From: Qian Cai <cai@lca.pw>
To: mingo@redhat.com
Cc: peterz@infradead.org, will@kernel.org, elver@google.com,
linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH] locking/osq_lock: fix a data race in osq_wait_next
Date: Wed, 22 Jan 2020 11:38:57 -0500 [thread overview]
Message-ID: <20200122163857.4605-1-cai@lca.pw> (raw)
KCSAN complains,
write (marked) to 0xffff941ca3b3be00 of 8 bytes by task 670 on cpu 6:
osq_lock+0x24c/0x340
__mutex_lock+0x277/0xd20
mutex_lock_nested+0x31/0x40
memcg_create_kmem_cache+0x2e/0x190
memcg_kmem_cache_create_func+0x40/0x80
process_one_work+0x54c/0xbe0
worker_thread+0x80/0x650
kthread+0x1e0/0x200
ret_from_fork+0x27/0x50
read to 0xffff941ca3b3be00 of 8 bytes by task 703 on cpu 44:
osq_lock+0x18e/0x340
__mutex_lock+0x277/0xd20
mutex_lock_nested+0x31/0x40
memcg_create_kmem_cache+0x2e/0x190
memcg_kmem_cache_create_func+0x40/0x80
process_one_work+0x54c/0xbe0
worker_thread+0x80/0x650
kthread+0x1e0/0x200
ret_from_fork+0x27/0x50
which points to those lines in osq_wait_next(),
next = xchg(&node->next, NULL);
if (next)
break;
Since only the read is outside of critical sections, fixed it by adding
a READ_ONCE().
Signed-off-by: Qian Cai <cai@lca.pw>
---
kernel/locking/osq_lock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index 6ef600aa0f47..8f565165019a 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -77,7 +77,7 @@ osq_wait_next(struct optimistic_spin_queue *lock,
*/
if (node->next) {
next = xchg(&node->next, NULL);
- if (next)
+ if (READ_ONCE(next))
break;
}
--
2.21.0 (Apple Git-122.2)
next reply other threads:[~2020-01-22 16:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-22 16:38 Qian Cai [this message]
2020-01-22 16:59 ` [PATCH] locking/osq_lock: fix a data race in osq_wait_next Will Deacon
2020-01-22 17:08 ` Qian Cai
2020-01-22 22:38 ` Marco Elver
2020-01-22 23:54 ` Qian Cai
2020-01-23 9:39 ` Peter Zijlstra
2020-01-28 3:11 ` Qian Cai
2020-01-28 11:46 ` Marco Elver
2020-01-28 12:53 ` Qian Cai
2020-01-28 16:52 ` Peter Zijlstra
2020-01-28 16:56 ` Peter Zijlstra
2020-01-29 0:22 ` Paul E. McKenney
2020-01-29 15:29 ` Marco Elver
2020-01-29 18:40 ` Peter Zijlstra
2020-01-30 13:39 ` Marco Elver
2020-01-30 13:48 ` Peter Zijlstra
2020-01-31 3:32 ` Qian Cai
2020-01-29 18:49 ` Peter Zijlstra
2020-01-29 19:26 ` Paul E. McKenney
2020-01-23 9:36 ` Peter Zijlstra
2020-01-28 3:12 ` Qian Cai
2020-01-28 8:18 ` Marco Elver
2020-01-28 10:10 ` Qian Cai
2020-01-28 10:29 ` Marco Elver
2020-01-22 17:09 ` Peter Zijlstra
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