From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CF42C109B46D for ; Tue, 31 Mar 2026 14:11:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 43D2A6B0095; Tue, 31 Mar 2026 10:11:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 415376B0096; Tue, 31 Mar 2026 10:11:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 351E16B0098; Tue, 31 Mar 2026 10:11:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 295F06B0095 for ; Tue, 31 Mar 2026 10:11:56 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id DB841E0261 for ; Tue, 31 Mar 2026 14:11:55 +0000 (UTC) X-FDA: 84606546990.13.B00B7A3 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) by imf13.hostedemail.com (Postfix) with ESMTP id CAB7520009 for ; Tue, 31 Mar 2026 14:11:53 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=jeSL2mHH; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf13.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.181 as permitted sender) smtp.mailfrom=usama.arif@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774966314; h=from:from:sender: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:dkim-signature; bh=TdPxN9QaNf36x/V2Ie3LXQAiv3fTO3U7y0mPTWEOTDE=; b=UxoYLfiAQ3KLCRl9EvcPHKj09AeZB87+PReshx55eYOB0xqphRgeuzBWrjTKF6hkoSeobL TOGPpAxoEv+6wT8N8+CiJYwxCwtKy6KXuIPwvAWPNndR3Y0NXwIYo18TWJfSP7iDc+LPJo XVobItMPrNHn4shmKpKVnmOcJjVi0Bc= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774966314; a=rsa-sha256; cv=none; b=u/wN2uYNFaOD/XbYBpMSOs25a3TOChXPxza/W0xYTlG2bMKHg/QdSGQktwn+P0O1jat0iF EJvmqa9ZtS4nFg8DPtRjrs2tuz2RJhDD63vCVtCt0jC5GSXtnx0RJXXuVBRptEe2M1qOjS AMWrg0JS3E0T7HtVGsaba85eCYMIaPU= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=jeSL2mHH; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf13.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.181 as permitted sender) smtp.mailfrom=usama.arif@linux.dev 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 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 X-Rspamd-Queue-Id: CAB7520009 X-Stat-Signature: 1pijy8pmtngejz3acjx67ag5srzzbn1t X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1774966313-699199 X-HE-Meta: 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 g8VDZSRu ZVZ6CY0PMzetWE7Uk1vYlmDZgfQ3X48698RjcR6Fgc0+Rngimi0m9Vq09lWJ9KqlFUZCPp9jzHIKUktfQlCMYUV3hsZUnrvaYb0OpgEN89pgWk2mCNTm9KHkrXkPv56A5zcUzx2t6HQtQoecW45mlUsCypRuUIZsZ8W5iQ5UHWcZazp+HX514vrYFZJerlDiefoSpLuA9N+7UIjCuNzbOj+Oe7umyPFzOJHytMEOQ7VJEyxzc2bXVAOwkGwhDjpPiebAM0FpG1QAhSASiZWRd4vNI4GLLoKdZqP6muRUEdlCVsAK2WvbMxKKVrMXQDCrVQw8x Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.