On Tue, Sep 01, 2020 at 02:33:09PM +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 | 24 +++++---------------- 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c index c4e9cc7034ab..d04181c12a7f 100644 --- a/drivers/hwtracing/coresight/coresight-cti.c +++ b/drivers/hwtracing/coresight/coresight-cti.c @@ -86,22 +86,16 @@ 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) { struct cti_config *config = &drvdata->config; struct device *dev = &drvdata->csdev->dev; int rc = 0;

• unsigned long flags;

I have moved this line before "int rc = 0;" and applied your patch.

Thanks, Mathieu

pm_runtime_get_sync(dev->parent);

• spin_lock(&drvdata->spinlock);

• spin_lock_irqsave(&drvdata->spinlock, flags);

/* no need to do anything if enabled or unpowered*/ if (config->hw_enabled || !config->hw_powered) @@ -112,19 +106,11 @@ 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);

• spin_unlock(&drvdata->spinlock);

• spin_unlock_irqrestore(&drvdata->spinlock, flags); return rc;

cti_state_unchanged: @@ -132,7 +118,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata) /* cannot enable due to error */ cti_err_not_enabled:

• spin_unlock(&drvdata->spinlock);

• spin_unlock_irqrestore(&drvdata->spinlock, flags); pm_runtime_put(dev->parent); return rc;

}

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