linux-kernel - RE: [patch V2 2/5] posix-cpu-timers: Convert the flags to a bitmap

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Date:   Tue, 21 Jul 2020 20:30:02 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     David Laight <David.Laight@...LAB.COM>,
        Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "x86\@kernel.org" <x86@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        John Stultz <john.stultz@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: RE: [patch V2 2/5] posix-cpu-timers: Convert the flags to a bitmap

David Laight <David.Laight@...LAB.COM> writes:
> From: Thomas Gleixner
>> Sent: 21 July 2020 17:11
>> 
>> Frederic Weisbecker <frederic@...nel.org> writes:
>> > On Thu, Jul 16, 2020 at 10:19:25PM +0200, Thomas Gleixner wrote:
>> >> --- a/kernel/time/posix-cpu-timers.c
>> >> +++ b/kernel/time/posix-cpu-timers.c
>> >> @@ -25,7 +25,7 @@ void posix_cputimers_group_init(struct p
>> >>  	posix_cputimers_init(pct);
>> >>  	if (cpu_limit != RLIM_INFINITY) {
>> >>  		pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
>> >> -		pct->timers_active = true;
>> >> +		set_bit(CPUTIMERS_ACTIVE, &pct->flags);
>> >
>> > I guess this one could be __set_bit().
>> 
>> True :)
>
> Hmmm... does this code need the bit operations to be atmomic?
> If not then an bitmap is completely the wrong thing to be using.

Some of it does, otherwise the booleans would have stayed, but I'm
reworking parts of it so this might change.

Thanks,

        tglx