linux-kernel - Re: [BUG] perf segfaults when combining --overwrite and intel

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Message-ID: <CAP4=nvTdD=eKcO_sJL3G7U0KxRTQ6XjJeJxNrmeD3n8UGBv5+g@mail.gmail.com>
Date: Mon, 28 Apr 2025 16:16:58 +0200
From: Tomas Glozar <tglozar@...hat.com>
To: Leo Yan <leo.yan@....com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, linux-perf-users@...r.kernel.org, 
	LKML <linux-kernel@...r.kernel.org>, Wander Costa <wcosta@...hat.com>
Subject: Re: [BUG] perf segfaults when combining --overwrite and intel_pt event

po 28. 4. 2025 v 14:47 odesílatel Leo Yan <leo.yan@....com> napsal:
> I would leave this fix to the Intel-PT developers, who know this part
> best.

Makes sense.

Just FYI, I tried applying the patch above, and after swapping
mmap_ovw for overwrite_mmap (which appears to be the correct name in
struct evlist) to make it build, the segfaults are gone:

$ perf record --overwrite -a -e intel_pt/cyc,noretcomp/k sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 40,533 MB perf.data

However, the data cannot be read:

$ perf report
0x7620 [0x30]: failed to process type: 71 [Invalid argument]
Error:
failed to process sample
# To display the perf.data header info, please use
--header/--header-only options.
#

Data generated without --overwrite is fine.

Tomas