From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.ilvokhin.com (mail.ilvokhin.com [178.62.254.231]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 69A5E3EB815; Wed, 18 Mar 2026 18:46:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.62.254.231 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773859565; cv=none; b=crw44GMJfGfZqekE/FkS0ZwLLFlpPS7/UXk6G5LHMLA5t0XBiVnv3fulN6abPQPEe/tEWAufPnM6fWyqyIa9yUnwG3o0+pPsuhvJj4bPERxwSsSxw2p4L9D/ZyuoOff04boktlZlx4iw6maYkSo1VoAaDdhHLrFx80k7L1YXFbQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773859565; c=relaxed/simple; bh=69emOaxLpThjC7Yg1cwTWjaOzWxBNYXsb/jzcLhBkR4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=GSRkYz6OYZVOUhmnzGYTxt6nN+agatU1LdaZ7dAMiyaF2ZOsM03OZPB1jb2LJAm2nCtjYAmMD9S9BVkvyGJQHncMUc8APk4u/OSPnAH54A4Bma1zqiilZOupCg7qOMXkKYaQlBaPIUlZilBSs8pJksbmQhn/CN78ysMR+UX1Irc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=ilvokhin.com; spf=pass smtp.mailfrom=ilvokhin.com; dkim=pass (1024-bit key) header.d=ilvokhin.com header.i=@ilvokhin.com header.b=N+hWuJ1A; arc=none smtp.client-ip=178.62.254.231 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=ilvokhin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ilvokhin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ilvokhin.com header.i=@ilvokhin.com header.b="N+hWuJ1A" Received: from localhost.localdomain (shell.ilvokhin.com [138.68.190.75]) (Authenticated sender: d@ilvokhin.com) by mail.ilvokhin.com (Postfix) with ESMTPSA id 8C128B3E3C; Wed, 18 Mar 2026 18:45:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ilvokhin.com; s=mail; t=1773859553; bh=ezdQ/F1a9PQHRulpi8cke6vRgjLP5GH76Dfq640SPO0=; h=From:To:Cc:Subject:Date; b=N+hWuJ1Aufm8nD8KZtt4ROPvMhpSNIEkP0Wuc0uMViH2juxUYlJhklH8g6KfKRHgE W/j/HPfNThDJweibRwtpH8yaOncNtCRkYmnMNQHg2or7mCFkfzxSdvNNINJXo89LXb KOsHJPi4YlfbnZN4cT5x8v6+YB2WH1bBjr7YrXSc= From: Dmitry Ilvokhin To: Arnd Bergmann , Dennis Zhou , Tejun Heo , Christoph Lameter , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com, Dmitry Ilvokhin Subject: [PATCH v3 0/4] locking: contended_release tracepoint instrumentation Date: Wed, 18 Mar 2026 18:45:17 +0000 Message-ID: X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The existing contention_begin/contention_end tracepoints fire on the waiter side. The lock holder's identity and stack can be captured at contention_begin time (e.g. perf lock contention --lock-owner), but this reflects the holder's state when a waiter arrives, not when the lock is actually released. This series adds a contended_release tracepoint that fires on the holder side when a lock with waiters is released. This provides: - Hold time estimation: when the holder's own acquisition was contended, its contention_end (acquisition) and contended_release can be correlated to measure how long the lock was held under contention. - The holder's stack at release time, which may differ from what perf lock contention --lock-owner captures if the holder does significant work between the waiter's arrival and the unlock. The series is structured as follows: 1. Remove unnecessary linux/sched.h include from trace/events/lock.h. 2. Extract __percpu_up_read() out of the inline percpu_up_read() to avoid binary size increase from adding a tracepoint. 3. Add contended_release tracepoint and instrument sleepable locks: mutex, rtmutex, semaphore, rwsem, percpu-rwsem, and rwbase_rt. 4. RFC. Extend contended_release to queued spinlocks and queued rwlocks. v2 -> v3: - Added new patch: extend contended_release tracepoint to queued spinlocks and queued rwlocks (marked as RFC, requesting feedback). This is prompted by Matthew Wilcox's suggestion to try to come up with generic instrumentation, instead of instrumenting each "special" lock manually. See [1] for the discussion. - Reworked tracepoint placement to fire before the lock is released and before the waiter is woken where possible, for consistency with spinning locks where there is no explicit wake (inspired by Usama Arif's suggestion). - Remove unnecessary linux/sched.h include from trace/events/lock.h. RFC -> v2: - Add trace_contended_release_enabled() guard before waiter checks that exist only for the tracepoint (Steven Rostedt). - Rename __percpu_up_read_slowpath() to __percpu_up_read() (Peter Zijlstra). - Add extern for __percpu_up_read() (Peter Zijlstra). - Squashed tracepoint introduction and usage commits (Masami Hiramatsu). v2: https://lore.kernel.org/all/cover.1773164180.git.d@ilvokhin.com/ RFC: https://lore.kernel.org/all/cover.1772642407.git.d@ilvokhin.com/ [1]: https://lore.kernel.org/all/aa7G1nD7Rd9F4eBH@casper.infradead.org/ Dmitry Ilvokhin (4): tracing/lock: Remove unnecessary linux/sched.h include locking/percpu-rwsem: Extract __percpu_up_read() locking: Add contended_release tracepoint to sleepable locks locking: Add contended_release tracepoint to spinning locks include/asm-generic/qrwlock.h | 48 +++++++++++++++++++++++++++------ include/asm-generic/qspinlock.h | 25 +++++++++++++++-- include/linux/percpu-rwsem.h | 15 +++-------- include/trace/events/lock.h | 18 ++++++++++++- kernel/locking/mutex.c | 3 +++ kernel/locking/percpu-rwsem.c | 22 +++++++++++++++ kernel/locking/qrwlock.c | 16 +++++++++++ kernel/locking/qspinlock.c | 8 ++++++ kernel/locking/rtmutex.c | 1 + kernel/locking/rwbase_rt.c | 8 +++++- kernel/locking/rwsem.c | 9 +++++-- kernel/locking/semaphore.c | 4 ++- 12 files changed, 150 insertions(+), 27 deletions(-) -- 2.52.0