Commit-ID: 2b232e0c3b3a09f3e33750aa20e314f1b80e5361
Gitweb: http://git.kernel.org/tip/2b232e0c3b3a09f3e33750aa20e314f1b80e5361
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 28 Feb 2017 09:40:11 +0000
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 2 Mar 2017 09:00:38 +0100
locking/ww_mutex: Replace cpu_relax() with cond_resched() for tests
When busy-spinning on a ww_mutex_trylock(), we depend upon the other
thread advancing and releasing the lock. This can not happen on a single
CPU unless we relinquish it:
[ ] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [kworker/0:1:18]
...
[ ] Call Trace:
[ ] mutex_trylock()
[ ] test_mutex_work+0x31/0x56
[ ] process_one_work+0x1b4/0x2f9
[ ] worker_thread+0x1b0/0x27c
[ ] kthread+0xd1/0xd3
[ ] ret_from_fork+0x19/0x30
Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: f2a5fec17395 ("locking/ww_mutex: Begin kselftests for ww_mutex")
Link: http://lkml.kernel.org/r/20170228094011.2595-1-chris@xxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/locking/test-ww_mutex.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index da6c9a3..3eb39c5 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -50,7 +50,7 @@ static void test_mutex_work(struct work_struct *work)
if (mtx->flags & TEST_MTX_TRY) {
while (!ww_mutex_trylock(&mtx->mutex))
- cpu_relax();
+ cond_resched();
} else {
ww_mutex_lock(&mtx->mutex, NULL);
}
@@ -88,7 +88,7 @@ static int __test_mutex(unsigned int flags)
ret = -EINVAL;
break;
}
- cpu_relax();
+ cond_resched();
} while (time_before(jiffies, timeout));
} else {
ret = wait_for_completion_timeout(&mtx.done, TIMEOUT);
--
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