linux-kernel - [PATCH v2 0/8] locking/rwsem: Rework writer wakeup and handoff

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Message-Id: <20230327202413.1955856-1-longman@redhat.com>
Date:   Mon, 27 Mar 2023 16:24:05 -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, Waiman Long <longman@...hat.com>
Subject: [PATCH v2 0/8] locking/rwsem: Rework writer wakeup and handoff

This is a followup to the patches in queue.git locking/core branch
posted by Peter in [1]. His patch series unified the reader and writer
paths as much as possible and making the code a bit easier to maintain.
Unfortunately, it did regress performance because it suppress writer
lock stealing via optimistic spinning [2].

This series include the 7 patches in his locking/core branch with a minor
change to the last one to remove the now unneeded rwsem_wlock_ehandoff
event. The last patch in the series restores the old write lock slow
path behavior of acquiring the write lock mostly in the slow path which
is necessary to restore the performance level back to parity.

[1] https://lore.kernel.org/lkml/Y%2FuN+89FlTw45uiA@hirez.programming.kicks-ass.net/
[2] https://lore.kernel.org/lkml/c126f079-88a2-4067-6f94-82f51cf5ff2b@redhat.com/

Peter Zijlstra (6):
  locking/rwsem: Enforce queueing when HANDOFF
  locking/rwsem: Rework writer wakeup
  locking/rwsem: Simplify rwsem_writer_wake()
  locking/rwsem: Split out rwsem_reader_wake()
  locking/rwsem: Unify wait loop
  locking/rwsem: Use the force

Waiman Long (2):
  locking/rwsem: Minor code refactoring in rwsem_mark_wake()
  locking/rwsem: Restore old write lock slow path behavior

 kernel/locking/rwsem.c | 466 ++++++++++++++++++++++-------------------
 1 file changed, 246 insertions(+), 220 deletions(-)

-- 
2.31.1