From 23722fb46725da42b80bc55a91a9bac69e35188a Mon Sep 17 00:00:00 2001 From: Sudeep Holla Date: Thu, 21 Jul 2022 14:03:29 +0100 Subject: [PATCH] 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 Cc: Suzuki K Poulose Cc: Mike Leach Cc: Leo Yan Signed-off-by: Sudeep Holla Reviewed-by: Mike Leach Signed-off-by: Suzuki K Poulose Link: https://lore.kernel.org/r/20220721130329.3787211-1-sudeep.holla@arm.com --- drivers/hwtracing/coresight/coresight-core.c | 7 ++++--- drivers/hwtracing/coresight/coresight-cti-core.c | 5 +++-- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index d5dbc67bacb44a..f3068175ca9d9e 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 8988b2ed2ea6f5..1be92342b5b98e 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; } }