From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
"André Almeida" <andrealmeid@igalia.com>,
"Darren Hart" <dvhart@infradead.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"Ingo Molnar" <mingo@redhat.com>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Valentin Schneider" <vschneid@redhat.com>,
"Waiman Long" <longman@redhat.com>
Subject: Re: [PATCH v10 00/21] futex: Add support task local hash maps, FUTEX2_NUMA and FUTEX2_MPOL
Date: Fri, 14 Mar 2025 11:42:59 +0100 [thread overview]
Message-ID: <20250314104259.GA36322@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250312151848.RlB_XuHA@linutronix.de>
On Wed, Mar 12, 2025 at 04:18:48PM +0100, Sebastian Andrzej Siewior wrote:
> @@ -196,12 +196,12 @@ static bool __futex_pivot_hash(struct mm_struct *mm,
> {
> struct futex_private_hash *fph;
>
> - lockdep_assert_held(&mm->futex_hash_lock);
> WARN_ON_ONCE(mm->futex_phash_new);
>
> - fph = mm->futex_phash;
> + fph = rcu_dereference_protected(mm->futex_phash,
> + lockdep_is_held(&mm->futex_hash_lock));
I are confused... this makes no sense. Why ?!
We only ever write that variable while holding this lock, we hold the
lock, we don't need RCU to read the variable.
next prev parent reply other threads:[~2025-03-14 10:43 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-12 15:16 [PATCH v10 00/21] futex: Add support task local hash maps, FUTEX2_NUMA and FUTEX2_MPOL Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 01/21] rcuref: Provide rcuref_is_dead() Sebastian Andrzej Siewior
2025-03-13 4:23 ` Joel Fernandes
2025-03-13 7:55 ` Sebastian Andrzej Siewior
2025-03-14 10:36 ` Peter Zijlstra
2025-03-12 15:16 ` [PATCH v10 02/21] futex: Move futex_queue() into futex_wait_setup() Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 03/21] futex: Pull futex_hash() out of futex_q_lock() Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 04/21] futex: Create hb scopes Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 05/21] futex: Create futex_hash() get/put class Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 06/21] futex: Create helper function to initialize a hash slot Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 07/21] futex: Add basic infrastructure for local task local hash Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 08/21] futex: Hash only the address for private futexes Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 09/21] futex: Allow automatic allocation of process wide futex hash Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 10/21] futex: Decrease the waiter count before the unlock operation Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 11/21] futex: Introduce futex_q_lockptr_lock() Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 12/21] futex: Acquire a hash reference in futex_wait_multiple_setup() Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 13/21] futex: Allow to re-allocate the private local hash Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 14/21] futex: Resize local futex hash table based on number of threads Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 15/21] futex: s/hb_p/fph/ Sebastian Andrzej Siewior
2025-03-14 12:36 ` Peter Zijlstra
2025-03-14 13:10 ` Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 16/21] futex: Remove superfluous state Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 17/21] futex: Untangle and naming Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 18/21] futex: Rework SET_SLOTS Sebastian Andrzej Siewior
2025-03-26 15:37 ` Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 19/21] mm: Add vmalloc_huge_node() Sebastian Andrzej Siewior
2025-03-12 22:02 ` Andrew Morton
2025-03-13 7:59 ` Sebastian Andrzej Siewior
2025-03-13 22:08 ` Andrew Morton
2025-03-14 9:59 ` Sebastian Andrzej Siewior
2025-03-14 10:34 ` Andrew Morton
2025-03-12 15:16 ` [PATCH v10 20/21] futex: Implement FUTEX2_NUMA Sebastian Andrzej Siewior
2025-03-25 19:52 ` Shrikanth Hegde
2025-03-25 22:52 ` Peter Zijlstra
2025-03-25 22:56 ` Peter Zijlstra
2025-03-26 12:57 ` Shrikanth Hegde
2025-03-26 13:37 ` Peter Zijlstra
2025-03-26 15:06 ` Shrikanth Hegde
2025-03-26 8:03 ` Sebastian Andrzej Siewior
2025-03-12 15:16 ` [PATCH v10 21/21] futex: Implement FUTEX2_MPOL Sebastian Andrzej Siewior
2025-03-12 15:18 ` [PATCH v10 00/21] futex: Add support task local hash maps, FUTEX2_NUMA and FUTEX2_MPOL Sebastian Andrzej Siewior
2025-03-14 10:42 ` Peter Zijlstra [this message]
2025-03-14 10:58 ` Peter Zijlstra
2025-03-14 11:28 ` Sebastian Andrzej Siewior
2025-03-14 11:41 ` Peter Zijlstra
2025-03-14 12:00 ` Sebastian Andrzej Siewior
2025-03-14 12:30 ` Peter Zijlstra
2025-03-14 13:30 ` Sebastian Andrzej Siewior
2025-03-14 14:18 ` Peter Zijlstra
2025-03-14 14:40 ` Paul E. McKenney
2025-03-18 13:24 ` Shrikanth Hegde
2025-03-18 16:12 ` Davidlohr Bueso
2025-03-25 19:04 ` Shrikanth Hegde
2025-03-26 9:31 ` Sebastian Andrzej Siewior
2025-03-26 12:54 ` Shrikanth Hegde
2025-03-26 14:01 ` Sebastian Andrzej Siewior
2025-03-26 8:49 ` Sebastian Andrzej Siewior
2025-04-07 16:15 ` Sebastian Andrzej Siewior
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