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

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Message-ID: <9fad5641-ebd4-d2e5-6f87-2c409c336072@efficios.com>
Date:   Thu, 22 Dec 2022 10:28:28 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Michal Clapinski <mclapinski@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     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 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>

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