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Re: [PATCH] replay: synchronize on every virtual timer callback
From: |
Paolo Bonzini |
Subject: |
Re: [PATCH] replay: synchronize on every virtual timer callback |
Date: |
Thu, 21 May 2020 15:22:40 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 06/05/20 10:17, Pavel Dovgalyuk wrote:
> Sometimes virtual timer callbacks depend on order
> of virtual timer processing and warping of virtual clock.
> Therefore every callback should be logged to make replay deterministic.
> This patch creates a checkpoint before every virtual timer callback.
> With these checkpoints virtual timers processing and clock warping
> events order is completely deterministic.
>
> Signed-off-by: Pavel Dovgalyuk <address@hidden>
> ---
> util/qemu-timer.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/util/qemu-timer.c b/util/qemu-timer.c
> index d548d3c1ad..47833f338f 100644
> --- a/util/qemu-timer.c
> +++ b/util/qemu-timer.c
> @@ -588,6 +588,11 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
> qemu_mutex_lock(&timer_list->active_timers_lock);
>
> progress = true;
> + /*
> + * Callback may insert new checkpoints, therefore add new checkpoint
> + * for the virtual timers.
> + */
> + need_replay_checkpoint = timer_list->clock->type ==
> QEMU_CLOCK_VIRTUAL;
You need to check replay_mode != REPLAY_MODE_NONE, either here or in the
"if (need_replay_checkpoint)" above. If you choose the latter, you can
remove the other "if (replay_mode != REPLAY_MODE_NONE)".
Also, there is a comment that says that checkpointing "must only be done
once since the clock value stays the same". Is that actually a "can"
rather than a "must"? Should the central replay logic have something
like a checkpoint count, that prevents adding back-to-back equal
checkpoints?
Thanks,
Paolo
> }
> qemu_mutex_unlock(&timer_list->active_timers_lock);
>
>
- Re: [PATCH] replay: synchronize on every virtual timer callback, (continued)
- Re: [PATCH] replay: synchronize on every virtual timer callback, Alex Bennée, 2020/05/18
- Re: [PATCH] replay: synchronize on every virtual timer callback, Pavel Dovgalyuk, 2020/05/19
- Re: [PATCH] replay: synchronize on every virtual timer callback, Alex Bennée, 2020/05/19
- Re: [PATCH] replay: synchronize on every virtual timer callback, Pavel Dovgalyuk, 2020/05/19
- Re: [PATCH] replay: synchronize on every virtual timer callback, Alex Bennée, 2020/05/19
- Re: [PATCH] replay: synchronize on every virtual timer callback, Pavel Dovgalyuk, 2020/05/19
- Re: [PATCH] replay: synchronize on every virtual timer callback, Philippe Mathieu-Daudé, 2020/05/19
- Re: [PATCH] replay: synchronize on every virtual timer callback, Pavel Dovgalyuk, 2020/05/20
- Re: [PATCH] replay: synchronize on every virtual timer callback, Philippe Mathieu-Daudé, 2020/05/20
- Re: [PATCH] replay: synchronize on every virtual timer callback, Pavel Dovgalyuk, 2020/05/20
Re: [PATCH] replay: synchronize on every virtual timer callback,
Paolo Bonzini <=