Re: [PATCH] perf: fix perf_event_context->time

[Song Liu <songliubraving@meta.com>]

> On Mar 2, 2023, at 1:15 PM, Namhyung Kim <namhyung@kernel.org> wrote:
> 
> On Wed, Mar 1, 2023 at 3:16 PM Song Liu <songliubraving@meta.com> wrote:
>> 
>> 
>> 
>>> On Mar 1, 2023, at 2:29 PM, Namhyung Kim <namhyung@kernel.org> wrote:
>>> 
>>> Hi Song,
>>> 
>>> On Tue, Feb 28, 2023 at 11:22 AM Song Liu <song@kernel.org> wrote:
>>>> 
>>>> Time readers rely on perf_event_context->[time|timestamp|timeoffset] to get
>>>> accurate time_enabled and time_running for an event. The difference between
>>>> ctx->timestamp and ctx->time is the among of time when the context is not
>>>> enabled. For cpuctx.ctx, time and timestamp should stay the same, however,
>>> 
>>> I'm not sure if it's correct.  The timestamp can go when the context is disabled
>>> for example, in ctx_resched() even if the NMI watchdog is enabled, right?
>> 
>> I think we do not disable EVENT_TIME for per cpu ctx?
> 
> I can see ctx_sched_out(ctx, EVENT_TIME) in some places.
> Also it'd reset EVENT_TIME if both _PINNED and _FLEXIBLE is
> cleared.

Yeah, you are right. I missed this part. 

Hi Peter, 

Does this fix look good do you?

Thanks,
Song