linux-kernel - Re: [PATCH v3 00/19] unwind, perf: sframe user space unwinding

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Message-ID: <20241028235556.oyoyt3uvlau5vzsd@treble.attlocal.net>
Date: Mon, 28 Oct 2024 16:55:56 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, Indu Bhagat <indu.bhagat@...cle.com>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>,
	Sam James <sam@...too.org>, linux-trace-kernel@...r.kerne.org,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Jens Remus <jremus@...ux.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v3 00/19] unwind, perf: sframe user space unwinding

On Mon, Oct 28, 2024 at 02:47:27PM -0700, Josh Poimboeuf wrote:
> This has all the changes discussed in v2, plus VDSO sframe support and
> Namhyung's perf tool patches (see detailed changelog below).
> 
> I did quite a bit of testing, it seems to work well.  It still needs
> some binutils and glibc patches which I'll send in a reply.
> 
> Questions for perf experts:
> 
>   - Is the perf_event lifetime managed correctly or do we need to do
>     something to ensure it exists in unwind_user_task_work()?
> 
>     Or alternatively is the original perf_event even needed in
>     unwind_user_task_work() or can a new one be created on demand?
> 
>   - Is --call-graph=sframe needed for consistency?
> 
>   - Should perf use the context cookie?  Note that because the callback
>     is usually only called once for multiple NMIs in the same entry
>     context, it's possible for the PERF_RECORD_CALLCHAIN_DEFERRED event
>     to arrive *before* some of the corresponding kernel events.  The
>     context cookie disambiguates the corner cases.
> 
> Based on tip/master.
> 
> Also at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git sframe-v3

Argh, apparently it's a bad idea to pass "*.patch" twice on the
git-send-email cmdline ;-)  Sorry for sending it twice!

-- 
Josh