[Qemu-devel] [PATCH v2] qtest: Fix deadloop by running main loop AIO context's timers

[Qemu-devel] [PATCH v2] 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>

---
v2: Only run QEMU_CLOCK_VIRTUAL events. (Paolo).
---
 cpus.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cpus.c b/cpus.c
index 3a5323b..9b3db0b 100644
--- a/cpus.c
+++ b/cpus.c
@@ -378,15 +378,19 @@ static void icount_warp_rt(void *opaque)
 void qtest_clock_warp(int64_t dest)
 {
     int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    AioContext *aio_context;
     assert(qtest_enabled());
+    aio_context = qemu_get_aio_context();
     while (clock < dest) {
         int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL);
         int64_t warp = qemu_soonest_timeout(dest - clock, deadline);
+
         seqlock_write_lock(&timers_state.vm_clock_seqlock);
         timers_state.qemu_icount_bias += warp;
         seqlock_write_unlock(&timers_state.vm_clock_seqlock);
 
         qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
+        timerlist_run_timers(aio_context->tlg.tl[QEMU_CLOCK_VIRTUAL]);
         clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     }
     qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
-- 
1.9.3

Re: [Qemu-devel] [PATCH v2] qtest: Fix deadloop by running main loop AIO context's timers

[Paolo Bonzini]

On 19/01/2015 10:51, 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>
> 
> ---
> v2: Only run QEMU_CLOCK_VIRTUAL events. (Paolo).
> ---
>  cpus.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/cpus.c b/cpus.c
> index 3a5323b..9b3db0b 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -378,15 +378,19 @@ static void icount_warp_rt(void *opaque)
>  void qtest_clock_warp(int64_t dest)
>  {
>      int64_t clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +    AioContext *aio_context;
>      assert(qtest_enabled());
> +    aio_context = qemu_get_aio_context();
>      while (clock < dest) {
>          int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL);
>          int64_t warp = qemu_soonest_timeout(dest - clock, deadline);
> +
>          seqlock_write_lock(&timers_state.vm_clock_seqlock);
>          timers_state.qemu_icount_bias += warp;
>          seqlock_write_unlock(&timers_state.vm_clock_seqlock);
>  
>          qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
> +        timerlist_run_timers(aio_context->tlg.tl[QEMU_CLOCK_VIRTUAL]);
>          clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>      }
>      qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
> 

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Kevin/Stefan, can you apply it to the block branch together with Fam's
qemu-iotests patches for throttling?

Paolo

Re: [Qemu-devel] [PATCH v2] qtest: Fix deadloop by running main loop AIO context's timers

[Stefan Hajnoczi]

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On Mon, Jan 19, 2015 at 05:51:43PM +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>
> 
> ---
> v2: Only run QEMU_CLOCK_VIRTUAL events. (Paolo).
> ---
>  cpus.c | 4 ++++
>  1 file changed, 4 insertions(+)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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