Tejun, Jan, Jens, Can you review this patch? syzbot has hit this bug for nearly 4000 times but is still unable to find a reproducer. Therefore, the only way to test would be to apply this patch upstream and test whether the problem is solved.
On 2018/04/24 21:19, Tetsuo Handa wrote: >>From 39ed6be8a2c12dfe54feaa5abbc2ec46103022bf Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa <[email protected]> > Date: Tue, 24 Apr 2018 11:59:08 +0900 > Subject: [PATCH] bdi: wake up concurrent wb_shutdown() callers. > > syzbot is reporting hung tasks at wait_on_bit(WB_shutting_down) in > wb_shutdown() [1]. This might be because commit 5318ce7d46866e1d ("bdi: > Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") forgot to call > wake_up_bit(WB_shutting_down) after clear_bit(WB_shutting_down). > > [1] > https://syzkaller.appspot.com/bug?id=b297474817af98d5796bc544e1bb806fc3da0e5e > > Signed-off-by: Tetsuo Handa <[email protected]> > Reported-by: syzbot <[email protected]> > Fixes: 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in > cgwb_bdi_destroy()") > Cc: Tejun Heo <[email protected]> > Cc: Jan Kara <[email protected]> > Cc: Jens Axboe <[email protected]> > --- > mm/backing-dev.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index 023190c..dadac99 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -384,6 +384,8 @@ static void wb_shutdown(struct bdi_writeback *wb) > */ > smp_wmb(); > clear_bit(WB_shutting_down, &wb->state); > + smp_mb(); /* advised by wake_up_bit() */ > + wake_up_bit(&wb->state, WB_shutting_down); > } > > static void wb_exit(struct bdi_writeback *wb) >
