From: Stephane Eranian <eranian@google.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Andi Kleen <ak@linux.intel.com>,
kirill.shutemov@linux.intel.com,
Michael Ellerman <mpe@ellerman.id.au>,
benh@kernel.crashing.org, Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH V8 1/4] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE
Date: Wed, 30 Sep 2020 10:17:41 -0700 [thread overview]
Message-ID: <CABPqkBTk6H0Wku8gGJeBD2naFU=WOqp42VSjFBhk_1Wy6bRzXQ@mail.gmail.com> (raw)
In-Reply-To: <35e875ba-2c04-8452-5105-ccacf72840d8@intel.com>
On Wed, Sep 30, 2020 at 7:48 AM Dave Hansen <dave.hansen@intel.com> wrote:
>
> On 9/30/20 7:42 AM, Liang, Kan wrote:
> >> When I tested on my kernel, it panicked because I suspect
> >> current->active_mm could be NULL. Adding a check for NULL avoided the
> >> problem. But I suspect this is not the correct solution.
> >
> > I guess the NULL active_mm should be a rare case. If so, I think it's
> > not bad to add a check and return 0 page size.
>
> I think it would be best to understand why ->active_mm is NULL instead
> of just papering over the problem. If it is papered over, and this is
> common, you might end up effectively turning off your shiny new feature
> inadvertently.
I tried that on a backport of the patch to an older kernel. Maybe the
behavior of active_mm has change compared to tip.git.
I will try again with tip.git.
next prev parent reply other threads:[~2020-09-30 17:17 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 15:26 [PATCH V8 0/4] Add the page size in the perf record (kernel) kan.liang
2020-09-21 15:26 ` [PATCH V8 1/4] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE kan.liang
2020-09-30 7:15 ` Stephane Eranian
2020-09-30 13:51 ` Dave Hansen
2020-09-30 14:42 ` Liang, Kan
2020-09-30 14:48 ` Dave Hansen
2020-09-30 17:17 ` Stephane Eranian [this message]
2020-09-30 17:30 ` Peter Zijlstra
2020-09-30 22:45 ` Stephane Eranian
2020-10-01 13:30 ` Liang, Kan
2020-10-01 13:49 ` Dave Hansen
2020-10-01 14:23 ` Peter Zijlstra
2020-09-21 15:26 ` [PATCH V8 2/4] perf/x86/intel: Support PERF_SAMPLE_DATA_PAGE_SIZE kan.liang
2020-09-21 15:26 ` [PATCH V8 3/4] powerpc/perf: " kan.liang
2020-09-21 15:26 ` [PATCH V8 4/4] perf/core: Add support for PERF_SAMPLE_CODE_PAGE_SIZE kan.liang
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