linux-kernel - Re: [patch V2 08/17] posix-timers: Rework timer removal

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Message-ID: <8734fn53b5.ffs@tglx>
Date: Sat, 08 Mar 2025 09:34:06 +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>, Benjamin Segall <bsegall@...gle.com>, Eric
 Dumazet <edumazet@...gle.com>, Andrey Vagin <avagin@...nvz.org>, Pavel
 Tikhomirov <ptikhomirov@...tuozzo.com>, Peter Zijlstra
 <peterz@...radead.org>
Subject: Re: [patch V2 08/17] posix-timers: Rework timer removal

On Sat, Mar 08 2025 at 00:03, Frederic Weisbecker wrote:
> Le Sun, Mar 02, 2025 at 08:36:56PM +0100, Thomas Gleixner a écrit :
>> --- a/include/linux/posix-timers.h
>> +++ b/include/linux/posix-timers.h
>> @@ -240,6 +240,13 @@ static inline void posixtimer_sigqueue_p
>>  
>>  	posixtimer_putref(tmr);
>>  }
>> +
>> +static inline bool posixtimer_valid(const struct k_itimer *timer)
>> +{
>> +	unsigned long val = (unsigned long)timer->it_signal;
>> +
>> +	return !(val & 0x1UL);
>> +}
>>  #else  /* CONFIG_POSIX_TIMERS */
>>  static inline void posixtimer_sigqueue_getref(struct sigqueue *q) { }
>>  static inline void posixtimer_sigqueue_putref(struct sigqueue *q) { }
>> --- a/kernel/signal.c
>> +++ b/kernel/signal.c
>> @@ -2092,7 +2092,7 @@ static inline void posixtimer_sig_ignore
>>  	 * from a non-periodic timer, then just drop the reference
>>  	 * count. Otherwise queue it on the ignored list.
>>  	 */
>> -	if (tmr->it_signal && tmr->it_sig_periodic)
>> +	if (posixtimer_valid(tmr) && tmr->it_sig_periodic)
>>  		hlist_add_head(&tmr->ignored_list, &tsk->signal->ignored_posix_timers);
>>  	else
>>  		posixtimer_putref(tmr);
>> --- a/kernel/time/posix-timers.c
>> +++ b/kernel/time/posix-timers.c
>> @@ -279,7 +279,7 @@ static bool __posixtimer_deliver_signal(
>>  	 * since the signal was queued. In either case, don't rearm and
>>  	 * drop the signal.
>>  	 */
>> -	if (timr->it_signal_seq != timr->it_sigqueue_seq || WARN_ON_ONCE(!timr->it_signal))
>> +	if (timr->it_signal_seq != timr->it_sigqueue_seq || !posixtimer_valid(timr))
>
> Hmm, should it still warn here? ie: WARN_ON_ONCE(!posixtimer_valid(timr)) ?

No, because the timer is invalidated early now.

Thanks,

        tglx