linux-kernel - Re: [PATCH 2/4] locking: Apply contention tracepoints in the slow path

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Date:   Tue, 1 Mar 2022 10:14:05 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        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>,
        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 <bpf@...r.kernel.org>, Radoslaw Burny <rburny@...gle.com>
Subject: Re: [PATCH 2/4] locking: Apply contention tracepoints in the slow path

Hi Steve,

On Tue, Mar 1, 2022 at 6:45 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 1 Mar 2022 10:03:54 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:
>
> > diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
> > index 8555c4efe97c..18b9f4bf6f34 100644
> > --- a/kernel/locking/rtmutex.c
> > +++ b/kernel/locking/rtmutex.c
> > @@ -1579,6 +1579,8 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
> >
> >       set_current_state(state);
> >
> > +     trace_contention_begin(lock, _RET_IP_, LCB_F_RT);
>
> I guess one issue with this is that _RET_IP_ will return the rt_mutex
> address if this is not inlined, making the _RET_IP_ rather useless.
>
> Now, if we can pass the _RET_IP_ into __rt_mutex_slowlock() then we could
> reference that.

Right, that's what I did in patch 03 and 04 for mutex and rwsem.
But I forgot to update rt_mutex, will fix.

Thanks,
Namhyung