linux-kernel - Re: [patch 38/44] posix-cpu-timers: Respect INFINITY for hard RTTIME limit

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Date:   Mon, 19 Aug 2019 22:06:50 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        John Stultz <john.stultz@...aro.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: Re: [patch 38/44] posix-cpu-timers: Respect INFINITY for hard RTTIME
 limit


* Thomas Gleixner <tglx@...utronix.de> wrote:

> The RTIME limit expiry code does not check the hard RTTIME limit for
> INFINITY, i.e. being disabled.  Add it.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/time/posix-cpu-timers.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/kernel/time/posix-cpu-timers.c
> +++ b/kernel/time/posix-cpu-timers.c
> @@ -905,7 +905,7 @@ static void check_process_timers(struct
>  		u64 softns, ptime = samples[CPUCLOCK_PROF];
>  		unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
>  
> -		if (psecs >= hard) {
> +		if (hard != RLIM_INFINITY && psecs >= hard) {
>  			/*
>  			 * At the hard limit, we just die.
>  			 * No need to calculate anything else now.

Might make sense to mark this as a possible ABI change in the changelog: 
if some weird code learned to rely on this (arguably broken) behavior 
then the bug turned into an ABI.

Thanks,

	Ingo