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| author | Peter Zijlstra <peterz@infradead.org> | 2021-11-29 18:46:46 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-12-04 10:56:23 +0100 |
| commit | 02ea9fc96fe976e7f7e067f38b12202f126e3f2f (patch) | |
| tree | 4df904db607e5635e6f947b2b34cf5067e6d9885 | |
| parent | e08f343be00c3fe8f9f6ac58085c81bcdd231fab (diff) | |
| download | linux-02ea9fc96fe976e7f7e067f38b12202f126e3f2f.tar.gz linux-02ea9fc96fe976e7f7e067f38b12202f126e3f2f.tar.bz2 linux-02ea9fc96fe976e7f7e067f38b12202f126e3f2f.zip | |
locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.
Similar to the issues in commits:
6467822b8cc9 ("locking/rtmutex: Prevent spurious EDEADLK return caused by ww_mutexes")
a055fcc132d4 ("locking/rtmutex: Return success on deadlock for ww_mutex waiters")
ww_rt_mutex_lock() should not return EDEADLK without first going through
the __ww_mutex logic to set the required state. In fact, the chain-walk
can deal with the spurious cycles (per the above commits) this check
warns about and is trying to avoid.
Therefore ignore this test for ww_rt_mutex and simply let things fall
in place.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-4-bigeasy@linutronix.de
| -rw-r--r-- | kernel/locking/rtmutex.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 0c6a48dfcecb..f89620852774 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1103,8 +1103,11 @@ static int __sched task_blocks_on_rt_mutex(struct rt_mutex_base *lock, * the other will detect the deadlock and return -EDEADLOCK, * which is wrong, as the other waiter is not in a deadlock * situation. + * + * Except for ww_mutex, in that case the chain walk must already deal + * with spurious cycles, see the comments at [3] and [6]. */ - if (owner == task) + if (owner == task && !(build_ww_mutex() && ww_ctx)) return -EDEADLK; raw_spin_lock(&task->pi_lock); |