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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-485885bbb51sm27883762f8f.30.2026.09.07.01.41.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Sep 2026 01:41:45 -0700 (PDT) From: David Laight To: Waiman Long , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , linux-kernel@vger.kernel.org, Linus Torvalds , Yafang Shao , Steven Rostedt Cc: David Laight Subject: [PATCH v4 next 0/9] locking/osq_lock: Optimisations to osq_lock code Date: Mon, 7 Sep 2026 09:41:24 +0100 Message-Id: <20260907084133.3696-1-david.laight.linux@gmail.com> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This is a continuation of some patches I wrote over two years ago. They go a lot further and reduce the per-cpu data to a structure that only contains two cpu numbers. I've fixed some broken/missing memory barriers but left the initial xchg() when acquiring the lock as a full barrier, I think it could be relaxed. Tested with a userspace harness that can conditionally sleep at various points. David Laight (9): locking/osq_lock: Add some comments about how it works locking/osq_lock: Save the cpu number for 'prev' not the node address locking/osq_lock: Set prev_cpu=0 instead of locked=1 locking/osq_lock: Delete 'fast path' code from osq_unlock() locking/osq_lock: Avoid writing to node->next in the osq_lock() fast path locking/osq: Use cpu number for 'next' pointer locking/osq: Use 'unsigned int' for next/prev/tail locking/osq: inline encode_cpu() and rename decode_cpu() locking/osq_lock: Swap next<->prev and tail<->head include/linux/osq_lock.h | 10 +- kernel/locking/osq_lock.c | 286 ++++++++++++++++++++------------------ 2 files changed, 154 insertions(+), 142 deletions(-) -- 2.39.5