linux-kernel - Re: [PATCH 3/3] ring_buffer: Use try

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Date:   Wed, 1 Mar 2023 19:37:06 +0100
From:   Uros Bizjak <ubizjak@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 3/3] ring_buffer: Use try_cmpxchg instead of cmpxchg

On Wed, Mar 1, 2023 at 7:28 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 1 Mar 2023 13:18:31 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
>
> > I am leaning to just taking this, and hope that it doesn't cause problems.
> > And I would really love to change all the local_cmpxchg() to
> > local_try_cmpxchg(). Hmm, I wonder how much of an effort that would be to
> > implement those?
>
> I see that you were the one that added the generic support for
> try_cmpxchg64() and messed with all those generated files. Care to add one
> for local_try_cmpxchg() ;-)

I already have a half-written patch that implements local_try_cmpxchg.
Half-written in the sense that above-mentioned scripts generate
correct locking primitives, but the fallback code for local_cmpxchg is
a bit different that the fallback code for cmpxchg. There is an effort
to unify all cmpxchg stuff (cmpxchg128 will be introduced) and I think
that local_cmpxchg should also be handled in the same way. So, if
there is interest, I can find some time to finish the infrastructure
patch and convert the uses. But this is quite an undertaking that will
take some time.

Uros.