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From: "tip-bot2 for Waiman Long" <tip-bot2@linutronix.de>
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Reply-to: linux-kernel@vger.kernel.org
To: linux-tip-commits@vger.kernel.org
Subject: [tip: locking/core] locking/rwsem: Clarify that RWSEM_READER_OWNED is
just a hint
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>, x86@kernel.org,
linux-kernel@vger.kernel.org
In-Reply-To: <20240222150540.79981-4-longman@redhat.com>
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[tip:,locking/core] locking/rwsem: Clarify that RWSEM_READER_OWNED is just a hint
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Commit Message
tip-bot2 for Thomas Gleixner
Feb. 28, 2024, 12:53 p.m. UTC
The following commit has been merged into the locking/core branch of tip: Commit-ID: d566c78659eccf085f905fd266fc461de92eaa8f Gitweb: https://git.kernel.org/tip/d566c78659eccf085f905fd266fc461de92eaa8f Author: Waiman Long <longman@redhat.com> AuthorDate: Thu, 22 Feb 2024 10:05:39 -05:00 Committer: Ingo Molnar <mingo@kernel.org> CommitterDate: Wed, 28 Feb 2024 13:08:38 +01:00 locking/rwsem: Clarify that RWSEM_READER_OWNED is just a hint Clarify in the comments that the RWSEM_READER_OWNED bit in the owner field is just a hint, not an authoritative state of the rwsem. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Link: https://lore.kernel.org/r/20240222150540.79981-4-longman@redhat.com --- kernel/locking/rwsem.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 2340b6d..c6d17ae 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -35,7 +35,7 @@ /* * The least significant 2 bits of the owner value has the following * meanings when set. - * - Bit 0: RWSEM_READER_OWNED - The rwsem is owned by readers + * - Bit 0: RWSEM_READER_OWNED - rwsem may be owned by readers (just a hint) * - Bit 1: RWSEM_NONSPINNABLE - Cannot spin on a reader-owned lock * * When the rwsem is reader-owned and a spinning writer has timed out, @@ -1002,8 +1002,8 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat /* * To prevent a constant stream of readers from starving a sleeping - * waiter, don't attempt optimistic lock stealing if the lock is - * currently owned by readers. + * writer, don't attempt optimistic lock stealing if the lock is + * very likely owned by readers. */ if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) && (rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))