diff --git a/include/linux/wait_bit.h b/include/linux/wait_bit.h index af0d495430d7..bc96d90bcafd 100644 --- a/include/linux/wait_bit.h +++ b/include/linux/wait_bit.h @@ -259,4 +259,21 @@ int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode) return out_of_line_wait_on_atomic_t(val, action, mode); } +/** + * clear_and_wake_up_bit - clear a bit and wake up anyone waiting on that bit + * + * @bit: the bit of the word being waited on + * @word: the word being waited on, a kernel virtual address + * + * You can use this helper if bitflags are manipulated atomically rather than + * non-atomically under a lock. + */ +static inline void clear_and_wake_up_bit(int bit, void *word) +{ + clear_bit_unlock(bit, word); + /* See wake_up_bit() for which memory barrier you need to use. */ + smp_mb__after_atomic(); + wake_up_bit(word, bit); +} + #endif /* _LINUX_WAIT_BIT_H */ diff --git a/mm/backing-dev.c b/mm/backing-dev.c index e19606bb41a0..dee049a0ec5b 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -381,7 +381,7 @@ static void wb_shutdown(struct bdi_writeback *wb) * the barrier provided by test_and_clear_bit() above. */ smp_wmb(); - clear_bit(WB_shutting_down, &wb->state); + clear_and_wake_up_bit(WB_shutting_down, &wb->state); } static void wb_exit(struct bdi_writeback *wb)