From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 14BD63E4119 for ; Mon, 12 Oct 2026 10:17:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791800239; cv=none; b=aTE+8MkrIDtC8r6zOnWoOn50cMniyv7rhlLMxqePYZoLnZgyKaqsDyBQ9BkThXn9gbU32REAhaFDMH0L5FAPWJQjWYEurH2hgyLFTwf7y7XZ0/Dz5Ek4mocm1XxS8mW8gTfwQoHyi2k9X4weeCxIsl90EtGFfhKj+n3bkfA/VEw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791800239; c=relaxed/simple; bh=C8b8izUnoFRkEcMLO4tjLqbVdHcgHKlMb2VYt6pTbT0=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=grzBPMSDS/ijllxU+rG0TsUR1cTRbN/R1qj9InoF0yYT0tbUFCPrqHYatxhCKsT0FgHTUfsIE5VTUaavG/NUZOxow4cO9Qbxf9L2SX98AZ0oBdFQh0jasXl+gpTtpQWRvZRbNSu72csFb5zxSRiXtmKeMjOr/iIXTcu2p46qM1o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=oCbNvpnO; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Cvv8X+bg; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="oCbNvpnO"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Cvv8X+bg" Date: Mon, 12 Oct 2026 12:17:04 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1791800226; 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; bh=dvrA4gMuZ9jEM/4kYfdxPGWwHNrPm8/cAG973SsSPrQ=; b=oCbNvpnOPZX0qQbjqNsvh3yo68/sb78ESlhlpvEs8nnLNG4Wn23OOTUlfR1qkDLDSAlqh1 4n7OSAeYsa219dwkoVZ04B/Sc2/fFNlCiHooBfPr0oVk8iQXIxNIPkm0JeoDkZvD3Joawv PJZODrsttVGoRvjQIgeXcie8LWA7qyT0B8bf14EBNQp2VezNkI1FC6qlmMXvPN98JvH1Dz GhTU+BN96bvMpNsD0frdIAxBMdxWnT+j5mfRNXlGq5R0pJDjRjsNWR1icRGKveocujg+VY MxpWglCGBGg4PxO0geqO+oayVin0m8e7qYQFIY0/SKmoaP10JjpHH6DCbRCnIA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1791800226; 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; bh=dvrA4gMuZ9jEM/4kYfdxPGWwHNrPm8/cAG973SsSPrQ=; b=Cvv8X+bgsc9CGwRc9ChlRGF3VEzgP2NODdTKzuHIxJcYXbQgL0nJPdi1zfuTAzhcCQevH+ Qm+aysKHFTMwm9Ag== From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: Ben Segall , Boqun Feng , Clark Williams , David Woodhouse , Dietmar Eggemann , Ingo Molnar , Juri Lelli , K Prateek Nayak , Mel Gorman , Michal Hocko , Peter Zijlstra , Sean Young , Steven Rostedt , Thierry Reding , Valentin Schneider , Vincent Guittot , Waiman Long , Will Deacon Subject: [PATCH v3] sched: Allow sleeping spinlocks on PREEMPT_RT within non_block_start()/end block. Message-ID: <20261012101704.gZyF2O9M@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Commit 312364f3534cc ("kernel.h: Add non_block_start/end()") added non_block_star()/end(). The intention was to catch any callbacks which depend on locks or sleep able conditionals in order to ensure forward progress. According to the commit message spinlocks were excluded "because spinlocks can't have an indirect dependency upon the page allocator=E2=80=A6". On PREEMPT_RT this leads to a splat because spinlock_t and rwlock_t are turned into a sleeping spinlock which have a might_sleep() as they could schedule() on lock contention. Besids mm, the other used of non_block_start() is pwm. Here the hrtimer can acnqure a spinlock_t on RT and I can't tell other user but I assume it is not atomic on RT since it wouldn't be able to acquire its own (spinlock_t) lock. Since spinlock_t (and rwlock_t) are not problem, add a sleeping_lock argument to __might_resched() signaling if this is scheduling request is from a sleeping lock (true) or regular scheduling request (false). Add the `true' argument to rtlock_might_resched() which is used on PREEMPT_RT for both sleeping lock types. Cc: Michal Hocko Cc: David Woodhouse Cc: Sean Young Cc: Thierry Reding Acked-by: David Woodhouse Fixes: 312364f3534c ("kernel.h: Add non_block_start/end()") Reported-by: syzbot+c3178b6b512446632bac@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Dc3178b6b512446632bac Signed-off-by: Sebastian Andrzej Siewior --- v2=E2=80=A6v3: https://lore.kernel.org/all/20260916155105.qDi2MiYW@linutron= ix.de/ - Repost. v1=E2=80=A6v2: https://lore.kernel.org/all/20260821095755.am1-Segb@linutron= ix.de/ - repost with collected tags - Add Reported-by for syzbot include/linux/kernel.h | 5 +++-- include/linux/sched.h | 24 ++++++++++++------------ kernel/locking/spinlock_rt.c | 2 +- kernel/sched/core.c | 7 ++++--- 4 files changed, 20 insertions(+), 18 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 24414c79e59ab..c3937e081f18f 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -70,7 +70,8 @@ extern int dynamic_might_resched(void); #endif /* CONFIG_PREEMPT_* */ =20 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP -extern void __might_resched(const char *file, int line, unsigned int offse= ts); +extern void __might_resched(const char *file, int line, unsigned int offse= ts, + bool rt_sleeping_lock); extern void __might_sleep(const char *file, int line); extern void __cant_sleep(const char *file, int line); extern void __cant_migrate(const char *file, int line); @@ -128,7 +129,7 @@ extern void __cant_migrate(const char *file, int line); # define non_block_end() WARN_ON(current->non_block_count-- =3D=3D 0) #else static inline void __might_resched(const char *file, int line, - unsigned int offsets) { } + unsigned int offsets, bool rt_sleeping_lock) { } static inline void __might_sleep(const char *file, int line) { } # define might_sleep() do { might_resched(); } while (0) # define cant_sleep() do { } while (0) diff --git a/include/linux/sched.h b/include/linux/sched.h index d35ae49a991f7..b758476cf8ae3 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2174,9 +2174,9 @@ static inline int _cond_resched(void) =20 #endif /* !CONFIG_PREEMPTION || CONFIG_PREEMPT_DYNAMIC */ =20 -#define cond_resched() ({ \ - __might_resched(__FILE__, __LINE__, 0); \ - _cond_resched(); \ +#define cond_resched() ({ \ + __might_resched(__FILE__, __LINE__, 0, false); \ + _cond_resched(); \ }) =20 extern int __cond_resched_lock(spinlock_t *lock) __must_hold(lock); @@ -2202,19 +2202,19 @@ extern int __cond_resched_rwlock_write(rwlock_t *lo= ck) __must_hold(lock); (PREEMPT_LOCK_OFFSET + (1U << MIGHT_RESCHED_RCU_SHIFT)) #endif =20 -#define cond_resched_lock(lock) ({ \ - __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_RESCHED_OFFSETS); \ - __cond_resched_lock(lock); \ +#define cond_resched_lock(lock) ({ \ + __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_RESCHED_OFFSETS, false);= \ + __cond_resched_lock(lock); \ }) =20 -#define cond_resched_rwlock_read(lock) ({ \ - __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_RESCHED_OFFSETS); \ - __cond_resched_rwlock_read(lock); \ +#define cond_resched_rwlock_read(lock) ({ \ + __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_RESCHED_OFFSETS, false);= \ + __cond_resched_rwlock_read(lock); \ }) =20 -#define cond_resched_rwlock_write(lock) ({ \ - __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_RESCHED_OFFSETS); \ - __cond_resched_rwlock_write(lock); \ +#define cond_resched_rwlock_write(lock) ({ \ + __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_RESCHED_OFFSETS, false);= \ + __cond_resched_rwlock_write(lock); \ }) =20 #ifndef CONFIG_PREEMPT_RT diff --git a/kernel/locking/spinlock_rt.c b/kernel/locking/spinlock_rt.c index 1d5e1b3c60bfa..0a89e7f10af18 100644 --- a/kernel/locking/spinlock_rt.c +++ b/kernel/locking/spinlock_rt.c @@ -33,7 +33,7 @@ (rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT) =20 #define rtlock_might_resched() \ - __might_resched(__FILE__, __LINE__, RTLOCK_RESCHED_OFFSETS) + __might_resched(__FILE__, __LINE__, RTLOCK_RESCHED_OFFSETS, true) =20 static __always_inline void rtlock_lock(struct rt_mutex_base *rtm) { diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 1fe40de6ebe3c..0135822afdd1d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9190,7 +9190,7 @@ void __might_sleep(const char *file, int line) (void *)current->task_state_change, (void *)current->task_state_change); =20 - __might_resched(file, line, 0); + __might_resched(file, line, 0, false); } EXPORT_SYMBOL(__might_sleep); =20 @@ -9215,7 +9215,8 @@ static inline bool resched_offsets_ok(unsigned int of= fsets) return nested =3D=3D offsets; } =20 -void __might_resched(const char *file, int line, unsigned int offsets) +void __might_resched(const char *file, int line, unsigned int offsets, + bool rt_sleeping_lock) { /* Ratelimiting timestamp: */ static unsigned long prev_jiffy; @@ -9226,7 +9227,7 @@ void __might_resched(const char *file, int line, unsi= gned int offsets) rcu_sleep_check(); =20 if ((resched_offsets_ok(offsets) && !irqs_disabled() && - !is_idle_task(current) && !current->non_block_count) || + !is_idle_task(current) && (rt_sleeping_lock || !current->non_block_c= ount)) || system_state =3D=3D SYSTEM_BOOTING || system_state > SYSTEM_RUNNING || oops_in_progress) return; --=20 2.55.0