From: Peter Zijlstra <peterz@infradead.org>
To: Suleiman Souhlal <suleiman@google.com>
Cc: linux-kernel@vger.kernel.org, "Thomas Gleixner" <tglx@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Darren Hart" <dvhart@infradead.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"André Almeida" <andrealmeid@igalia.com>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
"Valentin Schneider" <vschneid@redhat.com>,
"K Prateek Nayak" <kprateek.nayak@amd.com>,
"zhidao su" <soolaugust@gmail.com>,
"John Stultz" <jstultz@google.com>,
"Qais Yousef" <qyousef@google.com>,
ssouhlal@freebsd.org
Subject: Re: [RFC PATCH 02/12] futex: Switch PI futex to use p->pi_futex_lock instead of p->pi_lock.
Date: Thu, 17 Sep 2026 17:38:31 +0200 [thread overview]
Message-ID: <20260917153831.GL4121339@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260917043339.2093426-3-suleiman@google.com>
On Thu, Sep 17, 2026 at 04:33:26AM +0000, Suleiman Souhlal wrote:
> Switch PI futexes to use p->pi_futex_lock instead of p->pi_lock.
>
> When augmenting PING futexes with proxy execution, we get lock order
> inversions, due to the lock order being p->pi_lock -> mutex->wait_lock
> in the scheduler, but wait_lock -> p->pi_lock in futex code.
>
> So move the futex code to use a new lock, p->pi_futex_lock, to
> protect p->pi_state_list and pi_state->owner.
This is of course horrible. Lets not do this.
next prev parent reply other threads:[~2026-09-17 15:38 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 4:33 [RFC PATCH 00/12] FUTEX_PING: A stealable futex using Proxy Execution Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 01/12] sched: Abstract task_struct->blocked_on by locking primitive Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 02/12] futex: Switch PI futex to use p->pi_futex_lock instead of p->pi_lock Suleiman Souhlal
2026-09-17 15:38 ` Peter Zijlstra [this message]
2026-09-18 7:11 ` Suleiman Souhlal
2026-09-18 10:07 ` K Prateek Nayak
2026-09-18 12:06 ` Peter Zijlstra
2026-09-17 4:33 ` [RFC PATCH 03/12] futex: Add "ping" parameter to pi_state management functions and export them Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 04/12] futex: Introduce stealable PI futex, FUTEX_*_PING Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 05/12] futex: Implement exit_ping_state_list() Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 06/12] futex: Address aborting from futex_lock_ping() while owning ping_state Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 07/12] futex: Make FUTEX_*_PING use Proxy Execution Suleiman Souhlal
2026-09-17 13:18 ` Jihan LIN
2026-09-17 14:39 ` K Prateek Nayak
2026-09-17 15:36 ` Peter Zijlstra
2026-09-17 4:33 ` [RFC PATCH 08/12] futex: Implement PING futex handoff Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 09/12] futex: Wake up donor in PING futex unlock Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 10/12] futex: Optimistic spinning for PING futexes Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 11/12] futex: Allow userspace stealing " Suleiman Souhlal
2026-09-17 4:33 ` [RFC PATCH 12/12] tools/testing/futex: Add ping_bench, a tool for benchmarking futexes Suleiman Souhlal
2026-09-17 8:58 ` [RFC PATCH 00/12] FUTEX_PING: A stealable futex using Proxy Execution Peter Zijlstra
2026-09-17 17:53 ` John Stultz
2026-09-17 18:51 ` Steven Rostedt
2026-09-18 6:30 ` Suleiman Souhlal
2026-09-18 8:25 ` Peter Zijlstra
2026-09-18 6:07 ` Suleiman Souhlal
2026-09-18 8:07 ` Peter Zijlstra
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