From nobody Sun Feb 8 18:11:07 2026 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 90E01188CC8; Thu, 8 Aug 2024 10:22:44 +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=1723112566; cv=none; b=Qug/3QtZjMv1nor8C5UMBNxBaVxONNlM6LLz+ZaeygVV75IyYzkDkwIFnQFf6xKMQ29NFA1I+UYD4qw73r+mogc3PRtvXEj1x0Fc2POdsdd/JRfciAw/5NHqJ6CUXCmkIB3ntqQu7TebD5OEBN/LsiHXXy6cCvSPw/gm27xYfJM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723112566; c=relaxed/simple; bh=eKfXnQfAW+gFwOPdWuItPVF+vMtgQJSKy6siEECFM3Y=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=ddS6owy/y1qVLEhCxacPBw7DuRzm1x7YCWaWuTZq9tNDxW17PqrnG6fpHZoTsTq3BjSpRiQqUnXr8iPmeEi5u0W61lIGf0c39+5LNfzGVaAgusupT3UF5W/4ozwahX2QZkpSo9FzZP6DrRCoS0pv2thB/2bmi7S3tTMU2NcT8Zw= 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=mAZqoT7/; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Bu1tCBPE; 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="mAZqoT7/"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Bu1tCBPE" Date: Thu, 08 Aug 2024 10:22:42 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1723112562; h=from:from:sender:sender:reply-to: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=Fy4n7vO6FF7aqXUHJIcIR/Bu/Y4ez3yxcEk8WpUja/Q=; b=mAZqoT7/YbIyRChhot3wv72064oSu8JPzFbAWe1B5xYEhOV+2qOmKZV/8ds88bzWPzyeNC vJhnPKkTCA/DVqsXwrLm3HOUjO6knrEp6ImNuew38h8PhwSo+bwilqKyRBqbgbVKjil+ch DtNRT7Voqx2E9AveJ1zKGjM6omRqVxvk4/O+eZYNVNRTZPQ+tqooa3SyWGQENZi5Ow3tK1 pmVSF+xwpLBMxwIevVXRXNamRc4GSaQ62VWD7LXz8tzgsGPWoKO8veC5yMJm6QkcDflVaJ QJqshM1BaABsKcuwoG3djfgynRlmjZfLtaAQL4GAxAu8X/zFVLuOpbcQWIx73A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1723112562; h=from:from:sender:sender:reply-to: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=Fy4n7vO6FF7aqXUHJIcIR/Bu/Y4ez3yxcEk8WpUja/Q=; b=Bu1tCBPEB1BjF2u0Do8u0rsW6iZkIfZAlJ12nuAFujvv7L5qye1NPwy1ztMuTVudU8CriI Axe1+O7CleIWkEBQ== From: "tip-bot2 for Zhiguo Niu" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/core] lockdep: fix deadlock issue between lockdep and rcu Cc: stable@vger.kernel.org, Boqun Feng , Waiman Long , Carlos Llamas , Bart Van Assche , Zhiguo Niu , Xuewen Yan , "Paul E. McKenney" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20240620225436.3127927-1-cmllamas@google.com> References: <20240620225436.3127927-1-cmllamas@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <172311256240.2215.14227366468981064176.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the locking/core branch of tip: Commit-ID: a6f88ac32c6e63e69c595bfae220d8641704c9b7 Gitweb: https://git.kernel.org/tip/a6f88ac32c6e63e69c595bfae220d8641= 704c9b7 Author: Zhiguo Niu AuthorDate: Thu, 20 Jun 2024 22:54:34=20 Committer: Boqun Feng CommitterDate: Tue, 06 Aug 2024 10:46:42 -07:00 lockdep: fix deadlock issue between lockdep and rcu There is a deadlock scenario between lockdep and rcu when rcu nocb feature is enabled, just as following call stack: rcuop/x -000|queued_spin_lock_slowpath(lock =3D 0xFFFFFF817F2A8A80, val =3D ?) -001|queued_spin_lock(inline) // try to hold nocb_gp_lock -001|do_raw_spin_lock(lock =3D 0xFFFFFF817F2A8A80) -002|__raw_spin_lock_irqsave(inline) -002|_raw_spin_lock_irqsave(lock =3D 0xFFFFFF817F2A8A80) -003|wake_nocb_gp_defer(inline) -003|__call_rcu_nocb_wake(rdp =3D 0xFFFFFF817F30B680) -004|__call_rcu_common(inline) -004|call_rcu(head =3D 0xFFFFFFC082EECC28, func =3D ?) -005|call_rcu_zapped(inline) -005|free_zapped_rcu(ch =3D ?)// hold graph lock -006|rcu_do_batch(rdp =3D 0xFFFFFF817F245680) -007|nocb_cb_wait(inline) -007|rcu_nocb_cb_kthread(arg =3D 0xFFFFFF817F245680) -008|kthread(_create =3D 0xFFFFFF80803122C0) -009|ret_from_fork(asm) rcuop/y -000|queued_spin_lock_slowpath(lock =3D 0xFFFFFFC08291BBC8, val =3D 0) -001|queued_spin_lock() -001|lockdep_lock() -001|graph_lock() // try to hold graph lock -002|lookup_chain_cache_add() -002|validate_chain() -003|lock_acquire -004|_raw_spin_lock_irqsave(lock =3D 0xFFFFFF817F211D80) -005|lock_timer_base(inline) -006|mod_timer(inline) -006|wake_nocb_gp_defer(inline)// hold nocb_gp_lock -006|__call_rcu_nocb_wake(rdp =3D 0xFFFFFF817F2A8680) -007|__call_rcu_common(inline) -007|call_rcu(head =3D 0xFFFFFFC0822E0B58, func =3D ?) -008|call_rcu_hurry(inline) -008|rcu_sync_call(inline) -008|rcu_sync_func(rhp =3D 0xFFFFFFC0822E0B58) -009|rcu_do_batch(rdp =3D 0xFFFFFF817F266680) -010|nocb_cb_wait(inline) -010|rcu_nocb_cb_kthread(arg =3D 0xFFFFFF817F266680) -011|kthread(_create =3D 0xFFFFFF8080363740) -012|ret_from_fork(asm) rcuop/x and rcuop/y are rcu nocb threads with the same nocb gp thread. This patch release the graph lock before lockdep call_rcu. Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer= in use") Cc: stable@vger.kernel.org Cc: Boqun Feng Cc: Waiman Long Cc: Carlos Llamas Cc: Bart Van Assche Signed-off-by: Zhiguo Niu Signed-off-by: Xuewen Yan Reviewed-by: Waiman Long Reviewed-by: Carlos Llamas Reviewed-by: Bart Van Assche Signed-off-by: Carlos Llamas Acked-by: Paul E. McKenney Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20240620225436.3127927-1-cmllamas@google.com --- kernel/locking/lockdep.c | 48 ++++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 16 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 266f57f..b172ead 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -6186,25 +6186,27 @@ static struct pending_free *get_pending_free(void) static void free_zapped_rcu(struct rcu_head *cb); =20 /* - * Schedule an RCU callback if no RCU callback is pending. Must be called = with - * the graph lock held. - */ -static void call_rcu_zapped(struct pending_free *pf) +* See if we need to queue an RCU callback, must called with +* the lockdep lock held, returns false if either we don't have +* any pending free or the callback is already scheduled. +* Otherwise, a call_rcu() must follow this function call. +*/ +static bool prepare_call_rcu_zapped(struct pending_free *pf) { WARN_ON_ONCE(inside_selftest()); =20 if (list_empty(&pf->zapped)) - return; + return false; =20 if (delayed_free.scheduled) - return; + return false; =20 delayed_free.scheduled =3D true; =20 WARN_ON_ONCE(delayed_free.pf + delayed_free.index !=3D pf); delayed_free.index ^=3D 1; =20 - call_rcu(&delayed_free.rcu_head, free_zapped_rcu); + return true; } =20 /* The caller must hold the graph lock. May be called from RCU context. */ @@ -6230,6 +6232,7 @@ static void free_zapped_rcu(struct rcu_head *ch) { struct pending_free *pf; unsigned long flags; + bool need_callback; =20 if (WARN_ON_ONCE(ch !=3D &delayed_free.rcu_head)) return; @@ -6241,14 +6244,18 @@ static void free_zapped_rcu(struct rcu_head *ch) pf =3D delayed_free.pf + (delayed_free.index ^ 1); __free_zapped_classes(pf); delayed_free.scheduled =3D false; + need_callback =3D + prepare_call_rcu_zapped(delayed_free.pf + delayed_free.index); + lockdep_unlock(); + raw_local_irq_restore(flags); =20 /* - * If there's anything on the open list, close and start a new callback. - */ - call_rcu_zapped(delayed_free.pf + delayed_free.index); + * If there's pending free and its callback has not been scheduled, + * queue an RCU callback. + */ + if (need_callback) + call_rcu(&delayed_free.rcu_head, free_zapped_rcu); =20 - lockdep_unlock(); - raw_local_irq_restore(flags); } =20 /* @@ -6288,6 +6295,7 @@ static void lockdep_free_key_range_reg(void *start, u= nsigned long size) { struct pending_free *pf; unsigned long flags; + bool need_callback; =20 init_data_structures_once(); =20 @@ -6295,10 +6303,11 @@ static void lockdep_free_key_range_reg(void *start,= unsigned long size) lockdep_lock(); pf =3D get_pending_free(); __lockdep_free_key_range(pf, start, size); - call_rcu_zapped(pf); + need_callback =3D prepare_call_rcu_zapped(pf); lockdep_unlock(); raw_local_irq_restore(flags); - + if (need_callback) + call_rcu(&delayed_free.rcu_head, free_zapped_rcu); /* * Wait for any possible iterators from look_up_lock_class() to pass * before continuing to free the memory they refer to. @@ -6392,6 +6401,7 @@ static void lockdep_reset_lock_reg(struct lockdep_map= *lock) struct pending_free *pf; unsigned long flags; int locked; + bool need_callback =3D false; =20 raw_local_irq_save(flags); locked =3D graph_lock(); @@ -6400,11 +6410,13 @@ static void lockdep_reset_lock_reg(struct lockdep_m= ap *lock) =20 pf =3D get_pending_free(); __lockdep_reset_lock(pf, lock); - call_rcu_zapped(pf); + need_callback =3D prepare_call_rcu_zapped(pf); =20 graph_unlock(); out_irq: raw_local_irq_restore(flags); + if (need_callback) + call_rcu(&delayed_free.rcu_head, free_zapped_rcu); } =20 /* @@ -6448,6 +6460,7 @@ void lockdep_unregister_key(struct lock_class_key *ke= y) struct pending_free *pf; unsigned long flags; bool found =3D false; + bool need_callback =3D false; =20 might_sleep(); =20 @@ -6468,11 +6481,14 @@ void lockdep_unregister_key(struct lock_class_key *= key) if (found) { pf =3D get_pending_free(); __lockdep_free_key_range(pf, key, 1); - call_rcu_zapped(pf); + need_callback =3D prepare_call_rcu_zapped(pf); } lockdep_unlock(); raw_local_irq_restore(flags); =20 + if (need_callback) + call_rcu(&delayed_free.rcu_head, free_zapped_rcu); + /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ synchronize_rcu(); }