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Re: [Qemu-devel] [PATCH] use broadcast on qemu_pause_cond
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] use broadcast on qemu_pause_cond |
Date: |
Mon, 25 Jan 2016 14:18:42 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 |
On 25/01/2016 11:08, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Jiri saw a hang on pause_all_vcpus called from postcopy_start,
> where the cpus are all apparently stopped ('stopped' flag set)
> but pause_all_vcpus is still stuck on a cond_wait on qemu_paused_cond.
> We suspect this is happening if a qmp_stop is called at about the
> same time as the postcopy code calls that pause_all_vcpus;
> although they both should have the main lock held, Paolo spotted
> the cond_wait unlocks the global lock so perhaps they both
> could end up waiting at the same time?
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> Reported-by: Jiri Denemark <address@hidden>
> ---
> cpus.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/cpus.c b/cpus.c
> index 3efff6b..1e97cc4 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -986,7 +986,7 @@ static void qemu_wait_io_event_common(CPUState *cpu)
> if (cpu->stop) {
> cpu->stop = false;
> cpu->stopped = true;
> - qemu_cond_signal(&qemu_pause_cond);
> + qemu_cond_broadcast(&qemu_pause_cond);
> }
> flush_queued_work(cpu);
> cpu->thread_kicked = false;
> @@ -1396,7 +1396,7 @@ void cpu_stop_current(void)
> current_cpu->stop = false;
> current_cpu->stopped = true;
> cpu_exit(current_cpu);
> - qemu_cond_signal(&qemu_pause_cond);
> + qemu_cond_broadcast(&qemu_pause_cond);
> }
> }
>
>
Thanks, queued.
Paolo