linux-kernel - Re: [patch V2 25/50] signal: Confine POSIX

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Message-ID: <20240418152308.GA20625@redhat.com>
Date: Thu, 18 Apr 2024 17:23:08 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	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>
Subject: Re: [patch V2 25/50] signal: Confine POSIX_TIMERS properly

On 04/11, Thomas Gleixner wrote:
>
> Move the itimer rearming out of the signal code and consolidate all posix
> timer related functions in the signal code under one ifdef.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  include/linux/posix-timers.h |    5 +
>  kernel/signal.c              |  125 +++++++++++++++----------------------------
>  kernel/time/itimer.c         |   22 +++++++
>  kernel/time/posix-timers.c   |   15 ++++-
>  4 files changed, 82 insertions(+), 85 deletions(-)

Reviewed-by: Oleg Nesterov <oleg@...hat.com>


A minor nit below...

> --- a/include/linux/posix-timers.h
> +++ b/include/linux/posix-timers.h
..
> +static inline void posixtimer_rearm_itimer(struct task_struct *p) { }
> +static inline void posixtimer_rearm(struct kernel_siginfo *info) { }

Do we really need these 2 nops ? please see below.

..

> +		if (unlikely(signr == SIGALRM))
> +			posixtimer_rearm_itimer(tsk);

..

> +	if (IS_ENABLED(CONFIG_POSIX_TIMERS)) {
> +		if (unlikely(resched_timer))
> +			posixtimer_rearm(info);
>  	}

This looks a bit inconsistent to me.

Can't we change the callsite of posixtimer_rearm_itimer() to check
IS_ENABLED(CONFIG_POSIX_TIMERS) too,

		if (IS_ENABLED(CONFIG_POSIX_TIMERS)) {
			if (unlikely(signr == SIGALRM))
				posixtimer_rearm_itimer(tsk);
		}
?

This will make the code more symmetrical, and we can avoid the dumb
definitions of posixtimer_rearm_itimer/posixtimer_rearm.

Oleg.