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Re: [Qemu-devel] [PATCH 1/3] block: add BlockBackend->in_flight counter
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 1/3] block: add BlockBackend->in_flight counter |
Date: |
Fri, 9 Feb 2018 18:23:14 +0100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
Am 09.02.2018 um 17:28 hat Paolo Bonzini geschrieben:
> On 08/02/2018 18:18, Stefan Hajnoczi wrote:
> > + BlockDriverState *bs = blk_bs(blk);
> > +
> > + if (bs) {
> > + bdrv_drained_begin(bs);
> > + }
> > +
> > + /* We may have aio requests like -ENOMEDIUM in flight */
> > + while (atomic_mb_read(&blk->in_flight) > 0) {
> > + aio_poll(blk_get_aio_context(blk), true);
> > + }
> > +
> > + if (bs) {
> > + bdrv_drained_end(bs);
>
> This only works if you are in the default AioContext, otherwise you can
> run handlers for one AioContexts in two threads.
Should aio_poll() assert that it's called in the right thread to make
sure we obey the rules?
> bdrv_dec_in_flight uses bdrv_wakeup and BDRV_POLL_WHILE to ensure that
> this doesn't happen, so there would be more code that you have to copy
> into block-backend.c.
Instead of copying, can't we generalise it into a POLL_WHILE(ctx,
wakeup, cond) and make BDRV_POLL_WHILE() a wrapper for that?
Kevin
Re: [Qemu-devel] [PATCH 0/3] block: fix blk_aio_*() segfault when blk->root == NULL, Eric Blake, 2018/02/09