one fixed by commit 078dbba3f0c9 ("coresight: Fix crash when Perf and sysfs modes are used concurrently").

Most importantly, it can only be used when the coresight_mutex is held which is only done when enabling and disabling paths in sysfs mode, and not Perf mode.

I think we may be able to relax this a bit for the syfs. The sole reason for holding the mutex is for the "build_path" (and get_enabled_sink) where we need to make sure that no devices are removed/added. We hold necessary refcount on the device and the module (via coresight_grab_device()). After which, we should be able to release the mutex and perform the rest without it in coresight_enable()

After looking at the per-sink trace ID maps a bit more, I'm not sure if it will be worth the mental effort and risk to relax the sysfs locking right now.

We also currently have other things like writing to the global tracer_path which are outside of build_path/get_enabled_sink. But for the per-sink maps change we'll also have some tracking for sysfs mode about which sink map was used for each source and sink. And this state will be accessed across multiple sources, and after building the path, so it makes sense to leave the locking as-is for now IMO.

I also can't see a realistic gain from doing it, most sysfs use cases would be done from a single threaded script. Maybe in the future we could do the change to move the per-device locks into struct coresight_device, and then the core code can use them for things that need to be locked, but don't need the full coresight_mutex. And then that would also work for the per-sink case. But at the moment each device has its own lock so that's difficult.

...

So to prevent its usage spreading and leaking out to other devices, remove it.

It's use is equivalent to checking if the mode is currently sysfs, as due to the coresight_mutex lock, mode == CS_MODE_SYSFS can only become true or untrue when that lock is held, and when mode == CS_MODE_SYSFS the device is both enabled and in sysfs mode.

All of the above makes sense and looks good to me.

...

The one place it was used outside of the core code is in TPDA, but that pattern is more appropriately represented using refcounts inside the device's own spinlock.

But, I think we can clean up this code a bit more better. See below.

...

Signed-off-by: James Clark james.clark@arm.com

drivers/hwtracing/coresight/coresight-core.c | 86 +++++++-------------   drivers/hwtracing/coresight/coresight-tpda.c | 12 ++-   include/linux/coresight.h                    |  2 -   3 files changed, 38 insertions(+), 62 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index ab226441e5f4..1d0bd1586590 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -279,29 +279,18 @@ EXPORT_SYMBOL_GPL(coresight_add_helper);   static int coresight_enable_sink(struct coresight_device *csdev,                    enum cs_mode mode, void *data)   { -    int ret = sink_ops(csdev)->enable(csdev, mode, data);

-    if (ret) -        return ret;

-    csdev->enable = true;

-    return 0; +    return sink_ops(csdev)->enable(csdev, mode, data);   }     static void coresight_disable_sink(struct coresight_device *csdev)   { -    int ret = sink_ops(csdev)->disable(csdev); -    if (ret) -        return; -    csdev->enable = false; +    sink_ops(csdev)->disable(csdev);   }     static int coresight_enable_link(struct coresight_device *csdev,                    struct coresight_device *parent,                    struct coresight_device *child)   { -    int ret = 0;       int link_subtype;       struct coresight_connection *inconn, *outconn;   @@ -317,19 +306,13 @@ static int coresight_enable_link(struct coresight_device *csdev,       if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT && IS_ERR(outconn))           return PTR_ERR(outconn);   -    ret = link_ops(csdev)->enable(csdev, inconn, outconn); -    if (!ret) -        csdev->enable = true;

-    return ret; +    return link_ops(csdev)->enable(csdev, inconn, outconn);   }     static void coresight_disable_link(struct coresight_device *csdev,                      struct coresight_device *parent,                      struct coresight_device *child)   { -    int i; -    int link_subtype;       struct coresight_connection *inconn, *outconn;         if (!parent || !child) @@ -337,26 +320,8 @@ static void coresight_disable_link(struct coresight_device *csdev,         inconn = coresight_find_out_connection(parent, csdev);       outconn = coresight_find_out_connection(csdev, child); -    link_subtype = csdev->subtype.link_subtype;         link_ops(csdev)->disable(csdev, inconn, outconn);

-    if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG) { -        for (i = 0; i < csdev->pdata->nr_inconns; i++) -            if (atomic_read(&csdev->pdata->in_conns[i]->dest_refcnt) != -                0) -                return; -    } else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT) { -        for (i = 0; i < csdev->pdata->nr_outconns; i++) -            if (atomic_read(&csdev->pdata->out_conns[i]->src_refcnt) != -                0) -                return; -    } else { -        if (atomic_read(&csdev->refcnt) != 0) -            return; -    }

-    csdev->enable = false;   }     int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode, @@ -364,11 +329,16 @@ int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode,   {       int ret;   -    if (!csdev->enable) { +    /* +     * Comparison with CS_MODE_SYSFS works without taking any device +     * specific spinlock because the truthyness of that comparison can only +     * change with coresight_mutex held, which we already have here. +     */ +    lockdep_assert_held(&coresight_mutex); +    if (local_read(&csdev->mode) != CS_MODE_SYSFS) {           ret = source_ops(csdev)->enable(csdev, data, mode);           if (ret)               return ret; -        csdev->enable = true;       }         atomic_inc(&csdev->refcnt); @@ -385,22 +355,12 @@ static bool coresight_is_helper(struct coresight_device *csdev)   static int coresight_enable_helper(struct coresight_device *csdev,                      enum cs_mode mode, void *data)   { -    int ret = helper_ops(csdev)->enable(csdev, mode, data);

-    if (ret) -        return ret;

-    csdev->enable = true; -    return 0; +    return helper_ops(csdev)->enable(csdev, mode, data);   }     static void coresight_disable_helper(struct coresight_device *csdev)   { -    int ret = helper_ops(csdev)->disable(csdev, NULL);

-    if (ret) -        return; -    csdev->enable = false; +    helper_ops(csdev)->disable(csdev, NULL);   }     static void coresight_disable_helpers(struct coresight_device *csdev) @@ -445,11 +405,15 @@ EXPORT_SYMBOL_GPL(coresight_disable_source);   static bool coresight_disable_source_sysfs(struct coresight_device *csdev,                          void *data)   { +    lockdep_assert_held(&coresight_mutex); +    if (local_read(&csdev->mode) != CS_MODE_SYSFS) +        return false;

if (atomic_dec_return(&csdev->refcnt) == 0) {           coresight_disable_source(csdev, data); -        csdev->enable = false; +        return true;       } -    return !csdev->enable; +    return false;   }     /* @@ -1097,7 +1061,13 @@ int coresight_enable(struct coresight_device *csdev)       if (ret)           goto out;   -    if (csdev->enable) { +    /* +     * mode == SYSFS implies that it's already enabled. Don't look at the +     * refcount to determine this because we don't claim the source until +     * coresight_enable_source() so can still race with Perf mode which +     * doesn't hold coresight_mutex. +     */ +    if (local_read(&csdev->mode) == CS_MODE_SYSFS) {           /*            * There could be multiple applications driving the software            * source. So keep the refcount for each such user when the @@ -1183,7 +1153,7 @@ void coresight_disable(struct coresight_device *csdev)       if (ret)           goto out;   -    if (!csdev->enable || !coresight_disable_source_sysfs(csdev, NULL)) +    if (!coresight_disable_source_sysfs(csdev, NULL))           goto out;         switch (csdev->subtype.source_subtype) { @@ -1249,7 +1219,9 @@ static ssize_t enable_source_show(struct device *dev,   {       struct coresight_device *csdev = to_coresight_device(dev);   -    return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->enable); +    guard(mutex)(&coresight_mutex); +    return scnprintf(buf, PAGE_SIZE, "%u\n", +             local_read(&csdev->mode) == CS_MODE_SYSFS);   }     static ssize_t enable_source_store(struct device *dev, diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c index 5f82737c37bb..65c70995ab00 100644 --- a/drivers/hwtracing/coresight/coresight-tpda.c +++ b/drivers/hwtracing/coresight/coresight-tpda.c @@ -148,7 +148,11 @@ static int __tpda_enable(struct tpda_drvdata *drvdata, int port)         CS_UNLOCK(drvdata->base);   -    if (!drvdata->csdev->enable) +    /* +     * Only do pre-port enable for first port that calls enable when the +     * device's main refcount is still 0 +     */ +    if (!atomic_read(&drvdata->csdev->refcnt))           tpda_enable_pre_port(drvdata);

Relying on the "csdev->enable" to do pre-port configuration looks like a complete hack to me. This could have been performed once and for all during the probe time, at say, tpda_init_default_data(). That value is (drvdata->atid) never updated and need not be re-written  unless the value is lost during a power idle.

Mao, Tao, are you able to confirm this ? If that is the case, we don't need this csdev->refcnt.

"unless the value is lost during a power idle."

That one might be a reason to do it. I suppose it makes sense to write all the registers on enable, but not to keep re-writing the trace ID again for every port that's used.

...

ret = tpda_enable_port(drvdata, port); @@ -169,6 +173,7 @@ static int tpda_enable(struct coresight_device *csdev,           ret = __tpda_enable(drvdata, in->dest_port);           if (!ret) {               atomic_inc(&in->dest_refcnt); +            atomic_inc(&csdev->refcnt);               dev_dbg(drvdata->dev, "TPDA inport %d enabled.\n", in->dest_port);           }       } @@ -197,9 +202,10 @@ static void tpda_disable(struct coresight_device *csdev,       struct tpda_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);         spin_lock(&drvdata->spinlock); -    if (atomic_dec_return(&in->dest_refcnt) == 0) +    if (atomic_dec_return(&in->dest_refcnt) == 0) {           __tpda_disable(drvdata, in->dest_port);

+        atomic_dec(&csdev->refcnt);

If we need this, then: This should be performed outside the if () isn't it ?

e.g.,

Operation:        in_conn->refcnt        csdev->refcnt port_enable : port0    0 - > 1            0 - > 1 port_enable : port0     1 - > 2            1 - > 2

I didn't get 1 -> 2 here, because the in->dest_refcnt is only incremented once if it was already 0 (although it is once for each port):

if (atomic_read(&in->dest_refcnt) == 0) { ret = __tpda_enable(drvdata, in->dest_port); if (!ret) { atomic_inc(&in->dest_refcnt);

That basically makes csdev->refcnt count how many ports were used, but each port's refcount can only be used once. And then when each port is disabled csdev->refcnt returns to zero on the last port.

port_disable: port0    2 - > 1            2 (no change) port_disable: port0    1 - > 0            2 - > 1

As you can see the csdev->refcnt skipped a dec.

Suzuki

...

+    }       spin_unlock(&drvdata->spinlock);         dev_dbg(drvdata->dev, "TPDA inport %d disabled\n", in->dest_port); diff --git a/include/linux/coresight.h b/include/linux/coresight.h index ba817f563ff7..46e6667f72ce 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -233,7 +233,6 @@ struct coresight_sysfs_link {    *        a non-atomic read would also work.    * @refcnt:    keep track of what is in use.    * @orphan:    true if the component has connections that haven't been linked.

• • @enable:    'true' if component is currently part of an active path.

* @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs    *        by writing a 1 to the 'enable_sink' file.  A sink can be    *        activated but not yet enabled.  Enabling for a _sink_ happens @@ -260,7 +259,6 @@ struct coresight_device {       local_t    mode;       atomic_t refcnt;       bool orphan; -    bool enable;       /* sink specific fields */       bool sysfs_sink_activated;       struct dev_ext_attribute *ea;

On 08/01/2024 11:21, Suzuki K Poulose wrote:

Hi James,

On 12/12/2023 15:53, James Clark wrote:

...

Activated has the specific meaning of a sink that's selected for use by the user via sysfs. But comments in some code that's shared by Perf use the same word, so in those cases change them to just say "selected" instead. With selected implying either via Perf or "activated" via sysfs.

coresight_get_enabled_sink() doesn't actually get an enabled sink, it only gets an activated one, so change that too.

These changes look good to me. Please see a minor nit below.

...

And change the activated variable name to include "sysfs" so it can't be confused as a general status.

Signed-off-by: James Clark james.clark@arm.com

drivers/hwtracing/coresight/coresight-core.c | 51 ++++++++------------   drivers/hwtracing/coresight/coresight-priv.h |  2 -   include/linux/coresight.h                    | 14 +++---   3 files changed, 27 insertions(+), 40 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 965bb6d4e1bf..f79aa9ff9b64 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -500,7 +500,7 @@ static void coresight_disable_path_from(struct list_head *path,           /*            * ETF devices are tricky... They can be a link or a sink,            * depending on how they are configured.  If an ETF has been -         * "activated" it will be configured as a sink, otherwise +         * selected as a sink it will be configured as a sink, otherwise            * go ahead with the link configuration.            */           if (type == CORESIGHT_DEV_TYPE_LINKSINK) @@ -578,7 +578,7 @@ int coresight_enable_path(struct list_head *path, enum cs_mode mode,           /*            * ETF devices are tricky... They can be a link or a sink,            * depending on how they are configured.  If an ETF has been -         * "activated" it will be configured as a sink, otherwise +         * selected as a sink it will be configured as a sink, otherwise            * go ahead with the link configuration.            */           if (type == CORESIGHT_DEV_TYPE_LINKSINK) @@ -635,15 +635,21 @@ struct coresight_device *coresight_get_sink(struct list_head *path)       return csdev;   }   +/**

• • coresight_find_activated_sysfs_sink - returns the first sink

activated via

• • sysfs using connection based search starting from the source

reference.

• • @csdev: Coresight source device reference
• */

static struct coresight_device * -coresight_find_enabled_sink(struct coresight_device *csdev) +coresight_find_activated_sysfs_sink(struct coresight_device *csdev)   {       int i;       struct coresight_device *sink = NULL;         if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||            csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) && -         csdev->activated) +         csdev->sysfs_sink_activated)           return csdev;         /* @@ -654,7 +660,7 @@ coresight_find_enabled_sink(struct coresight_device *csdev)             child_dev = csdev->pdata->out_conns[i]->dest_dev;           if (child_dev) -            sink = coresight_find_enabled_sink(child_dev); +            sink = coresight_find_activated_sysfs_sink(child_dev);           if (sink)               return sink;       } @@ -662,21 +668,6 @@ coresight_find_enabled_sink(struct coresight_device *csdev)       return NULL;   }   -/**

• • coresight_get_enabled_sink - returns the first enabled sink using
• • connection based search starting from the source reference
• • @source: Coresight source device reference
• */

-struct coresight_device * -coresight_get_enabled_sink(struct coresight_device *source) -{ -    if (!source) -        return NULL;

-    return coresight_find_enabled_sink(source); -}

static int coresight_sink_by_id(struct device *dev, const void *data)   {       struct coresight_device *csdev = to_coresight_device(dev); @@ -810,11 +801,10 @@ static void coresight_drop_device(struct coresight_device *csdev)    * @sink:    The final sink we want in this path.    * @path:    The list to add devices to.    *

• • The tree of Coresight device is traversed until an activated sink is
• • found.  From there the sink is added to the list along with all the
• • devices that led to that point - the end result is a list from source
• • to sink. In that list the source is the first device and the sink the
• • last one.

• • The tree of Coresight device is traversed until the selected sink

is found.

minor nit: s/until the selected/until *a* selected/

There could be multiple sinks activated that can be reached from the source. But we choose the "closest" possible selected sink for a source. So, it may be better to drop "the".

For _coresight_build_path() this isn't strictly true because the sink is passed in as an argument so there is only one. The only function that behaves like that is coresight_find_activated_sysfs_sink() which already seems to be documented properly.

To clarify it I'll just change "until the selected" to "until @sink" is found.

...

• • From there the sink is added to the list along with all the

devices that led

• • to that point - the end result is a list from source to sink. In

that list

• • the source is the first device and the sink the last one.

*/   static int _coresight_build_path(struct coresight_device *csdev,                    struct coresight_device *sink, @@ -824,7 +814,7 @@ static int _coresight_build_path(struct coresight_device *csdev,       bool found = false;       struct coresight_node *node;   -    /* An activated sink has been found.  Enqueue the element */ +    /* The selected sink has been found.  Enqueue the element */

Similarly here.

Same as above.

Rest looks fine to me.

Suzuki

...

if (csdev == sink)           goto out;   @@ -1145,7 +1135,7 @@ int coresight_enable(struct coresight_device *csdev)           goto out;       }   -    sink = coresight_get_enabled_sink(csdev); +    sink = coresight_find_activated_sysfs_sink(csdev);       if (!sink) {           ret = -EINVAL;           goto out; @@ -1259,7 +1249,7 @@ static ssize_t enable_sink_show(struct device *dev,   {       struct coresight_device *csdev = to_coresight_device(dev);   -    return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->activated); +    return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->sysfs_sink_activated);   }     static ssize_t enable_sink_store(struct device *dev, @@ -1274,10 +1264,7 @@ static ssize_t enable_sink_store(struct device *dev,       if (ret)           return ret;   -    if (val) -        csdev->activated = true; -    else -        csdev->activated = false; +    csdev->sysfs_sink_activated = !!val;         return size;   diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h index 30c051055e54..ced5be05a527 100644 --- a/drivers/hwtracing/coresight/coresight-priv.h +++ b/drivers/hwtracing/coresight/coresight-priv.h @@ -130,8 +130,6 @@ void coresight_disable_path(struct list_head *path);   int coresight_enable_path(struct list_head *path, enum cs_mode mode,                 void *sink_data);   struct coresight_device *coresight_get_sink(struct list_head *path); -struct coresight_device * -coresight_get_enabled_sink(struct coresight_device *source);   struct coresight_device *coresight_get_sink_by_id(u32 id);   struct coresight_device *   coresight_find_default_sink(struct coresight_device *csdev); diff --git a/include/linux/coresight.h b/include/linux/coresight.h index a4cb7dd6ca23..65131bfbd904 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -229,10 +229,12 @@ struct coresight_sysfs_link {    * @refcnt:    keep track of what is in use.    * @orphan:    true if the component has connections that haven't been linked.    * @enable:    'true' if component is currently part of an active path.

• • @activated:    'true' only if a _sink_ has been activated.  A sink

can be

• *        activated but not yet enabled.  Enabling for a _sink_
• *        happens when a source has been selected and a path is enabled
• *        from source to that sink.

• • @sysfs_sink_activated: 'true' when a sink has been selected for

use via sysfs

• *        by writing a 1 to the 'enable_sink' file.  A sink can be
• *        activated but not yet enabled.  Enabling for a _sink_ happens
• *        when a source has been selected and a path is enabled from
• *        source to that sink. A sink can also become enabled but not
• *        activated if it's used via Perf.

* @ea:        Device attribute for sink representation under PMU directory.    * @def_sink:    cached reference to default sink found for this device.    * @nr_links:   number of sysfs links created to other components from this @@ -252,9 +254,9 @@ struct coresight_device {       struct device dev;       atomic_t refcnt;       bool orphan; -    bool enable;    /* true only if configured as part of a path */ +    bool enable;       /* sink specific fields */ -    bool activated;    /* true only if a sink is part of a path */ +    bool sysfs_sink_activated;       struct dev_ext_attribute *ea;       struct coresight_device *def_sink;       /* sysfs links between components */