Re: [PATCH 05/11] block: avoid ordered task state change for polled IO
From: jianchao.wang <hidden>
Date: 2018-11-14 02:29:33
Hi Jens On 11/13/18 11:42 PM, Jens Axboe wrote:
quoted hunk ↗ jump to hunk
@@ -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. Thanks Jianchao