linux-kernel - [PATCH v2 0/2] locking/rwsem: Fix rwsem waiter optimistic spinning problem with RT tasks

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Message-Id: <20221012133333.1265281-1-longman@redhat.com>
Date:   Wed, 12 Oct 2022 09:33:31 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>
Cc:     linux-kernel@...r.kernel.org, john.p.donnelly@...cle.com,
        Hillf Danton <hdanton@...a.com>,
        Mukesh Ojha <quic_mojha@...cinc.com>,
        Ting11 Wang 王婷 
        <wangting11@...omi.com>, Waiman Long <longman@...hat.com>
Subject: [PATCH v2 0/2] locking/rwsem: Fix rwsem waiter optimistic spinning problem with RT tasks

v2:
 - Add an additional patch to limit the # of first waiter optimistic
   spinning in the writer slowpath.

It turns out the current waiter optimistic spinning code does not work
that well if we have RT tasks in the mix. This patch series include
two different fixes to resolve those issues.

Waiman Long (2):
  locking/rwsem: Prevent non-first waiter from spinning in down_write()
    slowpath
  locking/rwsem: Limit # of null owner retries for handoff writer

 kernel/locking/rwsem.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

-- 
2.31.1