On 11/13/18 7:29 PM, jianchao.wang wrote: > Hi Jens > > On 11/13/18 11:42 PM, Jens Axboe wrote: >> @@ -181,6 +181,7 @@ static void blkdev_bio_end_io_simple(struct bio *bio) >> struct task_struct *waiter = bio->bi_private; >> >> WRITE_ONCE(bio->bi_private, NULL); >> + smp_wmb(); >> wake_up_process(waiter); >> } > > > The wake up path has contained a full memory barrier with the raw_spin_lock > and following smp_mb__after_spinlock > > Please refer to: > > wake_up_process > -> try_to_wake_up > > raw_spin_lock_irqsave(&p->pi_lock, flags); > smp_mb__after_spinlock(); > > So the smp_wmb here is not necessary. And I guess we don't need it for the next patch either, since the path that doesn't take wake_up_process() is local. I'll update them (again), thanks! -- Jens Axboe
