Coresight_claim_device() is called in cti_starting_cpu() only when CTI is enabled while coresight_disclaim_device() is called uncontionally in cti_dying_cpu(). This triggered below WARNING. Only call disclaim device when CTI device is enabled to fix it.
[ 75.989643] WARNING: CPU: 1 PID: 14 at kernel/drivers/hwtracing/coresight/coresight.c:209 coresight_disclaim_device_unlocked+0x10/0x24 [ 75.989697] CPU: 1 PID: 14 Comm: migration/1 Not tainted 5.9.0-rc1-gff1304be0a05-dirty #21 [ 75.989709] Hardware name: Thundercomm Dragonboard 845c (DT) [ 75.989737] pstate: 80c00085 (Nzcv daIf +PAN +UAO BTYPE=--) [ 75.989758] pc : coresight_disclaim_device_unlocked+0x10/0x24 [ 75.989775] lr : coresight_disclaim_device+0x24/0x38 [ 75.989783] sp : ffff800011cd3c90 . [ 75.990018] Call trace: [ 75.990041] coresight_disclaim_device_unlocked+0x10/0x24 [ 75.990066] cti_dying_cpu+0x34/0x4c [ 75.990101] cpuhp_invoke_callback+0x84/0x1e0 [ 75.990121] take_cpu_down+0x90/0xe0 [ 75.990154] multi_cpu_stop+0x134/0x160 [ 75.990171] cpu_stopper_thread+0xb0/0x13c [ 75.990196] smpboot_thread_fn+0x1c4/0x270 [ 75.990222] kthread+0x128/0x154 [ 75.990251] ret_from_fork+0x10/0x18
Fixes: e9b880581d55 ("coresight: cti: Add CPU Hotplug handling to CTI driver") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org --- drivers/hwtracing/coresight/coresight-cti.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 3ccc703dc940..d6fea6efec71 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -742,7 +742,8 @@ static int cti_dying_cpu(unsigned int cpu)
spin_lock(&drvdata->spinlock); drvdata->config.hw_powered = false; - coresight_disclaim_device(drvdata->base); + if (drvdata->config.hw_enabled) + coresight_disclaim_device(drvdata->base); spin_unlock(&drvdata->spinlock); return 0; }
Below BUG is triggered by call pm_runtime_get_sync() in cti_cpuhp_enable_hw(). It's in CPU hotplug callback with interrupt disabled. Pm_runtime_get_sync() calls clock driver to enable clock which could sleep. Remove pm_runtime_get_sync() in cti_cpuhp_enable_hw() since pm_runtime_get_sync() is called in cti_enabld and pm_runtime_put() is called in cti_disabled. No need to increase pm count when CPU gets online since it's not decreased when CPU is offline.
[ 105.800279] BUG: scheduling while atomic: swapper/1/0/0x00000002 [ 105.800290] Modules linked in: [ 105.800327] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 5.9.0-rc1-gff1304be0a05-dirty #21 [ 105.800337] Hardware name: Thundercomm Dragonboard 845c (DT) [ 105.800353] Call trace: [ 105.800414] dump_backtrace+0x0/0x1d4 [ 105.800439] show_stack+0x14/0x1c [ 105.800462] dump_stack+0xc0/0x100 [ 105.800490] __schedule_bug+0x58/0x74 [ 105.800523] __schedule+0x590/0x65c [ 105.800538] schedule+0x78/0x10c [ 105.800553] schedule_timeout+0x188/0x250 [ 105.800585] qmp_send.constprop.10+0x12c/0x1b0 [ 105.800599] qmp_qdss_clk_prepare+0x18/0x20 [ 105.800622] clk_core_prepare+0x48/0xd4 [ 105.800639] clk_prepare+0x20/0x34 [ 105.800663] amba_pm_runtime_resume+0x54/0x90 [ 105.800695] __rpm_callback+0xdc/0x138 [ 105.800709] rpm_callback+0x24/0x78 [ 105.800724] rpm_resume+0x328/0x47c [ 105.800739] __pm_runtime_resume+0x50/0x74 [ 105.800768] cti_starting_cpu+0x40/0xa4 [ 105.800795] cpuhp_invoke_callback+0x84/0x1e0 [ 105.800814] notify_cpu_starting+0x9c/0xb8 [ 105.800834] secondary_start_kernel+0xd8/0x164 [ 105.800933] CPU1: Booted secondary processor 0x0000000100 [0x517f803c]
Fixes: e9b880581d55 ("coresight: cti: Add CPU Hotplug handling to CTI driver") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org --- drivers/hwtracing/coresight/coresight-cti.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 869569eb8c7f..baba6af83440 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -126,9 +126,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata) { struct cti_config *config = &drvdata->config; - struct device *dev = &drvdata->csdev->dev;
- pm_runtime_get_sync(dev->parent); spin_lock(&drvdata->spinlock); config->hw_powered = true;
@@ -148,7 +146,6 @@ static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata) /* did not re-enable due to no claim / no request */ cti_hp_not_enabled: spin_unlock(&drvdata->spinlock); - pm_runtime_put(dev->parent); }
/* disable hardware */
On Tue, 18 Aug 2020 at 12:11, Tingwei Zhang tingwei@codeaurora.org wrote:
Below BUG is triggered by call pm_runtime_get_sync() in cti_cpuhp_enable_hw(). It's in CPU hotplug callback with interrupt disabled. Pm_runtime_get_sync() calls clock driver to enable clock which could sleep. Remove pm_runtime_get_sync() in cti_cpuhp_enable_hw() since pm_runtime_get_sync() is called in cti_enabld and pm_runtime_put() is called in cti_disabled. No need to increase pm count when CPU gets online since it's not decreased when CPU is offline.
[ 105.800279] BUG: scheduling while atomic: swapper/1/0/0x00000002 [ 105.800290] Modules linked in: [ 105.800327] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 5.9.0-rc1-gff1304be0a05-dirty #21 [ 105.800337] Hardware name: Thundercomm Dragonboard 845c (DT) [ 105.800353] Call trace: [ 105.800414] dump_backtrace+0x0/0x1d4 [ 105.800439] show_stack+0x14/0x1c [ 105.800462] dump_stack+0xc0/0x100 [ 105.800490] __schedule_bug+0x58/0x74 [ 105.800523] __schedule+0x590/0x65c [ 105.800538] schedule+0x78/0x10c [ 105.800553] schedule_timeout+0x188/0x250 [ 105.800585] qmp_send.constprop.10+0x12c/0x1b0 [ 105.800599] qmp_qdss_clk_prepare+0x18/0x20 [ 105.800622] clk_core_prepare+0x48/0xd4 [ 105.800639] clk_prepare+0x20/0x34 [ 105.800663] amba_pm_runtime_resume+0x54/0x90 [ 105.800695] __rpm_callback+0xdc/0x138 [ 105.800709] rpm_callback+0x24/0x78 [ 105.800724] rpm_resume+0x328/0x47c [ 105.800739] __pm_runtime_resume+0x50/0x74 [ 105.800768] cti_starting_cpu+0x40/0xa4 [ 105.800795] cpuhp_invoke_callback+0x84/0x1e0 [ 105.800814] notify_cpu_starting+0x9c/0xb8 [ 105.800834] secondary_start_kernel+0xd8/0x164 [ 105.800933] CPU1: Booted secondary processor 0x0000000100 [0x517f803c]
Fixes: e9b880581d55 ("coresight: cti: Add CPU Hotplug handling to CTI driver") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 869569eb8c7f..baba6af83440 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -126,9 +126,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata) { struct cti_config *config = &drvdata->config;
struct device *dev = &drvdata->csdev->dev;pm_runtime_get_sync(dev->parent); spin_lock(&drvdata->spinlock); config->hw_powered = true;@@ -148,7 +146,6 @@ static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata) /* did not re-enable due to no claim / no request */ cti_hp_not_enabled: spin_unlock(&drvdata->spinlock);
pm_runtime_put(dev->parent);}
/* disable hardware */
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
Reviewed-by Mike Leach mike.leach@linaro.org
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight] [ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI devices") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org --- drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata) CS_LOCK(drvdata->base); }
-static void cti_enable_hw_smp_call(void *info) -{ - struct cti_drvdata *drvdata = info; - - cti_write_all_hw_regs(drvdata); -} - /* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) if (rc) goto cti_err_not_enabled;
- if (drvdata->ctidev.cpu >= 0) { - rc = smp_call_function_single(drvdata->ctidev.cpu, - cti_enable_hw_smp_call, - drvdata, 1); - if (rc) - goto cti_err_not_enabled; - } else { - cti_write_all_hw_regs(drvdata); - } + cti_write_all_hw_regs(drvdata);
config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count);
Hi Tingwei
On Tue, 18 Aug 2020 at 12:11, Tingwei Zhang tingwei@codeaurora.org wrote:
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight] [ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
Agreed.
Reviewed-by Mike Leach mike.leach@linaro.org
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI devices") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata) CS_LOCK(drvdata->base); }
-static void cti_enable_hw_smp_call(void *info) -{
struct cti_drvdata *drvdata = info;cti_write_all_hw_regs(drvdata);-}
/* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) if (rc) goto cti_err_not_enabled;
if (drvdata->ctidev.cpu >= 0) {rc = smp_call_function_single(drvdata->ctidev.cpu,cti_enable_hw_smp_call,drvdata, 1);if (rc)goto cti_err_not_enabled;} else {cti_write_all_hw_regs(drvdata);}
cti_write_all_hw_regs(drvdata); config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count);-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
CoreSight mailing list CoreSight@lists.linaro.org https://lists.linaro.org/mailman/listinfo/coresight
Hi Tingwei,
On Tue, Aug 18, 2020 at 07:10:57PM +0800, Tingwei Zhang wrote:
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight] [ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
Was this the full log or you did cut some of it?
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
From your explanation above it seems that cti_enable_hw() was called from, say
CPUy, to enable the CTI associated to CPUx. CTIx's drvdata->spinlock was taken and smp_call_function_single() called right after. That woke up CPUx and cti_cpu_pm_notify() was executed on CPUx in interrupt context, trying to take CTIx's drvdata->spinlock. That hung CPUx and the kernel got angry. Is my assessment correct?
If so I don't think the fix suggested in this patch will work. The same condition will happen whenever cti_enable_hw() is called on a CPU to enable a CTI that belongs to another CPU and that cti_cpu_pm_notify() is called on latter CPU at the same time.
I think a better solution is to grab the lock in cti_enable_hw() and check the value of ->ctidev.cpu. If not a global CPU, i.e >= 0, then release the lock and call smp_call_function_single(). In cti_enable_hw_smp_call() take the lock again and move forward from there.
I have applied the other two patches in this set so no need to send them again.
Thanks, Mathieu
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI devices") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata) CS_LOCK(drvdata->base); } -static void cti_enable_hw_smp_call(void *info) -{
- struct cti_drvdata *drvdata = info;
- cti_write_all_hw_regs(drvdata);
-}
/* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) if (rc) goto cti_err_not_enabled;
- if (drvdata->ctidev.cpu >= 0) {
rc = smp_call_function_single(drvdata->ctidev.cpu,cti_enable_hw_smp_call,drvdata, 1);if (rc)goto cti_err_not_enabled;- } else {
cti_write_all_hw_regs(drvdata);- }
- cti_write_all_hw_regs(drvdata);
config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
On Fri, Aug 28, 2020 at 02:12:53AM +0800, Mathieu Poirier wrote:
Hi Tingwei,
On Tue, Aug 18, 2020 at 07:10:57PM +0800, Tingwei Zhang wrote:
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight] [ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
Was this the full log or you did cut some of it?
I cut some CPU registers' value since it's too long and not relevant. The Call trace is full.
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
From your explanation above it seems that cti_enable_hw() was called from, say CPUy, to enable the CTI associated to CPUx. CTIx's drvdata->spinlock was taken and smp_call_function_single() called right after. That woke up CPUx and cti_cpu_pm_notify() was executed on CPUx in interrupt context, trying to take CTIx's drvdata->spinlock. That hung CPUx and the kernel got angry. Is my assessment correct?
Most of them is correct. The only difference is CPUx is power on when cti_enable_hw() is called. Otherwise it will goto cti_state_unchanged: and won't call cti_enable_hw_smp_call(). cti_cpu_pm_notify() is called when CPUx tries to suspend instead of resume.
If so I don't think the fix suggested in this patch will work. The same condition will happen whenever cti_enable_hw() is called on a CPU to enable a CTI that belongs to another CPU and that cti_cpu_pm_notify() is called on latter CPU at the same time.
I'm not sure I understand this correctly. Let me clarify it a little bit. It's a deadlock since cti_enable_hw() holds the spinlock and calls cti_enable_hw_smp_call() from CPUx to enable CTI associated to CPUy. It waits for cti_enable_hw_smp_call() to return. IPI is sent to CPUy while CPUy is in cti_cpu_pm_notify() and waits for spinlock. In this patch, I remove cti_enable_hw_smp_call() and write CTI CPU directly on CPUx. It won't wait for CPUy and release spinlock after program registers of CTI. After cti_enable_hw() releases spinlock, cti_cpu_pm_notify() will continue to run. Since spinlock is held and config->hw_powered is true, we don't need to worry about CPUy power down when we program CTI on CPUx.
I think a better solution is to grab the lock in cti_enable_hw() and check the value of ->ctidev.cpu. If not a global CPU, i.e >= 0, then release the lock and call smp_call_function_single(). In cti_enable_hw_smp_call() take the lock again and move forward from there.
After cti_enable_hw() releases the lock, it's possible that CPU is offline by user, cti_enable_hw_smp_call() will fail in this case.
I have applied the other two patches in this set so no need to send them again.
Thanks, Tingwei
Thanks, Mathieu
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI
devices")
Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c
b/drivers/hwtracing/coresight/coresight-cti.c
index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata
*drvdata)
CS_LOCK(drvdata->base); } -static void cti_enable_hw_smp_call(void *info) -{
- struct cti_drvdata *drvdata = info;
- cti_write_all_hw_regs(drvdata);
-}
/* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata
*drvdata)
if (rc) goto cti_err_not_enabled;
- if (drvdata->ctidev.cpu >= 0) {
rc = smp_call_function_single(drvdata->ctidev.cpu,cti_enable_hw_smp_call,drvdata, 1);if (rc)goto cti_err_not_enabled;- } else {
cti_write_all_hw_regs(drvdata);- }
- cti_write_all_hw_regs(drvdata);
config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Fri, Aug 28, 2020 at 11:18:18AM +0800, Tingwei Zhang wrote:
On Fri, Aug 28, 2020 at 02:12:53AM +0800, Mathieu Poirier wrote:
Hi Tingwei,
On Tue, Aug 18, 2020 at 07:10:57PM +0800, Tingwei Zhang wrote:
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight] [ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
Was this the full log or you did cut some of it?
I cut some CPU registers' value since it's too long and not relevant. The Call trace is full.
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
From your explanation above it seems that cti_enable_hw() was called from, say CPUy, to enable the CTI associated to CPUx. CTIx's drvdata->spinlock was taken and smp_call_function_single() called right after. That woke up CPUx and cti_cpu_pm_notify() was executed on CPUx in interrupt context, trying to take CTIx's drvdata->spinlock. That hung CPUx and the kernel got angry. Is my assessment correct?
Most of them is correct. The only difference is CPUx is power on when cti_enable_hw() is called. Otherwise it will goto cti_state_unchanged: and won't call cti_enable_hw_smp_call(). cti_cpu_pm_notify() is called when CPUx tries to suspend instead of resume.
If so I don't think the fix suggested in this patch will work. The same condition will happen whenever cti_enable_hw() is called on a CPU to enable a CTI that belongs to another CPU and that cti_cpu_pm_notify() is called on latter CPU at the same time.
I'm not sure I understand this correctly. Let me clarify it a little bit. It's a deadlock since cti_enable_hw() holds the spinlock and calls cti_enable_hw_smp_call() from CPUx to enable CTI associated to CPUy. It waits for cti_enable_hw_smp_call() to return. IPI is sent to CPUy while CPUy is in cti_cpu_pm_notify() and waits for spinlock. In this patch, I remove cti_enable_hw_smp_call() and write CTI CPU directly on CPUx. It won't wait for CPUy and release spinlock after program registers of CTI. After cti_enable_hw() releases spinlock, cti_cpu_pm_notify() will continue to run. Since spinlock is held and config->hw_powered is true, we don't need to worry about CPUy power down when we program CTI on CPUx.
I think a better solution is to grab the lock in cti_enable_hw() and check the value of ->ctidev.cpu. If not a global CPU, i.e >= 0, then release the lock and call smp_call_function_single(). In cti_enable_hw_smp_call() take the lock again and move forward from there.
After cti_enable_hw() releases the lock, it's possible that CPU is offline by user, cti_enable_hw_smp_call() will fail in this case.
I took another look at your solution and you are correct, CPUy won't lock but rather spin waiting for cti_enable_hw() to finish on CPUx. To make sure CPUx is not interrupted while executing cti_enable_hw() I suggest to use spin_lock_irq().
Thanks, Mathieu
I have applied the other two patches in this set so no need to send them again.
Thanks, Tingwei
Thanks, Mathieu
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI
devices")
Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c
b/drivers/hwtracing/coresight/coresight-cti.c
index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata
*drvdata)
CS_LOCK(drvdata->base); } -static void cti_enable_hw_smp_call(void *info) -{
- struct cti_drvdata *drvdata = info;
- cti_write_all_hw_regs(drvdata);
-}
/* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata
*drvdata)
if (rc) goto cti_err_not_enabled;
- if (drvdata->ctidev.cpu >= 0) {
rc = smp_call_function_single(drvdata->ctidev.cpu,cti_enable_hw_smp_call,drvdata, 1);if (rc)goto cti_err_not_enabled;- } else {
cti_write_all_hw_regs(drvdata);- }
- cti_write_all_hw_regs(drvdata);
config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Tue, Sep 01, 2020 at 04:28:19AM +0800, Mathieu Poirier wrote:
On Fri, Aug 28, 2020 at 11:18:18AM +0800, Tingwei Zhang wrote:
On Fri, Aug 28, 2020 at 02:12:53AM +0800, Mathieu Poirier wrote:
Hi Tingwei,
On Tue, Aug 18, 2020 at 07:10:57PM +0800, Tingwei Zhang wrote:
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128
[coresight]
[ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
Was this the full log or you did cut some of it?
I cut some CPU registers' value since it's too long and not relevant. The Call trace is full.
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
From your explanation above it seems that cti_enable_hw() was called
from,
say CPUy, to enable the CTI associated to CPUx. CTIx's drvdata->spinlock
was
taken and smp_call_function_single() called right after. That woke up CPUx
and
cti_cpu_pm_notify() was executed on CPUx in interrupt context, trying
to
take CTIx's drvdata->spinlock. That hung CPUx and the kernel got angry.
Is my
assessment correct?
Most of them is correct. The only difference is CPUx is power on when cti_enable_hw() is called. Otherwise it will goto cti_state_unchanged: and won't call cti_enable_hw_smp_call(). cti_cpu_pm_notify() is called when CPUx tries to suspend instead of resume.
If so I don't think the fix suggested in this patch will work. The
same
condition will happen whenever cti_enable_hw() is called on a CPU to enable a CTI that belongs to another CPU and that cti_cpu_pm_notify() is called
on
latter CPU at the same time.
I'm not sure I understand this correctly. Let me clarify it a little
bit.
It's a deadlock since cti_enable_hw() holds the spinlock and calls cti_enable_hw_smp_call() from CPUx to enable CTI associated to CPUy. It waits for cti_enable_hw_smp_call() to return. IPI is sent to CPUy while CPUy is in cti_cpu_pm_notify() and waits for spinlock. In this patch, I remove cti_enable_hw_smp_call() and write CTI CPU directly on CPUx. It won't wait for CPUy and release spinlock after program registers of CTI. After cti_enable_hw() releases spinlock, cti_cpu_pm_notify() will continue to run. Since spinlock is held and config->hw_powered is true, we don't need to worry about CPUy power down when we program CTI on
CPUx.
I think a better solution is to grab the lock in cti_enable_hw() and
check
the value of ->ctidev.cpu. If not a global CPU, i.e >= 0, then release
the
lock and call smp_call_function_single(). In cti_enable_hw_smp_call() take the lock again and move forward from there.
After cti_enable_hw() releases the lock, it's possible that CPU is
offline
by user, cti_enable_hw_smp_call() will fail in this case.
I took another look at your solution and you are correct, CPUy won't lock but rather spin waiting for cti_enable_hw() to finish on CPUx. To make sure CPUx is not interrupted while executing cti_enable_hw() I suggest to use spin_lock_irq().
Thanks, Mathieu
Sure. I've sent v2 according to your comments.
I have applied the other two patches in this set so no need to send
them
again.
Thanks, Tingwei
Thanks, Mathieu
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI
devices")
Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c
b/drivers/hwtracing/coresight/coresight-cti.c
index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata
*drvdata)
CS_LOCK(drvdata->base); } -static void cti_enable_hw_smp_call(void *info) -{
- struct cti_drvdata *drvdata = info;
- cti_write_all_hw_regs(drvdata);
-}
/* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata
*drvdata)
if (rc) goto cti_err_not_enabled;
- if (drvdata->ctidev.cpu >= 0) {
rc = smp_call_function_single(drvdata->ctidev.cpu,cti_enable_hw_smp_call,drvdata, 1);if (rc)goto cti_err_not_enabled;- } else {
cti_write_all_hw_regs(drvdata);- }
- cti_write_all_hw_regs(drvdata);
config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project
linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Tue, Aug 18, 2020 at 07:10:57PM +0800, Tingwei Zhang wrote:
Deadlock as below is triggered by one CPU holds drvdata->spinlock and calls cti_enable_hw(). Smp_call_function_single() is called in cti_enable_hw() and tries to let another CPU write CTI registers. That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify() and doesn't response to IPI from smp_call_function_single().
[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L 5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1 [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT) [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--) [ 988.357689] pc : smp_call_function_single+0x158/0x1b8 [ 988.362782] lr : smp_call_function_single+0x124/0x1b8 ... [ 988.451638] Call trace: [ 988.454119] smp_call_function_single+0x158/0x1b8 [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti] [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight] [ 988.469855] coresight_enable+0x1f0/0x364 [coresight] [ 988.474957] enable_source_store+0x5c/0x9c [coresight] [ 988.480140] dev_attr_store+0x14/0x28 [ 988.483839] sysfs_kf_write+0x38/0x4c [ 988.487532] kernfs_fop_write+0x1c0/0x2b0 [ 988.491585] vfs_write+0xfc/0x300 [ 988.494931] ksys_write+0x78/0xe0 [ 988.498283] __arm64_sys_write+0x18/0x20 [ 988.502240] el0_svc_common+0x98/0x160 [ 988.506024] do_el0_svc+0x78/0x80 [ 988.509377] el0_sync_handler+0xd4/0x270 [ 988.513337] el0_sync+0x164/0x180
This change write CTI registers directly in cti_enable_hw(). Config->hw_powered has been checked to be true with spinlock holded. CTI is powered and can be programmed until spinlock is released.
Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI devices") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 17 +---------------- 1 file changed, 1 insertion(+), 16 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 3ccc703dc940..869569eb8c7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,13 +86,6 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata) CS_LOCK(drvdata->base); } -static void cti_enable_hw_smp_call(void *info) -{
- struct cti_drvdata *drvdata = info;
- cti_write_all_hw_regs(drvdata);
-}
/* write regs to hardware and enable */ static int cti_enable_hw(struct cti_drvdata *drvdata) { @@ -112,15 +105,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) if (rc) goto cti_err_not_enabled;
- if (drvdata->ctidev.cpu >= 0) {
rc = smp_call_function_single(drvdata->ctidev.cpu,cti_enable_hw_smp_call,drvdata, 1);if (rc)goto cti_err_not_enabled;- } else {
cti_write_all_hw_regs(drvdata);- }
- cti_write_all_hw_regs(drvdata);
I forgot... Looking at the code in cti_enable_hw() the claim tags are not released in the event that smp_call_function_single() fails. Please address that as part of refactoring the function.
Thanks, Mathieu
config->hw_enabled = true; atomic_inc(&drvdata->config.enable_req_count); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
On Tue, 18 Aug 2020 at 12:11, Tingwei Zhang tingwei@codeaurora.org wrote:
Coresight_claim_device() is called in cti_starting_cpu() only when CTI is enabled while coresight_disclaim_device() is called uncontionally in cti_dying_cpu(). This triggered below WARNING. Only call disclaim device when CTI device is enabled to fix it.
[ 75.989643] WARNING: CPU: 1 PID: 14 at kernel/drivers/hwtracing/coresight/coresight.c:209 coresight_disclaim_device_unlocked+0x10/0x24 [ 75.989697] CPU: 1 PID: 14 Comm: migration/1 Not tainted 5.9.0-rc1-gff1304be0a05-dirty #21 [ 75.989709] Hardware name: Thundercomm Dragonboard 845c (DT) [ 75.989737] pstate: 80c00085 (Nzcv daIf +PAN +UAO BTYPE=--) [ 75.989758] pc : coresight_disclaim_device_unlocked+0x10/0x24 [ 75.989775] lr : coresight_disclaim_device+0x24/0x38 [ 75.989783] sp : ffff800011cd3c90 . [ 75.990018] Call trace: [ 75.990041] coresight_disclaim_device_unlocked+0x10/0x24 [ 75.990066] cti_dying_cpu+0x34/0x4c [ 75.990101] cpuhp_invoke_callback+0x84/0x1e0 [ 75.990121] take_cpu_down+0x90/0xe0 [ 75.990154] multi_cpu_stop+0x134/0x160 [ 75.990171] cpu_stopper_thread+0xb0/0x13c [ 75.990196] smpboot_thread_fn+0x1c4/0x270 [ 75.990222] kthread+0x128/0x154 [ 75.990251] ret_from_fork+0x10/0x18
Fixes: e9b880581d55 ("coresight: cti: Add CPU Hotplug handling to CTI driver") Signed-off-by: Tingwei Zhang tingwei@codeaurora.org
drivers/hwtracing/coresight/coresight-cti.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index 3ccc703dc940..d6fea6efec71 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -742,7 +742,8 @@ static int cti_dying_cpu(unsigned int cpu)
spin_lock(&drvdata->spinlock); drvdata->config.hw_powered = false;
coresight_disclaim_device(drvdata->base);
if (drvdata->config.hw_enabled)coresight_disclaim_device(drvdata->base); spin_unlock(&drvdata->spinlock); return 0;}
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
Reviewed-by: Mike Leach mike.leach@linaro.org
-
Mathieu Poirier -
Mike Leach -
Tingwei Zhang -
Tingwei Zhang