linux-kernel - Re: [patch 12/45] posix-cpu-timers: Simplify posix_cpu_timer

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Message-ID: <87y1k2153p.ffs@tglx>
Date:   Thu, 29 Jun 2023 20:43:54 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>
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 12/45] posix-cpu-timers: Simplify posix_cpu_timer_set()

On Tue, Jun 27 2023 at 12:51, Frederic Weisbecker wrote:
> On Tue, Jun 06, 2023 at 04:37:37PM +0200, Thomas Gleixner wrote:
>> Avoid the late sighand lock/unlock dance when a timer is not armed to
>> enforce reevaluation of the timer base so that the process wide CPU timer
>> sampling can be disabled.
>> +	 * SIGEV_NONE timers are never armed. In case the timer is not
>> +	 * armed, enforce the reevaluation of the timer base so that the
>> +	 * process wide cputime counter can be disabled eventually.
>>  	 */
>>  	if (!sigev_none && new_expires && now < new_expires)
>>  		arm_timer(timer, p);
>> +	else
>> +		trigger_base_recalc_expires(timer, p);
>
> We don't need a recalc if sigev_none, right?

Correct.