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From: Thomas Gleixner <tglx@linutronix.de>
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To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Anna-Maria Behnsen
 <anna-maria@linutronix.de>, Benjamin Segall <bsegall@google.com>, Eric
 Dumazet <edumazet@google.com>, Andrey Vagin <avagin@openvz.org>, Pavel
 Tikhomirov <ptikhomirov@virtuozzo.com>, Peter Zijlstra
 <peterz@infradead.org>, Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: [patch V3 17/18] posix-timers: Provide a mechanism to allocate
 a given timer ID
In-Reply-To: <Z9CsstMf-EVZpsiH@pavilion.home>
References: <20250308155501.391430556@linutronix.de>
 <20250308155624.526740902@linutronix.de> <Z9CsstMf-EVZpsiH@pavilion.home>
Date: Tue, 11 Mar 2025 23:05:34 +0100
Message-ID: <87msdrz0i9.ffs@tglx>
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On Tue, Mar 11 2025 at 22:35, Frederic Weisbecker wrote:
> Le Sat, Mar 08, 2025 at 05:48:47PM +0100, Thomas Gleixner a =C3=A9crit :
>> @@ -364,6 +389,16 @@ static enum hrtimer_restart posix_timer_
>>  	return HRTIMER_NORESTART;
>>  }
>>=20=20
>> +long posixtimer_create_prctl(unsigned long ctrl)
>> +{
>> +	if (ctrl > PR_TIMER_CREATE_RESTORE_IDS_ON)
>> +		return -EINVAL;
>> +
>> +	guard(spinlock_irq)(&current->sighand->siglock);
>> +	current->signal->timer_create_restore_ids =3D ctrl =3D=3D PR_TIMER_CRE=
ATE_RESTORE_IDS_ON;
>
> Is the locking necessary here? It's not used on the read side.
> It only makes sense if more flags are to be added later in struct signal =
and the
> fields write can race.

True.

> Also do we want to carry this PR_TIMER_CREATE_RESTORE_IDS_ON accross exec=
? Posix
> timers are removed then anyway.

Indeed, we should clear that.