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coresight: Fix possible deadlock with lock dependency

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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().

Fixes: 177af8285b ("coresight: cti: Enable CTI associated with devices")
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>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220721130329.3787211-1-sudeep.holla@arm.com
This commit is contained in:
Sudeep Holla 2022-07-21 14:03:29 +01:00 committed by Suzuki K Poulose
parent 9abf2313ad
commit 23722fb467
2 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/hwtracing/coresight/coresight-core.c
View File

@ -1687,14 +1687,15 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
ret = coresight_fixup_device_conns(csdev);
if (!ret)
ret = coresight_fixup_orphan_conns(csdev);
if (!ret && cti_assoc_ops && cti_assoc_ops->add)
cti_assoc_ops->add(csdev);
out_unlock:
mutex_unlock(&coresight_mutex);
/* Success */
if (!ret)
if (!ret) {
if (cti_assoc_ops && cti_assoc_ops->add)
cti_assoc_ops->add(csdev);
return csdev;
}
/* Unregister the device if needed */
if (registered) {

5
drivers/hwtracing/coresight/coresight-cti-core.c
View File

@ -541,7 +541,7 @@ cti_match_fixup_csdev(struct cti_device *ctidev, const char *node_name,
/*
* Search the cti list to add an associated CTI into the supplied CS device
* This will set the association if CTI declared before the CS device.
* (called from coresight_register() with coresight_mutex locked).
* (called from coresight_register() without coresight_mutex locked).
*/
static void cti_add_assoc_to_csdev(struct coresight_device *csdev)
{
@ -569,7 +569,8 @@ static void cti_add_assoc_to_csdev(struct coresight_device *csdev)
* if we found a matching csdev then update the ECT
* association pointer for the device with this CTI.
*/
csdev->ect_dev = ect_item->csdev;
coresight_set_assoc_ectdev_mutex(csdev->ect_dev,
ect_item->csdev);
break;
}
}