On 21/07/2022 14:03, Sudeep Holla wrote:

With lockdeps enabled, we get the following warning:

====================================================== WARNING: possible circular locking dependency detected

---

kworker/u12:1/53 is trying to acquire lock: ffff80000adce220 (coresight_mutex){+.+.}-{4:4}, at: coresight_set_assoc_ectdev_mutex+0x3c/0x5c but task is already holding lock: ffff80000add1f60 (ect_mutex){+.+.}-{4:4}, at: cti_probe+0x318/0x394

which lock already depends on the new lock. the existing dependency chain (in reverse order) is:

-> #1 (ect_mutex){+.+.}-{4:4}: __mutex_lock_common+0xd8/0xe60 mutex_lock_nested+0x44/0x50 cti_add_assoc_to_csdev+0x4c/0x184 coresight_register+0x2f0/0x314 tmc_probe+0x33c/0x414

-> #0 (coresight_mutex){+.+.}-{4:4}: __lock_acquire+0x1a20/0x32d0 lock_acquire+0x160/0x308 __mutex_lock_common+0xd8/0xe60 mutex_lock_nested+0x44/0x50 coresight_set_assoc_ectdev_mutex+0x3c/0x5c cti_update_conn_xrefs+0x6c/0xf8 cti_probe+0x33c/0x394

other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ect_mutex); lock(coresight_mutex); lock(ect_mutex); lock(coresight_mutex); *** DEADLOCK ***

4 locks held by kworker/u12:1/53: #0: ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1fc/0x63c #1: (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x228/0x63c #2: (&dev->mutex){....}-{4:4}, at: __device_attach+0x48/0x1a8 #3: (ect_mutex){+.+.}-{4:4}, at: cti_probe+0x318/0x394

To fix the same, call cti_add_assoc_to_csdev without the holding coresight_mutex and confine the locking while setting the associated ect / cti device using coresight_set_assoc_ectdev_mutex().

Cc: Mathieu Poirier mathieu.poirier@linaro.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Cc: Mike Leach mike.leach@linaro.org Cc: Leo Yan leo.yan@linaro.org Signed-off-by: Sudeep Holla sudeep.holla@arm.com

Thanks for the fix. I will push this out at rc1 as fixes.

Thanks Suzuki