Re: [Qemu-devel] [PATCH v2] block: avoid SIGUSR2

[Stefan Hajnoczi]

On Thu, Oct 27, 2011 at 03:26:23PM +0200, Kevin Wolf wrote:
> Am 19.09.2011 16:37, schrieb Frediano Ziglio:
> > Now that iothread is always compiled sending a signal seems only an
> > additional step. This patch also avoid writing to two pipe (one from signal
> > and one in qemu_service_io).
> > 
> > Work with kvm enabled or disabled. strace output is more readable (less 
> > syscalls).
> > 
> > Signed-off-by: Frediano Ziglio <address@hidden>
> 
> Something in this change has bad effects, in the sense that it seems to
> break bdrv_read_em.

How does it break bdrv_read_em?  Are you seeing QEMU hung with 100% CPU
utilization or deadlocked?

One interesting thing is that qemu_aio_wait() does not release the QEMU
mutex, so we cannot write to a pipe with the mutex held and then spin
waiting for the iothread to do work for us.

Exactly how kill and qemu_notify_event() were different I'm not sure
right now but it could be a factor.

Stefan