On Wed 13-06-18 09:25:03, Linus Torvalds wrote: > On Wed, Jun 13, 2018 at 9:21 AM Tetsuo Handa > <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > > > > Since multiple addresses share bit_wait_table[256], isn't it possible that > > cgwb_start_shutdown() prematurely returns false due to wake_up_bit() by > > hash-conflicting addresses (i.e. not limited to clear_and_wake_up_bit() from > > wb_shutdown())? I think that we cannot be sure without confirming that > > test_bit(WB_shutting_down, &wb->state) == false after returning from schedule(). > > Right. > > That's _always_ true, btw. Something else entirely could have woken > you up. TASK_UNINTERRUPTIBLE does not mean "nothing else wakes me", it > just means "_signals_ don't wake me". > > So every single sleep always needs to be in a loop. Always. Agreed and in my patch it actually is in a loop - the one iterating the list of active writeback structures. If we get a false wakeup, we find the same structure in the list again and wait again... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
