Commit-ID: 2b232e0c3b3a09f3e33750aa20e314f1b80e5361 Gitweb: http://git.kernel.org/tip/2b232e0c3b3a09f3e33750aa20e314f1b80e5361 Author: Chris Wilson <[email protected]> AuthorDate: Tue, 28 Feb 2017 09:40:11 +0000 Committer: Ingo Molnar <[email protected]> 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 <[email protected]> Signed-off-by: Chris Wilson <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Fixes: f2a5fec17395 ("locking/ww_mutex: Begin kselftests for ww_mutex") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- 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);
