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Date: Fri, 11 Jan 2019 16:14:26 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/6] block: Acquire the AioContext in
 scsi_*_realize()
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To: Alberto Garcia <berto@igalia.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Max Reitz <mreitz@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

Am 11.01.2019 um 16:05 hat Alberto Garcia geschrieben:
> On Fri 11 Jan 2019 04:02:13 PM CET, Kevin Wolf wrote:
> >> @@ -2568,7 +2579,10 @@ static void scsi_block_realize(SCSIDevice *dev, Error **errp)
> >>      }
> >>  
> >>      /* check we are using a driver managing SG_IO (version 3 and after) */
> >> +    ctx = blk_get_aio_context(s->qdev.conf.blk);
> >> +    aio_context_acquire(ctx);
> >>      rc = blk_ioctl(s->qdev.conf.blk, SG_GET_VERSION_NUM, &sg_version);
> >> +    aio_context_release(ctx);
> >>      if (rc < 0) {
> >>          error_setg_errno(errp, -rc, "cannot get SG_IO version number");
> >>          if (rc != -EPERM) {
> >
> > This is probably not enough. get_device_type() and
> > scsi_generic_read_device_inquiry() below issue more ioctls (but we
> > need to be careful not to include the scsi_realize() call in the
> > locked section if you take the lock again there).
> 
> Hmmm, another alternative is not to take the lock in scsi_realize() and
> take it instead in all the functions that call it (it's 4 or 5).

We touch most of them anyway, so I think it is an option.

Kevin