linux-kernel - Re: [PATCH 3/4] locking/mutex: Pass proper call-site ip

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Date:   Tue, 1 Mar 2022 10:05:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Byungchul Park <byungchul.park@....com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
        bpf@...r.kernel.org, Radoslaw Burny <rburny@...gle.com>
Subject: Re: [PATCH 3/4] locking/mutex: Pass proper call-site ip

On Mon, Feb 28, 2022 at 05:04:11PM -0800, Namhyung Kim wrote:
> The __mutex_lock_slowpath() and friends are declared as noinline and
> _RET_IP_ returns its caller as mutex_lock which is not meaningful.
> Pass the ip from mutex_lock() to have actual caller info in the trace.

Blergh, can't you do a very limited unwind when you do the tracing
instead? 3 or 4 levels should be plenty fast and sufficient.