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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774953301; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eGoJpSFt6qPU5Tj1tCTJazBok4fp1H7/lxXOEKF1LAE=; b=p33ibMJltLANQa/bsMRalz0WLn9BlHm8C+vEC5ite7qjEZ0cbDSZL23LJhIXOh4mWTMMG4 TBKLq9j8Mz6GbrKJDMbOx9Su5uRTDWM/gjU81JtLwKyzFf6t4mVUaxKYeCN9VzzuGjwlZt rIOn5+Mdz2haHATDFp1JJcwSMAvzAHM= From: Usama Arif To: Dmitry Ilvokhin Cc: Usama Arif , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Thomas Bogendoerfer , Juergen Gross , Ajay Kaher , Alexey Makhalov , Broadcom internal kernel review list , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Dennis Zhou , Tejun Heo , Christoph Lameter , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, virtualization@lists.linux.dev, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v4 3/5] locking: Add contended_release tracepoint to sleepable locks Date: Tue, 31 Mar 2026 03:34:50 -0700 Message-ID: <20260331103451.1070175-1-usama.arif@linux.dev> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Stat-Signature: 6thyn1newxnz974k37ki6ujuu1dhfxs8 X-Rspamd-Queue-Id: 93E8720013 X-Rspam-User: X-HE-Tag: 1774953303-652485 X-HE-Meta: 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 Mg8yY1+F ita/ZHI6h67apkcPpg/07/4WZRIMb3C1zxDhUxvBOchq26nKTZOZfvZMJsl7IseKnKWQSFL7wwtr8e5wlw8mIg2GWNhdk86CuJs3oXxJd+yLeY1x0eflNFjGbwEFlZa/GtVw3LnvW+NOBSM1ZZCsLEzlmfddEGc6eZg0oHaBVIw7qfkra65HA79DexurCQMo7fz7x9E5VDDgGOI60+R9h2czCTTkPfY02vKpZvzyYYF/suTBvnigqrkFCEJ2NJX0hmfdjCs7aTSi3ilz2Wzq8UHRY3V1dV9s/PBnf5c2pA8ClQ+t4+lS9zf16VA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 26 Mar 2026 15:10:02 +0000 Dmitry Ilvokhin wrote: > 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 some lock types, the > tracepoint fires after the release but before the wake. Making the > placement consistent across all lock types is not worth the added > complexity. > > For reader/writer locks, the tracepoint fires for every reader releasing > while a writer is waiting, not only for the last reader. > > Signed-off-by: Dmitry Ilvokhin > --- > include/trace/events/lock.h | 17 +++++++++++++++++ > kernel/locking/mutex.c | 4 ++++ > kernel/locking/percpu-rwsem.c | 11 +++++++++++ > kernel/locking/rtmutex.c | 1 + > kernel/locking/rwbase_rt.c | 6 ++++++ > kernel/locking/rwsem.c | 10 ++++++++-- > kernel/locking/semaphore.c | 4 ++++ > 7 files changed, 51 insertions(+), 2 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=%d)", __entry->lock_addr, __entry->ret) > ); > > +TRACE_EVENT(contended_release, > + > + TP_PROTO(void *lock), > + > + TP_ARGS(lock), > + > + TP_STRUCT__entry( > + __field(void *, lock_addr) > + ), > + > + TP_fast_assign( > + __entry->lock_addr = lock; > + ), > + > + TP_printk("%p", __entry->lock_addr) > +); > + > #endif /* _TRACE_LOCK_H */ > > /* This part must be outside protection */ > diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c > index 427187ff02db..6c2c9312eb8f 100644 > --- a/kernel/locking/mutex.c > +++ b/kernel/locking/mutex.c > @@ -997,6 +997,9 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne > wake_q_add(&wake_q, next); > } > > + if (trace_contended_release_enabled() && waiter) > + trace_contended_release(lock); > + This won't compile? waiter is declared in the if block, so you are using it outside scope here.