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Re: [Qemu-devel] [PATCH] Revert "blockdev: add note that block_job_cb()
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH] Revert "blockdev: add note that block_job_cb() must be thread-safe" |
Date: |
Wed, 14 Oct 2015 22:51:27 -0400 (EDT) |
----- Original Message -----
> On Tue, Oct 13, 2015 at 06:16:15PM +0800, Fam Zheng wrote:
> > This reverts commit 723c5d93c51bdb3adbc238ce90195c0864aa6cd5.
> >
> > block_job_cb is called by block_job_completed, which is always called in
> > a main loop bottom half in existing block jobs. So we don't need to
> > worry about thread-safety here.
>
> This is not correct. Search for block_job_completed() callers.
>
> For example, block/stream.c has early exit cases that call
> block_job_completed() from the coroutine (i.e. dispatched from a
> coroutine in another AioContext+IOThread).
>
> I think you are assuming that all block_job_completed() callers are
> called from a function scheduled using block_job_defer_to_main_loop().
No, I'm assuming all block_job_completed() callers are (and they should
be) from main thread. Even the early exit cases in stream are so, because
they are in the same thread as stream_start, which is main thread.
>
> Please double-check this.
>
> Thanks,
> Stefan
>
>