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Date: Wed, 09 Oct 2013 20:03:54 +0200
From: Hans de Goede <hdegoede@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] main-loop: Don't lock starve io-threads
 when main_loop_tlg has pending events
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To: Alex Bligh <alex@alex.org.uk>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org

Hi,

On 10/09/2013 03:18 PM, Alex Bligh wrote:

<snip>

>> qemu_mod_timer(timer->timer, qemu_get_clock_ms(rt_clock) + ms);
>
> qemu_mod_timer does not exist in master.
>
> This line is now:
>
>      timer_mod(timer->timer, qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + ms);

Ah yes my bad, I was accidentally looking at a stable-1.5 checkout.

> This suggests to me either timer->scale is not set to 1000000 (i.e.
> it isn't in milliseconds),

The timer always gets created like this:

     timer->timer = timer_new_ms(QEMU_CLOCK_REALTIME, func, opaque);

> OR ms is zero/negative.

Nope I've added a debug printf to the spice timer code and it all works
as expected.

So I started looking for suspecious timers under audio/*.c and immediately
found this in audio/audio.c :

static void audio_reset_timer (AudioState *s)
{
     if (audio_is_timer_needed ()) {
         timer_mod (s->ts, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + 1);
     }
     else {
         timer_del (s->ts);
     }
}

static void audio_timer (void *opaque)
{
     audio_run ("timer");
     audio_reset_timer (opaque);
}

Note how that is using a timer which expires every freaking nano second,
I think it is very likely that is the culprit.

Regards,

Hans