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authorSudeep Holla <sudeep.holla@arm.com>2022-07-21 14:03:29 +0100
committerSuzuki K Poulose <suzuki.poulose@arm.com>2022-10-20 22:32:02 +0100
commit23722fb46725da42b80bc55a91a9bac69e35188a (patch)
tree151b32d97106a5161fa88165db607ad184614b70 /drivers/hwtracing
parent9abf2313adc1ca1b6180c508c25f22f9395cc780 (diff)
downloadlinux-23722fb46725da42b80bc55a91a9bac69e35188a.tar.bz2
coresight: Fix possible deadlock with lock dependency
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: 177af8285b59 ("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
Diffstat (limited to 'drivers/hwtracing')
-rw-r--r--drivers/hwtracing/coresight/coresight-core.c7
-rw-r--r--drivers/hwtracing/coresight/coresight-cti-core.c5
2 files changed, 7 insertions, 5 deletions
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index d5dbc67bacb4..f3068175ca9d 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -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) {
diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
index 8988b2ed2ea6..1be92342b5b9 100644
--- a/drivers/hwtracing/coresight/coresight-cti-core.c
+++ b/drivers/hwtracing/coresight/coresight-cti-core.c
@@ -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;
}
}