linux-kernel - Re: [PATCH] rlimits: do not grab tasklist_lock for do

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Date:   Mon, 20 Dec 2021 00:30:10 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Barret Rhoden <brho@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexey Gladkov <legion@...nel.org>,
        William Cohen <wcohen@...hat.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Chris Hyser <chris.hyser@...cle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Xiaofeng Cao <caoxiaofeng@...ong.com>,
        David Hildenbrand <david@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rlimits: do not grab tasklist_lock for do_prlimit on
 current

On Wed, Dec 15, 2021 at 01:42:32PM -0600, Eric W. Biederman wrote:
...
> 
> > If it's too much of a risk/ugliness for not clear enough gain (in code
> > quality or performance), I'm fine with dropping it.
> 
> Removing the tasklist_lock where we can is definitely a clear gain.
> 
> Simply shoving tasklist_lock aside and making the code more complicated
> is much less clear.
> 
> Plus anything you can benchmark (even microbenchmark) and show the
> benefit of is welcome.  Especially when you have indications that it
> makes a difference in a larger context.

Thanks for looking into this, Eric! I must confess I've a vague memory
about this code. Still while you're talking about cleanup I wonder if
we should make do_prlimit() being a static function, not global as it
now.