linux-kernel - Re: [PATCH 0/2] sched/membarrier, selftests: Introduce MEMBARRIER_CMD_GET

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Message-ID: <20221223010505.GT4001@paulmck-ThinkPad-P17-Gen-1>
Date:   Thu, 22 Dec 2022 17:05:05 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Michal Clapinski <mclapinski@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andrei Vagin <avagin@...il.com>, Shuah Khan <shuah@...nel.org>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 0/2] sched/membarrier, selftests: Introduce
 MEMBARRIER_CMD_GET_REGISTRATIONS

On Thu, Dec 22, 2022 at 10:28:28AM -0500, Mathieu Desnoyers wrote:
> On 2022-12-07 11:43, Michal Clapinski wrote:
> > This change provides a method to query previously issued registrations.
> > It's needed for CRIU (checkpoint/restore in userspace). Before this
> > change we had to issue private membarrier commands during checkpoint -
> > if they succeeded, they must have been registered. Unfortunately global
> > membarrier succeeds even on unregistered processes, so there was no way to
> > tell if MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED had been issued or not.
> > 
> > CRIU is run after the process has been frozen with ptrace, so we don't
> > have to worry too much about the result of running this command in parallel
> > with registration commands.
> 
> Peter, Paul, I'm OK with the proposed changes. Should we route this through
> sched/core from the tip tree ?
> 
> For both patches:
> 
> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

Also for both patches:

Acked-by: Paul E. McKenney <paulmck@...nel.org>

> Thanks,
> 
> Mathieu
> 
> > 
> > Michal Clapinski (2):
> >    sched/membarrier: Introduce MEMBARRIER_CMD_GET_REGISTRATIONS
> >    selftests/membarrier: Test MEMBARRIER_CMD_GET_REGISTRATIONS
> > 
> >   include/uapi/linux/membarrier.h               |  4 ++
> >   kernel/sched/membarrier.c                     | 39 ++++++++++++++++++-
> >   .../membarrier/membarrier_test_impl.h         | 33 ++++++++++++++++
> >   .../membarrier/membarrier_test_multi_thread.c |  2 +-
> >   .../membarrier_test_single_thread.c           |  6 ++-
> >   5 files changed, 81 insertions(+), 3 deletions(-)
> > 
> 
> -- 
> Mathieu Desnoyers
> EfficiOS Inc.
> https://www.efficios.com
>