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| author | Kent Overstreet <kent.overstreet@linux.dev> | 2023-11-14 18:52:22 -0500 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2023-11-14 23:44:44 -0500 |
| commit | 61b85cb0d773115d9a4b20c3e67286844cf73f34 (patch) | |
| tree | f7d611b4c3442a847f3461aaa895cafeca113946 | |
| parent | 62d73dfc44d54c97e0df6b947f0bccf6c4b8030e (diff) | |
| download | queue-61b85cb0d773115d9a4b20c3e67286844cf73f34.tar.gz | |
bcachefs: six locks: Fix lost wakeup
In percpu reader mode, trylock() for read had a lost wakeup: on failure
to get the lock, we may have caused a writer to fail to get the lock,
because we temporarily elevated the reader count.
We need to check for waiters after decrementing the read count - not
before.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
| -rw-r--r-- | fs/bcachefs/six.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/fs/bcachefs/six.c b/fs/bcachefs/six.c index b775cf0fb7cbf2..97790445e67ad2 100644 --- a/fs/bcachefs/six.c +++ b/fs/bcachefs/six.c @@ -163,8 +163,11 @@ static int __do_six_trylock(struct six_lock *lock, enum six_lock_type type, this_cpu_sub(*lock->readers, !ret); preempt_enable(); - if (!ret && (old & SIX_LOCK_WAITING_write)) - ret = -1 - SIX_LOCK_write; + if (!ret) { + smp_mb(); + if (atomic_read(&lock->state) & SIX_LOCK_WAITING_write) + ret = -1 - SIX_LOCK_write; + } } else if (type == SIX_LOCK_write && lock->readers) { if (try) { atomic_add(SIX_LOCK_HELD_write, &lock->state); |