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From: Thomas Gleixner <tglx@linutronix.de>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
	"Paul E . McKenney" <paulmck@kernel.org>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"H . Peter Anvin" <hpa@zytor.com>, "Paul Turner" <pjt@google.com>,
	linux-api@vger.kernel.org,
	"Christian Brauner" <brauner@kernel.org>,
	"Florian Weimer" <fw@deneb.enyo.de>,
	David.Laight@ACULAB.COM, carlos@redhat.com,
	"Peter Oskolkov" <posk@posk.io>,
	"Alexander Mikhalitsyn" <alexander@mihalicyn.com>,
	"Chris Kennelly" <ckennelly@google.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Darren Hart" <dvhart@infradead.org>,
	"Davidlohr Bueso" <dave@stgolabs.net>,
	"André Almeida" <andrealmeid@igalia.com>,
	libc-alpha@sourceware.org, "Steven Rostedt" <rostedt@goodmis.org>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Noah Goldstein" <goldstein.w.n@gmail.com>,
	"Daniel Colascione" <dancol@google.com>,
	longman@redhat.com,
	"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>
Subject: Re: [RFC PATCH v2 4/4] selftests/rseq: Implement rseq_mutex test program
Date: Thu, 28 Sep 2023 21:55:20 +0200	[thread overview]
Message-ID: <87v8budqdz.ffs@tglx> (raw)
In-Reply-To: <20230529191416.53955-5-mathieu.desnoyers@efficios.com>

On Mon, May 29 2023 at 15:14, Mathieu Desnoyers wrote:
> +static void rseq_lock_slowpath(struct rseq_mutex *lock)
> +{
> +	int i = 0;
> +
> +	for (;;) {
> +		struct rseq_abi_sched_state *expected = NULL, *self = rseq_get_sched_state(rseq_get_abi());
> +
> +		if (__atomic_compare_exchange_n(&lock->owner, &expected, self, false,
> +						__ATOMIC_ACQUIRE, __ATOMIC_RELAXED))
> +			break;
> +		//TODO: use rseq critical section to protect dereference of owner thread's
> +		//rseq_abi_sched_state, combined with rseq fence at thread reclaim.
> +		if ((RSEQ_READ_ONCE(expected->state) & RSEQ_ABI_SCHED_STATE_FLAG_ON_CPU) &&

For robust and PI futexes the futex value is an ABI between kernel and
user space. Sure, this is only meant for demonstration, but it's the
wrong direction.

Thanks,

        tglx







      reply	other threads:[~2023-09-28 19:55 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-29 19:14 [RFC PATCH v2 0/4] Extend rseq with sched_state_ptr field Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 1/4] rseq: Add sched_state field to struct rseq Mathieu Desnoyers
2023-05-29 19:35   ` Florian Weimer
2023-05-29 19:48     ` Mathieu Desnoyers
2023-05-30  8:20       ` Florian Weimer
2023-05-30 14:25         ` Mathieu Desnoyers
2023-05-30 15:13           ` Mathieu Desnoyers
2023-09-26 20:52       ` Dmitry Vyukov
2023-09-26 23:49         ` Dmitry Vyukov
2023-09-26 23:54           ` Dmitry Vyukov
2023-09-27  4:51           ` Florian Weimer
2023-09-27 15:58             ` Dmitry Vyukov
2023-09-28  8:52               ` Florian Weimer
2023-09-28 14:44                 ` Dmitry Vyukov
2023-09-28 14:47           ` Dmitry Vyukov
2023-09-28 10:39   ` Peter Zijlstra
2023-09-28 11:22     ` David Laight
2023-09-28 13:20       ` Mathieu Desnoyers
2023-09-28 14:26         ` Peter Zijlstra
2023-09-28 14:33         ` David Laight
2023-09-28 15:05         ` André Almeida
2023-09-28 14:43     ` Steven Rostedt
2023-09-28 15:51       ` David Laight
2023-10-02 16:51         ` Steven Rostedt
2023-10-02 17:22           ` David Laight
2023-10-02 17:56             ` Steven Rostedt
2023-09-28 20:21   ` Thomas Gleixner
2023-09-28 20:43     ` Mathieu Desnoyers
2023-09-28 20:54   ` Thomas Gleixner
2023-09-28 22:11     ` Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 2/4] selftests/rseq: Add sched_state rseq field and getter Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 3/4] selftests/rseq: Implement sched state test program Mathieu Desnoyers
2023-05-29 19:14 ` [RFC PATCH v2 4/4] selftests/rseq: Implement rseq_mutex " Mathieu Desnoyers
2023-09-28 19:55   ` Thomas Gleixner [this message]

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