[Qemu-devel] [PATCH] qtest: Fix deadloop by running main loop AIO context's timers

[Qemu-devel] [PATCH] qtest: Fix deadloop by running main loop AIO context's timers

[Fam Zheng]

qemu_clock_run_timers() only takes care of main_loop_tlg, we shouldn't
forget aio timer list groups.

Currently, the qemu_clock_deadline_ns_all (a few lines above) counts all
the timergroups of this clock type, including aio tlg, but we don't fire
them, so they are never cleared, which makes a dead loop.

For example, this function hangs when trying to drive throttled block
request queue with qtest clock_step.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 cpus.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/cpus.c b/cpus.c
index 3a5323b..dd7e595 100644
--- a/cpus.c
+++ b/cpus.c
@@ -387,6 +387,7 @@ void qtest_clock_warp(int64_t dest)
         seqlock_write_unlock(&timers_state.vm_clock_seqlock);
 
         qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
+        timerlistgroup_run_timers(&qemu_get_aio_context()->tlg);
         clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     }
     qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
-- 
1.9.3

Re: [Qemu-devel] [PATCH] qtest: Fix deadloop by running main loop AIO context's timers

[Stefan Hajnoczi]

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On Fri, Jan 16, 2015 at 04:01:17PM +0800, Fam Zheng wrote:
> qemu_clock_run_timers() only takes care of main_loop_tlg, we shouldn't
> forget aio timer list groups.
> 
> Currently, the qemu_clock_deadline_ns_all (a few lines above) counts all
> the timergroups of this clock type, including aio tlg, but we don't fire
> them, so they are never cleared, which makes a dead loop.
> 
> For example, this function hangs when trying to drive throttled block
> request queue with qtest clock_step.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  cpus.c | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [PATCH] qtest: Fix deadloop by running main loop AIO context's timers

[Paolo Bonzini]

On 16/01/2015 09:01, Fam Zheng wrote:
> qemu_clock_run_timers() only takes care of main_loop_tlg, we shouldn't
> forget aio timer list groups.
> 
> Currently, the qemu_clock_deadline_ns_all (a few lines above) counts all
> the timergroups of this clock type, including aio tlg, but we don't fire
> them, so they are never cleared, which makes a dead loop.
> 
> For example, this function hangs when trying to drive throttled block
> request queue with qtest clock_step.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  cpus.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/cpus.c b/cpus.c
> index 3a5323b..dd7e595 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -387,6 +387,7 @@ void qtest_clock_warp(int64_t dest)
>          seqlock_write_unlock(&timers_state.vm_clock_seqlock);
>  
>          qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
> +        timerlistgroup_run_timers(&qemu_get_aio_context()->tlg);

Good catch.  However, I think it's enough to run the QEMU_CLOCK_VIRTUAL
events, using timerlist_run_timers.

Thanks,

Paolo

>          clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>      }
>      qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
> 

Re: [Qemu-devel] [PATCH] qtest: Fix deadloop by running main loop AIO context's timers

[Fam Zheng]

On Mon, 01/19 10:29, Paolo Bonzini wrote:
> 
> 
> On 16/01/2015 09:01, Fam Zheng wrote:
> > qemu_clock_run_timers() only takes care of main_loop_tlg, we shouldn't
> > forget aio timer list groups.
> > 
> > Currently, the qemu_clock_deadline_ns_all (a few lines above) counts all
> > the timergroups of this clock type, including aio tlg, but we don't fire
> > them, so they are never cleared, which makes a dead loop.
> > 
> > For example, this function hangs when trying to drive throttled block
> > request queue with qtest clock_step.
> > 
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> >  cpus.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/cpus.c b/cpus.c
> > index 3a5323b..dd7e595 100644
> > --- a/cpus.c
> > +++ b/cpus.c
> > @@ -387,6 +387,7 @@ void qtest_clock_warp(int64_t dest)
> >          seqlock_write_unlock(&timers_state.vm_clock_seqlock);
> >  
> >          qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
> > +        timerlistgroup_run_timers(&qemu_get_aio_context()->tlg);
> 
> Good catch.  However, I think it's enough to run the QEMU_CLOCK_VIRTUAL
> events, using timerlist_run_timers.

OK, will fix!

Fam