linux-kernel - Re: [PATCH v4 1/4] perf/core: Rework forwarding of {task|cpu}-clock events

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Message-ID: <9eeb2273-9690-8f71-4f3f-595310d53600@amd.com>
Date: Fri, 23 Feb 2024 10:57:22 +0530
From: Ravi Bangoria <ravi.bangoria@....com>
To: Pengfei Xu <pengfei.xu@...el.com>
Cc: peterz@...radead.org, namhyung@...nel.org, eranian@...gle.com,
 acme@...nel.org, mark.rutland@....com, jolsa@...nel.org, irogers@...gle.com,
 bp@...en8.de, kan.liang@...ux.intel.com, adrian.hunter@...el.com,
 maddy@...ux.ibm.com, x86@...nel.org, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org, sandipan.das@....com, ananth.narayan@....com,
 santosh.shukla@....com, lkp@...el.com, Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v4 1/4] perf/core: Rework forwarding of {task|cpu}-clock
 events

Hi Pengfei,

On 20-Feb-24 2:11 PM, Pengfei Xu wrote:
> Hi Ravi Bangoria,
> 
> On 2023-05-04 at 16:30:00 +0530, Ravi Bangoria wrote:
>> Currently, PERF_TYPE_SOFTWARE is treated specially since task-clock and
>> cpu-clock events are interfaced through it but internally gets forwarded
>> to their own pmus.
>>
>> Rework this by overwriting event->attr.type in perf_swevent_init() which
>> will cause perf_init_event() to retry with updated type and event will
>> automatically get forwarded to right pmu. With the change, SW pmu no
>> longer needs to be treated specially and can be included in 'pmu_idr'
>> list.
>>
>> Suggested-by: Peter Zijlstra <peterz@...radead.org>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
>> ---
>>  include/linux/perf_event.h | 10 +++++
>>  kernel/events/core.c       | 77 ++++++++++++++++++++------------------
>>  2 files changed, 51 insertions(+), 36 deletions(-)
> 
> Greeting!
> There is task hung in perf_tp_event_init in v6.8-rc4 in guest.

Thanks for the bug report. I'm able to reproduce it. Will try to spend
more time to rootcause it.

Thanks,
Ravi