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From: Thomas Gleixner <tglx@kernel.org>
To: "André Almeida" <andrealmeid@igalia.com>,
	"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org, Carlos O'Donell <carlos@redhat.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Florian Weimer <fweimer@redhat.com>,
	Rich Felker <dalias@aerifal.cx>,
	Torvald Riegel <triegel@redhat.com>,
	Darren Hart <dvhart@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Arnd Bergmann <arnd@arndb.de>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>
Subject: Re: [RFC PATCH] futex: Introduce __vdso_robust_futex_unlock
Date: Thu, 12 Mar 2026 21:19:56 +0100	[thread overview]
Message-ID: <87ikb0pzpv.ffs@tglx> (raw)
In-Reply-To: <2993f778-c4f4-4aa8-8e42-1dca4d5e29e1@igalia.com>

On Thu, Mar 12 2026 at 10:46, André Almeida wrote:
> Em 11/03/2026 15:54, Mathieu Desnoyers escreveu:
> I would also have `uval` instead of `val = 0`, because even though the 
> most common semanthics for futex is that (LOCK_FREE == 0), futex has no 
> predetermined semanthics of what each value means, and the userspace is 
> free to choose what value they want to choose for a free lock.

That's true for non-robust futexes, but robust futexes have clearly
defined semantics vs. the userspace value:

        0:	unlocked
        != 0:	PID of the owner

So uval is useless as the unlock value can't be anything else than 0,
no?

Thanks,

        tglx

  parent reply	other threads:[~2026-03-12 20:20 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-11 18:54 [RFC PATCH] futex: Introduce __vdso_robust_futex_unlock Mathieu Desnoyers
2026-03-11 20:11 ` Mathieu Desnoyers
2026-03-12  8:49 ` Florian Weimer
2026-03-12 13:13   ` Mathieu Desnoyers
2026-03-12 14:12     ` Florian Weimer
2026-03-12 14:14       ` André Almeida
2026-03-12 16:09         ` Mathieu Desnoyers
2026-03-12 13:46 ` André Almeida
2026-03-12 14:04   ` Mathieu Desnoyers
2026-03-12 18:40     ` Mathieu Desnoyers
2026-03-12 18:58       ` André Almeida
2026-03-12 19:10     ` Thomas Gleixner
2026-03-12 19:16       ` Mathieu Desnoyers
2026-03-13  8:20         ` Florian Weimer
2026-03-12 20:19   ` Thomas Gleixner [this message]
2026-03-12 21:28     ` Mathieu Desnoyers
2026-03-12 22:23 ` Thomas Gleixner
2026-03-12 22:52   ` Mathieu Desnoyers
2026-03-13 12:12     ` Sebastian Andrzej Siewior
2026-03-13 12:17       ` Mathieu Desnoyers
2026-03-13 13:29         ` Sebastian Andrzej Siewior
2026-03-13 13:35           ` Mathieu Desnoyers
2026-03-16 17:12     ` Thomas Gleixner
2026-03-16 19:36       ` Mathieu Desnoyers
2026-03-16 20:27         ` Thomas Gleixner
2026-03-16 21:01           ` Mathieu Desnoyers
2026-03-16 22:19             ` Thomas Gleixner
2026-03-16 22:30               ` Mathieu Desnoyers
2026-03-16 23:29                 ` Thomas Gleixner
2026-03-20 18:13                   ` Mathieu Desnoyers
2026-03-24 21:35                     ` Thomas Gleixner
2026-03-25 14:12                       ` Mathieu Desnoyers

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