linux-kernel - Re: PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf unwinding

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Message-ID: <20181106172607.GT6218@tassilo.jf.intel.com>
Date:   Tue, 6 Nov 2018 09:26:07 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Milian Wolff <milian.wolff@...b.com>, linux-kernel@...r.kernel.org,
        Jiri Olsa <jolsa@...nel.org>, namhyung@...nel.org,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho <acme@...nel.org>
Subject: Re: PEBS level 2/3 breaks dwarf unwinding! [WAS: Re: Broken dwarf
 unwinding - wrong stack pointer register value?]

> hum, is this about having 'large pebs' or there's this window
> if there's also only single pebs record allowed? which should
> be case for dwarf unwind

With large PEBS today there is never any stack unwind because
stack unwinding can be only done from a PMI.

The window happens even with single PEBS. It's related
to the CPU being pipelined, so complex events may not
happen fully atomically.

-Andi