On 06/27/18 16:27, Ming Lei wrote:
On Wed, Jun 27, 2018 at 01:02:12PM -0700, Bart Van Assche wrote:
Because the hctx lock is not held around the only
blk_mq_tag_wakeup_all() call in the block layer, the wait queue
entry removal in blk_mq_dispatch_wake() is protected by the wait
queue lock only. Since the hctx->dispatch_wait entry can occur on
any of the SBQ_WAIT_QUEUES, the wait queue presence check, adding
.dispatch_wait to a wait queue and removing the wait queue entry
must all be protected by both the hctx lock and the wait queue
lock.
Actually we don't need to use hctx->lock for protecting
hctx->dispatch_wait, and one new lock of hctx->dispatch_wait_lock is
enough, please see the following patch:
https://marc.info/?l=linux-block&m=152998658713265&w=2
Then we can avoid to disable irq when acquiring hctx->lock.
I think it's more a matter of taste than a technical decision to choose
which patch goes upstream.
Bart.
