From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 011.lax.mailroute.net (011.lax.mailroute.net [199.89.1.14]) (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 311B33A7F4D for ; Mon, 4 May 2026 11:56:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=199.89.1.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777895784; cv=none; b=a6rH2inSAgqHv5BENdEYloYK/RcO+G+dFvvkXt1BJwJU5VmDQOjUtWz5xkHFJSMINXzM9uxVJzz5QNkG6ouC3mXWBXB95Nb/XHRJRCi4QO814IgdhaYyJpbglv4es/Jq6x/06sSPj8evAaSes+hBHyyy+e7gSpIJ2G28cQOzSZE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777895784; c=relaxed/simple; bh=XA8cx77wh3EGH7UikcnYxk/f+j2dQ9+c8XZ2T/hOIa8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IHlXrwzTqAYnDj3kmP6MkQgBaPSfa7wPig73REbAw40RQnzZNc7V+1/4+S7SRA8hISSkBuJbUxgIScQrxnwOlGcEGatURjExBFjpn2P5YGSNMUhzyPi+Fc65dqeOTl+uaFrdJzDJwAjHlhYkIGa575I36ZFEgYRhn5k/QUqVymk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org; spf=pass smtp.mailfrom=acm.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b=fJEmwrnv; arc=none smtp.client-ip=199.89.1.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=acm.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=acm.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=acm.org header.i=@acm.org header.b="fJEmwrnv" Received: from localhost (localhost [127.0.0.1]) by 011.lax.mailroute.net (Postfix) with ESMTP id 4g8KqV47YLz1XM6Jb; Mon, 4 May 2026 11:56:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=acm.org; h= content-transfer-encoding:content-type:content-type:in-reply-to :from:from:content-language:references:subject:subject :user-agent:mime-version:date:date:message-id:received:received; s=mr01; t=1777895771; x=1780487772; bh=O90JTdZHsCJTEUFIAcJ7cZdc LDqCIVmYhvNUPQqL3SM=; b=fJEmwrnvhWzIjfepjxZNSRxIVi/60EyYXOprVbm0 gwFCT2B7bZm0qXtD6Cp9/wHprdZivOsABW2XgO9YX0UJwnhWoO1XrGPN/xhs74lF R9whLSPeys3s0D2HHrj0N8q9oPuZnlgPRBLGEqW7IpsaokMyMpNIWarZPC/xjjb8 5TeHrAZRLHRzGkMQug+NWqrc/aVzaMxBwLT9cvzGUH8Ei1XgIsm+fwcj/i4zi3gK HkVUGBcMY8Hq34Gp5xlo427T5zV/PXYKhbwB6wRT6AcQbILiNyuOMkWl8MzBqNDI twfIN0mgmIFJIIArJCe4FqTJSwErdZ+XdftSsDBVNupLaA== X-Virus-Scanned: by MailRoute Received: from 011.lax.mailroute.net ([127.0.0.1]) by localhost (011.lax [127.0.0.1]) (mroute_mailscanner, port 10029) with LMTP id 1kTVc5ONpvsM; Mon, 4 May 2026 11:56:11 +0000 (UTC) Received: from [10.211.8.56] (unknown [213.147.98.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bvanassche@acm.org) by 011.lax.mailroute.net (Postfix) with ESMTPSA id 4g8KqC4W5vz1XM5kD; Mon, 4 May 2026 11:56:06 +0000 (UTC) Message-ID: <7682dc25-2bd5-46c0-883a-594fcf39893e@acm.org> Date: Mon, 4 May 2026 13:56:03 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] locking/rtmutex: Annotate API and implementation To: Peter Zijlstra Cc: Marco Elver , linux-kernel@vger.kernel.org, Ingo Molnar , Will Deacon , Boqun Feng , Joel Granados , Alexei Starovoitov , Sebastian Andrzej Siewior , Vlastimil Babka References: <20260502015354.430273-1-bvanassche@acm.org> <20260504093932.GR3126523@noisy.programming.kicks-ass.net> Content-Language: en-US From: Bart Van Assche In-Reply-To: <20260504093932.GR3126523@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/4/26 11:39 AM, Peter Zijlstra wrote: > This does not build, I need at least the below, but then PREEMPT_RT is > still not happy. Apparently I had tested my patch with PREEMPT_RT=n only. The patch below should support both PREEMPT_RT=n and PREEMPT_RT=y: --- include/linux/rtmutex.h | 22 +++++++++++++++------- kernel/locking/Makefile | 1 + kernel/locking/rtmutex.c | 5 +++++ kernel/locking/rtmutex_api.c | 6 ++++++ 4 files changed, 27 insertions(+), 7 deletions(-) diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h index 78e7e588817c..9e1f012f89db 100644 --- a/include/linux/rtmutex.h +++ b/include/linux/rtmutex.h @@ -56,6 +56,8 @@ static inline struct task_struct *rt_mutex_owner(struct rt_mutex_base *lock) #endif extern void rt_mutex_base_init(struct rt_mutex_base *rtb); +context_lock_struct(rt_mutex); + /** * The rt_mutex structure * @@ -108,8 +110,10 @@ do { \ extern void __rt_mutex_init(struct rt_mutex *lock, const char *name, struct lock_class_key *key); #ifdef CONFIG_DEBUG_LOCK_ALLOC -extern void rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass); -extern void _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock); +extern void rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass) + __acquires(lock); +extern void _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock) + __acquires(lock); #define rt_mutex_lock(lock) rt_mutex_lock_nested(lock, 0) #define rt_mutex_lock_nest_lock(lock, nest_lock) \ do { \ @@ -118,15 +122,19 @@ extern void _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map * } while (0) #else -extern void rt_mutex_lock(struct rt_mutex *lock); +extern void rt_mutex_lock(struct rt_mutex *lock) __acquires(lock); #define rt_mutex_lock_nested(lock, subclass) rt_mutex_lock(lock) #define rt_mutex_lock_nest_lock(lock, nest_lock) rt_mutex_lock(lock) #endif -extern int rt_mutex_lock_interruptible(struct rt_mutex *lock); -extern int rt_mutex_lock_killable(struct rt_mutex *lock); -extern int rt_mutex_trylock(struct rt_mutex *lock); +extern int rt_mutex_lock_interruptible(struct rt_mutex *lock) + __cond_acquires(0, lock); +extern int rt_mutex_lock_killable(struct rt_mutex *lock) + __cond_acquires(0, lock); +extern int rt_mutex_trylock(struct rt_mutex *lock) + __cond_acquires(true, lock); -extern void rt_mutex_unlock(struct rt_mutex *lock); +extern void rt_mutex_unlock(struct rt_mutex *lock) + __releases(lock); #endif diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile index cee1901d4cff..24dc00e12aa6 100644 --- a/kernel/locking/Makefile +++ b/kernel/locking/Makefile @@ -4,6 +4,7 @@ KCOV_INSTRUMENT := n CONTEXT_ANALYSIS_mutex.o := y +CONTEXT_ANALYSIS_rtmutex.o := y CONTEXT_ANALYSIS_rtmutex_api.o := y CONTEXT_ANALYSIS_ww_rt_mutex.o := y CONTEXT_ANALYSIS_rwsem.o := y diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 4f386ea6c792..69759fde7d10 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -484,6 +484,7 @@ static __always_inline bool __waiter_less(struct rb_node *a, const struct rb_nod static __always_inline void rt_mutex_enqueue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter) + __must_hold(&lock->wait_lock) { lockdep_assert_held(&lock->wait_lock); @@ -492,6 +493,7 @@ rt_mutex_enqueue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter) static __always_inline void rt_mutex_dequeue(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter) + __must_hold(&lock->wait_lock) { lockdep_assert_held(&lock->wait_lock); @@ -1092,6 +1094,7 @@ static int __sched rt_mutex_adjust_prio_chain(struct task_struct *task, static int __sched try_to_take_rt_mutex(struct rt_mutex_base *lock, struct task_struct *task, struct rt_mutex_waiter *waiter) + __must_hold(&lock->wait_lock) { lockdep_assert_held(&lock->wait_lock); @@ -1319,6 +1322,7 @@ static int __sched task_blocks_on_rt_mutex(struct rt_mutex_base *lock, */ static void __sched mark_wakeup_next_waiter(struct rt_wake_q_head *wqh, struct rt_mutex_base *lock) + __must_hold(&lock->wait_lock) { struct rt_mutex_waiter *waiter; @@ -1479,6 +1483,7 @@ static void __sched rt_mutex_slowunlock(struct rt_mutex_base *lock) } static __always_inline void __rt_mutex_unlock(struct rt_mutex_base *lock) + __no_context_analysis { if (likely(rt_mutex_cmpxchg_release(lock, current, NULL))) return; diff --git a/kernel/locking/rtmutex_api.c b/kernel/locking/rtmutex_api.c index 124219aea46e..23ad997ddd65 100644 --- a/kernel/locking/rtmutex_api.c +++ b/kernel/locking/rtmutex_api.c @@ -41,6 +41,7 @@ static __always_inline int __rt_mutex_lock_common(struct rt_mutex *lock, unsigned int state, struct lockdep_map *nest_lock, unsigned int subclass) + __cond_acquires(0, lock) { int ret; @@ -66,12 +67,14 @@ EXPORT_SYMBOL(rt_mutex_base_init); * @subclass: the lockdep subclass */ void __sched rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass) + __no_context_analysis /* ignoring the return value below is fine in this case */ { __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, subclass); } EXPORT_SYMBOL_GPL(rt_mutex_lock_nested); void __sched _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock) + __no_context_analysis /* ignoring the return value below is fine in this case */ { __rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, nest_lock, 0); } @@ -157,6 +160,7 @@ void __sched rt_mutex_unlock(struct rt_mutex *lock) { mutex_release(&lock->dep_map, _RET_IP_); __rt_mutex_unlock(&lock->rtmutex); + __release(lock); } EXPORT_SYMBOL_GPL(rt_mutex_unlock); @@ -182,6 +186,7 @@ int __sched __rt_mutex_futex_trylock(struct rt_mutex_base *lock) */ bool __sched __rt_mutex_futex_unlock(struct rt_mutex_base *lock, struct rt_wake_q_head *wqh) + __must_hold(&lock->wait_lock) { lockdep_assert_held(&lock->wait_lock); @@ -312,6 +317,7 @@ int __sched __rt_mutex_start_proxy_lock(struct rt_mutex_base *lock, struct rt_mutex_waiter *waiter, struct task_struct *task, struct wake_q_head *wake_q) + __must_hold(&lock->wait_lock) { int ret;