Re: [Qemu-devel] [PATCH 1/4] iothread: replace init_done_cond with a semaphore

[Peter Xu]

On Fri, Feb 22, 2019 at 07:25:16AM +0100, Marc-André Lureau wrote:
> Hi
> 
> On Fri, Feb 22, 2019 at 4:14 AM Peter Xu <address@hidden> wrote:
> >
> > Only sending an init-done message using lock+cond seems an overkill to
> > me.  Replacing it with a simpler semaphore.
> >
> > Meanwhile, init the semaphore unconditionally, then we can destroy it
> > unconditionally too in finalize which seems cleaner.
> >
> > Signed-off-by: Peter Xu <address@hidden>
> 
> The lock is also protecting thread_id.

IMHO it's fine because thread_id is only changed at the beginning of
iothread_run where the caller will definitely wait for the thread_id
to be generated.  Here qemu_sem_post() should at least contain one
write memory barrier there to make sure the waker will read the
correct value after sem_wait() and then later on thread_id is never
changed.

Regards,

-- 
Peter Xu