From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (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 227DC3E9282 for ; Tue, 31 Mar 2026 14:12:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774966323; cv=none; b=e06kKLB1yxFUqOSlFd9hKRdbZJz1qpozpwkoUR0irdF1gCN7r3ge3t3kY6/+exYXsw7/aB1W0DwsfHkWvNaYqZDGYf0nhO2VzXNsUprjxA4848Z+zWPWbcgdoLYje5op/zPd+IJj7luD+PliNLZRExQMgD6EceIZHwV9FJwxvE0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774966323; c=relaxed/simple; bh=SEFtJVL8+fOnpDt6n+BLZJiIueQF4OjMlbAULfzAbiE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Wl9UuW9cnOGHhw1yWFJnJRteS8nhF0odMtXfNwqLHiJqzJUeZ/8hbm62Spe/PfB2WRRT985hB3vG67gzktwrssYkxYQkGpPFRNw35A9ZLVucldud6A/iQnpVq8lSL8h1L17N5DO01vNhv2SLlehnG7iREugtHJTpgr6Uh3J2iLU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=jeSL2mHH; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="jeSL2mHH" Message-ID: <157dc048-4b2f-4170-b9ed-a72f5599e460@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774966309; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TdPxN9QaNf36x/V2Ie3LXQAiv3fTO3U7y0mPTWEOTDE=; b=jeSL2mHHnGMx63cxD4zvGwxlACLsVsl7hBb6An0yUyWU4Keh1E51CS0u318GzzMGMiEsRG uYkNEF5p9F59Ki2EdLT+y7fWRrnDmJjgI3VFCB+QP786AS6D1cxHmuDUvO9KE9wZof7vPe 8vNKYD8P0hSJBsNkzW8Q2/LDRkXOY6E= Date: Tue, 31 Mar 2026 15:11:15 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v4 3/5] locking: Add contended_release tracepoint to sleepable locks Content-Language: en-GB To: Dmitry Ilvokhin Cc: 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 References: <20260331103451.1070175-1-usama.arif@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 31/03/2026 15:16, Dmitry Ilvokhin wrote: > On Tue, Mar 31, 2026 at 03:34:50AM -0700, Usama Arif wrote: >> 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. >> > > Thanks for the feedback, Usama. > > waiter is declared at function scope, right on top. It's also assigned > before the if block, so it's still in scope at the tracepoint. Ah ok, I was reviewing on top of mm-new branch from today where waiter is declared in the if block. Probably something changed related to locking/tracing and its not in mm-new yet.