On 05/14, Peter Zijlstra wrote: > > On Wed, May 14, 2014 at 06:11:52PM +0200, Oleg Nesterov wrote: > > > > I mean, we do not need mb() before __wake_up(). We need it only because > > __wake_up_bit() checks waitqueue_active(). > > > > > > And at least > > > > fs/cachefiles/namei.c:cachefiles_delete_object() > > fs/block_dev.c:blkdev_get() > > kernel/signal.c:task_clear_jobctl_trapping() > > security/keys/gc.c:key_garbage_collector() > > > > look obviously wrong. > > > > I would be happy to send the fix, but do I need to split it per-file? > > Given that it is trivial, perhaps I can send a single patch? > > Since its all the same issue a single patch would be fine I think. Actually blkdev_get() is fine, it relies on bdev_lock. But bd_prepare_to_claim() is the good example of abusing bit_waitqueue(). Not only it is itself suboptimal, this doesn't allow to optimize wake_up_bit-like paths. And there are more, say, inode_sleep_on_writeback(). Plus we have wait_on_atomic_t() which I think should be generalized or even unified with the regular wait_on_bit(). Perhaps I'll try to do this later, fortunately the recent patch from Neil greatly reduced the number of "action" functions. As for cachefiles_walk_to_object() and key_garbage_collector(), it still seems to me they need smp_mb__after_clear_bit() but I'll leave this to David, I am not comfortable to change the code I absolutely do not understand. In particular, I fail to understand why key_garbage_collector() does smp_mb() before clear_bit(). At least it could be smp_mb__before_clear_bit(). So let me send a trivial patch which only changes task_clear_jobctl_trapping(). Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
