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six locks: be more careful about lost wakeups

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This is a workaround for a lost wakeup bug we've been seeing - we still
need to discover the actual bug.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet
2023-03-06 07:57:51 -05:00
parent 2640faeb17
commit 4b5b13da52
1 changed files with 11 additions and 3 deletions
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14
fs/bcachefs/six.c
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@@ -142,8 +142,17 @@ static int __do_six_trylock_type(struct six_lock *lock,
* lock, issue a wakeup because we might have caused a
* spurious trylock failure:
*/
#if 0
/*
* This code should be sufficient, but we're seeing unexplained
* lost wakeups:
*/
if (old.write_locking)
ret = -1 - SIX_LOCK_write;
#else
if (!ret)
ret = -1 - SIX_LOCK_write;
#endif
} else if (type == SIX_LOCK_write && lock->readers) {
if (try) {
atomic64_add(__SIX_VAL(write_locking, 1),
@@ -319,11 +328,10 @@ static bool __six_relock_type(struct six_lock *lock, enum six_lock_type type,
* Similar to the lock path, we may have caused a spurious write
* lock fail and need to issue a wakeup:
*/
if (old.write_locking)
six_lock_wakeup(lock, old, SIX_LOCK_write);
if (ret)
six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);
else
six_lock_wakeup(lock, old, SIX_LOCK_write);
return ret;
}