The "lock_page_killable()" function waits for exclusive access to the page lock bit using the WQ_FLAG_EXCLUSIVE bit in the waitqueue entry set. That means that if it gets woken up, other waiters may have been skipped. That, in turn, means that if it sees the page being unlocked, it *must* take that lock and return success, even if a lethal signal is also pending. So instead of checking for lethal signals first, we need to check for them after we've checked the actual bit that we were waiting for. Even if that might then delay the killing of the process. This matches the order of the old "wait_on_bit_lock()" infrastructure that the page locking used to use (and is still used in a few other areas). Note that if we still return an error after having unsuccessfully tried to acquire the page lock, that is ok: that means that some other thread was able to get ahead of us and lock the page, and when that other thread then unlocks the page, the wakeup event will be repeated. So any other pending waiters will now get properly woken up.
Unified · Split
| @@ -986,10 +986,6 @@ static inline int wait_on_page_bit_common(wait_queue_head_t *q, · 985 unmodified lines | ||
| 986 | 986 | |
| 987 | 987 | if (likely(test_bit(bit_nr, &page->flags))) { |
| 988 | 988 | io_schedule(); |
| 989 | − if (unlikely(signal_pending_state(state, current))) { | |
| 990 | − ret = -EINTR; | |
| 991 | − break; | |
| 992 | − } | |
| 993 | 989 | } |
| 994 | 990 | |
| 995 | 991 | if (lock) { |
| @@ -999,6 +995,11 @@ static inline int wait_on_page_bit_common(wait_queue_head_t *q, · 3 unmodified lines | ||
| 999 | 995 | if (!test_bit(bit_nr, &page->flags)) |
| 1000 | 996 | break; |
| 1001 | 997 | } |
| 998 | + | |
| 999 | + if (unlikely(signal_pending_state(state, current))) { | |
| 1000 | + ret = -EINTR; | |
| 1001 | + break; | |
| 1002 | + } | |
| 1002 | 1003 | } |
| 1003 | 1004 | |
| 1004 | 1005 | finish_wait(q, wait); |