linux-kernel - Re: [PATCH 3/5] locking/rwsem: Enable reader optimistic lock stealing

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Message-ID: <20201208035314.rwz72kgn5apr2whm@linux-p48b>
Date:   Mon, 7 Dec 2020 19:53:14 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Waiman Long <longman@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH 3/5] locking/rwsem: Enable reader optimistic lock stealing

On Tue, 17 Nov 2020, Waiman Long wrote:

>If the optimistic spinning queue is empty and the rwsem does not have
>the handoff or write-lock bits set, it is actually not necessary to
>call rwsem_optimistic_spin() to spin on it. Instead, it can steal the
>lock directly as its reader bias is in the count already.  If it is
>the first reader in this state, it will try to wake up other readers
>in the wait queue.
>
>Signed-off-by: Waiman Long <longman@...hat.com>

Reviewed-by: Davidlohr Bueso <dbueso@...e.de>