linux-kernel - Re: [PATCH/RFC] core/nfsd: allow kernel threads to use task

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Message-ID: <20231128142018.GA24108@redhat.com>
Date:   Tue, 28 Nov 2023 15:20:18 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     NeilBrown <neilb@...e.de>, Al Viro <viro@...iv.linux.org.uk>
Cc:     Christian Brauner <brauner@...nel.org>,
        Jens Axboe <axboe@...nel.dk>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org
Subject: Re: [PATCH/RFC] core/nfsd: allow kernel threads to use task_work.

On 11/28, Oleg Nesterov wrote:
>
> On a related note... Neil, Al, et al, can you look at
>
> 	[PATCH 1/3] fput: don't abuse task_work_add() when possible
> 	https://lore.kernel.org/all/20150908171446.GA14589@redhat.com/

Cough... Now that I look at this 8 years old patch again I think
it is wrong, fput() can race with task_work_cancel() so it is not
safe to dereference the first pending work in theory :/

Oleg.