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From: Xiaoguang Wang <[email protected]>
To: io-uring <[email protected]>
Cc: "[email protected]" <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Stefano Garzarella <[email protected]>
Subject: Question about patch "io_uring: add submission polling"
Date: Fri, 16 Oct 2020 16:55:45 +0800	[thread overview]
Message-ID: <[email protected]> (raw)

hi,

I have questions about below code comments, which was included in patch
"io_uring: add submission polling",
------------------------------------------------------------
     /*
      * Drop cur_mm before scheduling, we can't hold it for
      * long periods (or over schedule()). Do this before
      * adding ourselves to the waitqueue, as the unuse/drop
      * may sleep.
      */
     if (cur_mm) {
             unuse_mm(cur_mm);
             mmput(cur_mm);
             cur_mm = NULL;
     }

     prepare_to_wait(&ctx->sqo_wait, &wait, TASK_INTERRUPTIBLE);
-------------------------------------------------------------
Stefano submited a patch "io_uring: prevent sq_thread from spinning when it should stop",
I understand what issue Stefano fixed, but don't understand below comments.

Can anyone help to explain why we need to rop cur_mm before scheduling, or
why we can't hold it for long periods (or over schedule()), and if we
unuse/drop mm after adding ourselves to the waitqueue, what issue will
happen when unuse/drop sleeps, thanks.

Regards,
Xiaoguang Wang

             reply	other threads:[~2020-10-16  8:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16  8:55 Xiaoguang Wang [this message]
2020-10-16 13:27 ` Question about patch "io_uring: add submission polling" Jens Axboe
2020-10-19  2:52   ` Xiaoguang Wang

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