From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Yicong Yang <yangyicong@huawei.com>,
mathieu.poirier@linaro.org, jonathan.cameron@huawei.com,
linux-kernel@vger.kernel.org
Cc: yangyicong@hisilicon.com, alexander.shishkin@linux.intel.com,
helgaas@kernel.org, linux-pci@vger.kernel.org,
prime.zeng@hisilicon.com, linuxarm@huawei.com,
hejunhao3@huawei.com
Subject: Re: [PATCH v2 5/5] hwtracing: hisi_ptt: Add dummy callback pmu::read()
Date: Tue, 19 Sep 2023 18:01:38 +0100 [thread overview]
Message-ID: <3cc013bd-c85e-b28a-f921-d5593b3935a4@arm.com> (raw)
In-Reply-To: <75b93d15-f099-5d17-caa9-94b0390773cf@huawei.com>
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
next prev parent reply other threads:[~2023-09-19 17:01 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-14 11:22 [PATCH v2 0/5] Several updates for PTT driver Yicong Yang
2023-09-14 11:22 ` [PATCH v2 1/5] hwtracing: hisi_ptt: Disable interrupt after trace end Yicong Yang
2023-09-14 11:22 ` [PATCH v2 2/5] hwtracing: hisi_ptt: Handle the interrupt in hardirq context Yicong Yang
2023-09-14 11:22 ` [PATCH v2 3/5] hwtracing: hisi_ptt: Optimize the trace data committing Yicong Yang
2023-09-15 14:44 ` Suzuki K Poulose
2023-09-19 13:19 ` Yicong Yang
2023-09-14 11:22 ` [PATCH v2 4/5] hwtracing: hisi_ptt: Don't try to attach a task Yicong Yang
2023-09-14 11:22 ` [PATCH v2 5/5] hwtracing: hisi_ptt: Add dummy callback pmu::read() Yicong Yang
2023-09-15 12:53 ` Suzuki K Poulose
2023-09-19 13:03 ` Yicong Yang
2023-09-19 17:01 ` Suzuki K Poulose [this message]
2023-09-20 7:10 ` Yicong Yang
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