linux-kernel - Re: [patch v6 02/20] posix-timers: Make signal overrun accounting sensible

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Message-ID: <877c9mvgh7.ffs@tglx>
Date: Fri, 01 Nov 2024 21:36:36 +0100
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 v6 02/20] posix-timers: Make signal overrun accounting
 sensible

On Fri, Nov 01 2024 at 13:51, Frederic Weisbecker wrote:
> Le Thu, Oct 31, 2024 at 04:46:25PM +0100, Thomas Gleixner a écrit :
>> @@ -1968,15 +1968,9 @@ int send_sigqueue(struct sigqueue *q, st
>>  
>>  	ret = 0;
>>  	if (unlikely(!list_empty(&q->list))) {
>> -		/*
>> -		 * If an SI_TIMER entry is already queue just increment
>> -		 * the overrun count.
>> -		 */
>> -		q->info.si_overrun++;
>>  		result = TRACE_SIGNAL_ALREADY_PENDING;
>>  		goto out;
>>  	}
>> -	q->info.si_overrun = 0;
>
> So it's not cleared anymore on signal queue?
>
> Not sure if it's a big problem but if an interval timer gets a signal with
> overruns and then the timer is reset later as non interval, the resulting
> upcoming signals will still carry the previous non-zero overruns?

Duh. Yes.

> However it's better to keep the overrun update on a single place so
> perhaps this?
>
> diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
> index 66ed49efc02f..f06c52731d65 100644
> --- a/kernel/time/posix-timers.c
> +++ b/kernel/time/posix-timers.c
> @@ -282,6 +282,8 @@ bool posixtimer_deliver_signal(struct kernel_siginfo *info)
>  		++timr->it_signal_seq;
>  
>  		info->si_overrun = timer_overrun_to_int(timr);
> +	} else {
> +		info->si_overrun = 0;
>  	}
>  	ret = true;
>  
> Other than that:

Let me fold that.

> Reviewed-by: Frederic Weisbecker <frederic@...nel.org>