[PATCH v2 4/7] blk-mq: Introduce blk_quiesce_queue() and blk_resume_queue()
tom.leiming at gmail.com
Wed Oct 5 09:11:31 PDT 2016
On Wed, Oct 5, 2016 at 10:46 PM, Bart Van Assche
<bart.vanassche at sandisk.com> wrote:
> On 10/04/16 21:32, Ming Lei wrote:
>> On Wed, Oct 5, 2016 at 12:16 PM, Bart Van Assche
>> <bart.vanassche at sandisk.com> wrote:
>>> On 10/01/16 15:56, Ming Lei wrote:
>>>> If we just call the rcu/srcu read lock(or the mutex) around .queue_rq(),
>>>> the above code needn't to be duplicated any more.
>>> Can you have a look at the attached patch? That patch uses an srcu read
>>> for all queue types, whether or not the BLK_MQ_F_BLOCKING flag has been
>> That is much cleaner now.
>>> Additionally, I have dropped the QUEUE_FLAG_QUIESCING flag. Just like
>>> previous versions, this patch has been tested.
>> I think the flag of QUEUE_FLAG_QUIESCING is still needed because we
>> have to set this flag to prevent new coming .queue_rq() from being run,
>> and synchronize_srcu() won't wait for completion of that at all (see
>> section of 'Update-Side Primitives' in ).
>>  https://lwn.net/Articles/202847/
> Hello Ming,
> How about using the existing flag BLK_MQ_S_STOPPED instead of introducing a
> new QUEUE_FLAG_QUIESCING flag? From the comment above blk_mq_quiesce_queue()
That looks fine, and we need to stop direct issue first after hw queue
> in the patch that was attached to my previous e-mail: "Additionally, it is
> not prevented that new queue_rq() calls occur unless the queue has been
> stopped first."
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