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@xxxxxxxxxx>
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
