From nobody Mon Apr 6 18:24:00 2026 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 7EC2A3EB7E1; Wed, 18 Mar 2026 18:46:02 +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=oxP2rBCepkqwOXvOtvzEhS96G8kJ+oojVuECxTVWAUD+4dTpb9SfpjVcTcLKat097XI8mXSY8IEZhw9Kuj/ATL4d0bEp+bXRgMupTGoa6xUj+RFPL9pjIOkOCzdGVcrxiv5JrYUsSyy7q4EiTxGTkvbyfRnT0sRWG4pNuDm0fiI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773859565; c=relaxed/simple; bh=ofaVDvAA6+obzoQASneuh29HlFvYu/NEOKGouykxSrw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JtCvRfiHT6xeny1KwmjdK7Kw6hr/47VQEDhQ0ZPQQVHqjU/RVpgyTq44c/ZaaXZCmo/Yv8/kED8mJyh+Oo0jC+58tAjImdwdxVX8xVliiAPFzAz+eEs2rl/NE2wwuxXUSHW8Y2zuETr/9oecLSNf0xpnvZHrEcky2nl11LKuVJU= 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=heHA5Omz; 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="heHA5Omz" Received: from localhost.localdomain (shell.ilvokhin.com [138.68.190.75]) (Authenticated sender: d@ilvokhin.com) by mail.ilvokhin.com (Postfix) with ESMTPSA id 716FBB3E46; Wed, 18 Mar 2026 18:45:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ilvokhin.com; s=mail; t=1773859554; bh=dii3j/x0ZzJ6zru2y3vbKrgi3XfTdpsXr7lgtGyp114=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=heHA5OmzNR4pBVCQiXiVwD2U7LO9WNFnY2iIiTS5t3QiuidYpa6PFOuATAY+5ZErf TH/5gr0/YZ3igy2prDaonM5b0M78LMZ9Zk2sQU44n0nmEI5EY3iH5HOgHjxp8CBdSM DHoHpvpOvXw5pSjDAffSKSL9e6bYkv81XX6Oi60s= 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 3/4] locking: Add contended_release tracepoint to sleepable locks Date: Wed, 18 Mar 2026 18:45:20 +0000 Message-ID: <8579f5a43624ffddfe9a5dcc4b1fa59f016a4c75.1773858853.git.d@ilvokhin.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add the contended_release trace event. This tracepoint fires on the holder side when a contended lock is released, complementing the existing contention_begin/contention_end tracepoints which fire on the waiter side. This enables correlating lock hold time under contention with waiter events by lock address. Add trace_contended_release() calls to the slowpath unlock paths of sleepable locks: mutex, rtmutex, semaphore, rwsem, percpu-rwsem, and RT-specific rwbase locks. Where possible, trace_contended_release() fires before the lock is released and before the waiter is woken. For rwsem, semaphore, and rwbase_rt read unlock, the tracepoint fires after the release but before the wake, as contention is determined by the return value of the atomic release operation. Signed-off-by: Dmitry Ilvokhin --- include/trace/events/lock.h | 17 +++++++++++++++++ kernel/locking/mutex.c | 3 +++ kernel/locking/percpu-rwsem.c | 4 ++++ kernel/locking/rtmutex.c | 1 + kernel/locking/rwbase_rt.c | 8 +++++++- kernel/locking/rwsem.c | 9 +++++++-- kernel/locking/semaphore.c | 4 +++- 7 files changed, 42 insertions(+), 4 deletions(-) diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h index da978f2afb45..1ded869cd619 100644 --- a/include/trace/events/lock.h +++ b/include/trace/events/lock.h @@ -137,6 +137,23 @@ TRACE_EVENT(contention_end, TP_printk("%p (ret=3D%d)", __entry->lock_addr, __entry->ret) ); =20 +TRACE_EVENT(contended_release, + + TP_PROTO(void *lock), + + TP_ARGS(lock), + + TP_STRUCT__entry( + __field(void *, lock_addr) + ), + + TP_fast_assign( + __entry->lock_addr =3D lock; + ), + + TP_printk("%p", __entry->lock_addr) +); + #endif /* _TRACE_LOCK_H */ =20 /* This part must be outside protection */ diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 427187ff02db..bb25741c2768 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -997,6 +997,9 @@ static noinline void __sched __mutex_unlock_slowpath(st= ruct mutex *lock, unsigne wake_q_add(&wake_q, next); } =20 + if (trace_contended_release_enabled() && waiter) + trace_contended_release(lock); + if (owner & MUTEX_FLAG_HANDOFF) __mutex_handoff(lock, next); =20 diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index f3ee7a0d6047..6bf2ccddd42d 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -263,6 +263,9 @@ void percpu_up_write(struct percpu_rw_semaphore *sem) { rwsem_release(&sem->dep_map, _RET_IP_); =20 + if (trace_contended_release_enabled() && wq_has_sleeper(&sem->waiters)) + trace_contended_release(sem); + /* * Signal the writer is done, no fast path yet. * @@ -292,6 +295,7 @@ EXPORT_SYMBOL_GPL(percpu_up_write); void __percpu_up_read(struct percpu_rw_semaphore *sem) { lockdep_assert_preemption_disabled(); + trace_contended_release(sem); /* * slowpath; reader will only ever wake a single blocked * writer. diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index ccaba6148b61..3db8a840b4e8 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1466,6 +1466,7 @@ static void __sched rt_mutex_slowunlock(struct rt_mut= ex_base *lock) raw_spin_lock_irqsave(&lock->wait_lock, flags); } =20 + trace_contended_release(lock); /* * The wakeup next waiter path does not suffer from the above * race. See the comments there. diff --git a/kernel/locking/rwbase_rt.c b/kernel/locking/rwbase_rt.c index 82e078c0665a..081778934b13 100644 --- a/kernel/locking/rwbase_rt.c +++ b/kernel/locking/rwbase_rt.c @@ -162,8 +162,10 @@ static void __sched __rwbase_read_unlock(struct rwbase= _rt *rwb, * worst case which can happen is a spurious wakeup. */ owner =3D rt_mutex_owner(rtm); - if (owner) + if (owner) { + trace_contended_release(rwb); rt_mutex_wake_q_add_task(&wqh, owner, state); + } =20 /* Pairs with the preempt_enable in rt_mutex_wake_up_q() */ preempt_disable(); @@ -205,6 +207,8 @@ static inline void rwbase_write_unlock(struct rwbase_rt= *rwb) unsigned long flags; =20 raw_spin_lock_irqsave(&rtm->wait_lock, flags); + if (trace_contended_release_enabled() && rt_mutex_has_waiters(rtm)) + trace_contended_release(rwb); __rwbase_write_unlock(rwb, WRITER_BIAS, flags); } =20 @@ -214,6 +218,8 @@ static inline void rwbase_write_downgrade(struct rwbase= _rt *rwb) unsigned long flags; =20 raw_spin_lock_irqsave(&rtm->wait_lock, flags); + if (trace_contended_release_enabled() && rt_mutex_has_waiters(rtm)) + trace_contended_release(rwb); /* Release it and account current as reader */ __rwbase_write_unlock(rwb, WRITER_BIAS - 1, flags); } diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index bf647097369c..767a1a2b7d8c 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1390,6 +1390,7 @@ static inline void __up_read(struct rw_semaphore *sem) if (unlikely((tmp & (RWSEM_LOCK_MASK|RWSEM_FLAG_WAITERS)) =3D=3D RWSEM_FLAG_WAITERS)) { clear_nonspinnable(sem); + trace_contended_release(sem); rwsem_wake(sem); } preempt_enable(); @@ -1413,8 +1414,10 @@ static inline void __up_write(struct rw_semaphore *s= em) preempt_disable(); rwsem_clear_owner(sem); tmp =3D atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count); - if (unlikely(tmp & RWSEM_FLAG_WAITERS)) + if (unlikely(tmp & RWSEM_FLAG_WAITERS)) { + trace_contended_release(sem); rwsem_wake(sem); + } preempt_enable(); } =20 @@ -1437,8 +1440,10 @@ static inline void __downgrade_write(struct rw_semap= hore *sem) tmp =3D atomic_long_fetch_add_release( -RWSEM_WRITER_LOCKED+RWSEM_READER_BIAS, &sem->count); rwsem_set_reader_owned(sem); - if (tmp & RWSEM_FLAG_WAITERS) + if (tmp & RWSEM_FLAG_WAITERS) { + trace_contended_release(sem); rwsem_downgrade_wake(sem); + } preempt_enable(); } =20 diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c index 74d41433ba13..d46415095dd6 100644 --- a/kernel/locking/semaphore.c +++ b/kernel/locking/semaphore.c @@ -231,8 +231,10 @@ void __sched up(struct semaphore *sem) else __up(sem, &wake_q); raw_spin_unlock_irqrestore(&sem->lock, flags); - if (!wake_q_empty(&wake_q)) + if (!wake_q_empty(&wake_q)) { + trace_contended_release(sem); wake_up_q(&wake_q); + } } EXPORT_SYMBOL(up); =20 --=20 2.52.0