From: Waiman Long <longman@redhat.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] locking/rwsem: Wake up all readers for wait queue waker
Date: Thu, 16 Feb 2023 16:07:25 -0500 [thread overview]
Message-ID: <0baab14d-abea-4248-e6d5-23c465f0a4a5@redhat.com> (raw)
In-Reply-To: <20230214030901.3250-1-hdanton@sina.com>
On 2/13/23 22:09, Hillf Danton wrote:
> On Mon, 13 Feb 2023 14:48:32 -0500 Waiman Long <longman@redhat.com>
>>
>> @@ -1281,7 +1282,7 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
>> raw_spin_lock_irqsave(&sem->wait_lock, flags);
>>
>> if (!list_empty(&sem->wait_list))
>> - rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED, &wake_q);
>> + rwsem_mark_wake(sem, RWSEM_WAKE_READ_OWNED, &wake_q, false);
>>
>> raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
>> wake_up_q(&wake_q);
>> --
>> 2.31.1
> Downgrade is conceptually the right time to let all read waiters go
> regardless write waiter.
Still, a downgraded task is still in the read critical section and we
shouldn't introduce arbitrary latency to that. Let's focus on the easy
one and we can discuss about other possibility later.
Thanks,
Longman
prev parent reply other threads:[~2023-02-16 21:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-13 19:48 [PATCH-tip 0/2] locking/rwsem: Miscellaneous rwsem enhancements Waiman Long
2023-02-13 19:48 ` [PATCH 1/2] locking/rwsem: Enable early rwsem writer lock handoff Waiman Long
2023-02-13 19:48 ` [PATCH 2/2] locking/rwsem: Wake up all readers for wait queue waker Waiman Long
[not found] ` <20230214030901.3250-1-hdanton@sina.com>
2023-02-16 21:07 ` Waiman Long [this message]
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