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authorChris Wilson <chris@chris-wilson.co.uk>2017-02-28 09:40:11 +0000
committerIngo Molnar <mingo@kernel.org>2017-03-02 09:00:38 +0100
commit2b232e0c3b3a09f3e33750aa20e314f1b80e5361 (patch)
tree14dbb66a5e79dd4083f79040b208411dcba8a442 /kernel/locking
parente2679aecf1060063b97bf187ba1c61430aab0701 (diff)
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@intel.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: f2a5fec17395 ("locking/ww_mutex: Begin kselftests for ww_mutex") Link: http://lkml.kernel.org/r/20170228094011.2595-1-chris@chris-wilson.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/test-ww_mutex.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index da6c9a34f62f..3eb39c588397 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);