linux-kernel - Re: [patch 14/45] posix-timers: Consolidate interval retrieval

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Date:   Fri, 30 Jun 2023 13:25:17 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        John Stultz <jstultz@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [patch 14/45] posix-timers: Consolidate interval retrieval

On Thu, Jun 29, 2023 at 08:47:30PM +0200, Thomas Gleixner wrote:
> On Wed, Jun 28 2023 at 15:08, Frederic Weisbecker wrote:
> 
> > Le Tue, Jun 06, 2023 at 04:37:40PM +0200, Thomas Gleixner a écrit :
> >> There is no point to collect the current interval in the posix clock
> >> specific settime() and gettime() callbacks. Just do it right in the common
> >> code.
> >> 
> >> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> >
> > The only difference I see is that we now return the old interval
> > even if the target is reaped, which probably doesn't matter anyway.
> 
> But we don't return it to user space because ret != 0 in that case.

In the case of ->set yes but in the case of ->get there is no error
handling.

But still this shouldn't matter as the task is fetched under rcu protection.
And also it can be reaped by the time we return to userspace, so this is
inherently racy. Well, the effect could be visible if current is the reaper
and it has reaped the target already, then it could expect a 0 value in the
interval. I don't think we care though.

Thanks.