Messages in this thread | | | Date | Tue, 19 Sep 2023 18:01:38 +0100 | Subject | Re: [PATCH v2 5/5] hwtracing: hisi_ptt: Add dummy callback pmu::read() | From | Suzuki K Poulose <> |
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On 19/09/2023 14:03, Yicong Yang wrote: > On 2023/9/15 20:53, Suzuki K Poulose wrote: >> On 14/09/2023 12:22, Yicong Yang wrote: >>> From: Junhao He <hejunhao3@huawei.com> >>> >>> When start trace with perf option "-C $cpu" and immediately stop it >>> with SIGTERM or others, the perf core will invoke pmu::read() while >>> the driver doesn't implement it. Add a dummy pmu::read() to avoid >>> any issues. >> >> What issues are we talking about here ? Shouldn't the core perf >> skip the call, if pmu::read() is not available ? >> > > Actually no, the core doesn't check it. So I think that's why some PMUs > like SPE implements a dummy pmu::read() callback. Otherwise we'll > dereference a NULL pointer. > > Currently we only met this on emulated platforms with very slow CPUs, > follow the instructions in the commit above.
Ok, then it calls for a Fixes tag. Please tag it to the commit that introduced the PMU.
Suzuki
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