From: Petr Malat <oss@malat.biz>
To: Jiri Olsa <jolsa@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
Alexey Budankov <alexey.budankov@linux.intel.com>
Subject: Re: [PATCH v2 1/3] Revert "perf session: Fix decompression of PERF_RECORD_COMPRESSED records"
Date: Tue, 24 Nov 2020 19:15:19 +0100 [thread overview]
Message-ID: <20201124181519.GA29264@ntb.petris.klfree.czf> (raw)
In-Reply-To: <20201124143645.GD2088148@krava>
Hi!
On Tue, Nov 24, 2020 at 03:36:45PM +0100, Jiri Olsa wrote:
> On Tue, Nov 24, 2020 at 11:29:15AM +0100, Petr Malat wrote:
> > Both mmapped and compressed events can be split by the buffer boundary,
> > it doesn't make sense to handle them differently.
> I'm going to need more than this, if there's a problem
> with current code please share more details, what's
> broken and how it shows
It's easy to trigger the problem - make a perf recording larger than
MMAP_SIZE (32MB on 32-bit platform) and run perf report on it. There
is a small chance recorded events will be aligned on the 32 MB
boundary and in that case just repeat the test.
The problem was introduced by "perf session: Avoid infinite loop when
seeing invalid header.size", which instead of aborting the execution
when there is a truncated event at the end of the file just terminated
execution whenever there is a split event. Later then the problem has
been noticed for compressed events and fixed by "perf session: Fix
decompression of PERF_RECORD_COMPRESSED records" by effectively
reverting "perf session: Avoid infinite loop when seeing invalid
header.size" for compressed events, which left uncompressed events
broken.
I think the best is to revert these 2 changes and fix the original
problem by aborting when there is no actual shift during remapping - as
long as we shift, it's clear we must approach the end of the file so
such an algorithm can't loop forever.
BR,
Petr
next prev parent reply other threads:[~2020-11-24 18:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-24 9:59 [PATCH 1/3] Revert "perf session: Fix decompression of PERF_RECORD_COMPRESSED records" Petr Malat
2020-11-24 9:59 ` [PATCH 2/3] Revert "perf session: Avoid infinite loop when seeing invalid header.size" Petr Malat
2020-11-24 9:59 ` [PATCH 3/3] perf session: Avoid infinite loop if an event is truncated Petr Malat
2020-11-24 10:21 ` Petr Malat
2020-11-24 10:29 ` [PATCH v2 1/3] Revert "perf session: Fix decompression of PERF_RECORD_COMPRESSED records" Petr Malat
2020-11-24 10:29 ` [PATCH v2 2/3] Revert "perf session: Avoid infinite loop when seeing invalid header.size" Petr Malat
2020-11-24 10:29 ` [PATCH v2 3/3] perf session: Avoid infinite loop if an event is truncated Petr Malat
2020-11-24 14:36 ` [PATCH v2 1/3] Revert "perf session: Fix decompression of PERF_RECORD_COMPRESSED records" Jiri Olsa
2020-11-24 18:15 ` Petr Malat [this message]
2020-11-30 11:40 ` Petr Malat
2020-12-01 19:09 ` Jiri Olsa
2020-12-01 21:04 ` Alexei Budankov
2020-12-01 21:28 ` Alexei Budankov
2020-12-02 14:04 ` Bayduraev, Alexey V
2020-12-02 14:18 ` Alexei Budankov
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