linux-kernel - Re: [PATCH] perf: Fix 0 count issue of cpu-clock

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Message-ID: <baf8aceb-5caa-4c3b-80f0-43a4a1449a23@linux.intel.com>
Date: Tue, 18 Nov 2025 19:22:24 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo
 <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Dapeng Mi <dapeng1.mi@...el.com>, Zide Chen <zide.chen@...el.com>,
 Falcon Thomas <thomas.falcon@...el.com>, Xudong Hao <xudong.hao@...el.com>
Subject: Re: [PATCH] perf: Fix 0 count issue of cpu-clock


On 11/18/2025 7:04 PM, Peter Zijlstra wrote:
> On Tue, Nov 18, 2025 at 12:03:09PM +0100, Peter Zijlstra wrote:
>> On Wed, Nov 12, 2025 at 04:05:26PM +0800, Dapeng Mi wrote:
>>
>>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>>> index f6a08c73f783..77d3af5959c1 100644
>>> --- a/kernel/events/core.c
>>> +++ b/kernel/events/core.c
>>> @@ -11964,7 +11964,7 @@ static int cpu_clock_event_add(struct perf_event *event, int flags)
>>>  
>>>  static void cpu_clock_event_del(struct perf_event *event, int flags)
>>>  {
>>> -	cpu_clock_event_stop(event, flags);
>>> +	cpu_clock_event_stop(event, flags | PERF_EF_UPDATE);
>>>  }
>>>  
>>>  static void cpu_clock_event_read(struct perf_event *event)
>>> @@ -12043,7 +12043,7 @@ static int task_clock_event_add(struct perf_event *event, int flags)
>>>  
>>>  static void task_clock_event_del(struct perf_event *event, int flags)
>>>  {
>>> -	task_clock_event_stop(event, PERF_EF_UPDATE);
>>> +	task_clock_event_stop(event, flags | PERF_EF_UPDATE);
>>>  }
>> I think it can both just be: PERF_EF_UPDATE. The only pmu::del() caller
>> hands in flags=0, but if there were to be flags added, we'd have to
>> audit all del methods anyway.
>>
>> Also, the few comments we do have already note that ->del() must do
>> ->stop(EF_UPDATE).
> Updated patch now sits in queue/perf/urgent.

Hi Peter,

Thanks for merging. If we decide not to or the "flags", then the last
sentence "Besides, or flags with PERF_EF_UPDATE for task-clock although
currently the flags argument would always be 0." in the commit message
should be dropped as well. :)

https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=perf/urgent&id=cfaecad27435b4eb6a22bb9d008fec4984e03a21

Thanks,

Dapeng Mi