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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CDC47C43215 for ; Tue, 19 Nov 2019 14:47:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9A3AC222EF for ; Tue, 19 Nov 2019 14:47:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574174837; bh=gDox6nHTvPDLYkDr0P7VZdMIOKHTU1y6ZfkQibEdeqY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=XB56RtQZVCATTt4l1ldvF/2NFUmGH78JkPxdMxlXaT4kZprqf1818SyB0ca0CY8va Eac9quSF0QAnsFVsv+qenamjyy9B/W5hrOXbFx4IWpEPTNRBuY8cY7k+xp3HulK4Gn egPk+O0pCvlMXV4qQ8VKVtO4UBmDNKADFzK8xjv8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728330AbfKSOrM (ORCPT ); Tue, 19 Nov 2019 09:47:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:60400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727316AbfKSOrM (ORCPT ); Tue, 19 Nov 2019 09:47:12 -0500 Received: from paulmck-ThinkPad-P72.home (199-192-87-166.static.wiline.com [199.192.87.166]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 256DB222D1; Tue, 19 Nov 2019 14:47:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574174831; bh=gDox6nHTvPDLYkDr0P7VZdMIOKHTU1y6ZfkQibEdeqY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=nkyzsi3CC68t2roIyojFz6hHMc8BpahtgdhYcQzsb7zj9RVkfOYo90feQ8Hzc7LEk CUiBN+PMozu+9IVJdT5Ub5V2Eiw6PTT5TqinkBtvISHH/Ehe7Zhlz40fzRkFpuRAXF d8ZpH1y8RZ0HZW0D3ZxYnkcRDMpHulmJNlW3dwig= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id C8E0C3520B06; Tue, 19 Nov 2019 06:47:10 -0800 (PST) Date: Tue, 19 Nov 2019 06:47:10 -0800 From: "Paul E. McKenney" To: Sebastian Andrzej Siewior Cc: LKML , linux-rt-users , Steven Rostedt , Thomas Gleixner Subject: Re: [PATCH RT] locking: Make spinlock_t and rwlock_t a RCU section on RT Message-ID: <20191119144710.GW2889@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20191119084640.wgsxghvc62mxlqc3@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191119084640.wgsxghvc62mxlqc3@linutronix.de> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Tue, Nov 19, 2019 at 09:46:40AM +0100, Sebastian Andrzej Siewior wrote: > On !RT a locked spinlock_t and rwlock_t disables preemption which > implies a RCU read section. There is code that relies on that behaviour. > > Add an explicit RCU read section on RT while a sleeping lock (a lock > which would disables preemption on !RT) acquired. > > Signed-off-by: Sebastian Andrzej Siewior Acked-by: Paul E. McKenney > --- > kernel/locking/rtmutex.c | 6 ++++++ > kernel/locking/rwlock-rt.c | 6 ++++++ > 2 files changed, 12 insertions(+) > > diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c > index cf09f8e7ed0f4..602eb7821a1b1 100644 > --- a/kernel/locking/rtmutex.c > +++ b/kernel/locking/rtmutex.c > @@ -1141,6 +1141,7 @@ void __sched rt_spin_lock_slowunlock(struct rt_mutex *lock) > void __lockfunc rt_spin_lock(spinlock_t *lock) > { > sleeping_lock_inc(); > + rcu_read_lock(); > migrate_disable(); > spin_acquire(&lock->dep_map, 0, 0, _RET_IP_); > rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock); > @@ -1156,6 +1157,7 @@ void __lockfunc __rt_spin_lock(struct rt_mutex *lock) > void __lockfunc rt_spin_lock_nested(spinlock_t *lock, int subclass) > { > sleeping_lock_inc(); > + rcu_read_lock(); > migrate_disable(); > spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_); > rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock); > @@ -1169,6 +1171,7 @@ void __lockfunc rt_spin_unlock(spinlock_t *lock) > spin_release(&lock->dep_map, 1, _RET_IP_); > rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock); > migrate_enable(); > + rcu_read_unlock(); > sleeping_lock_dec(); > } > EXPORT_SYMBOL(rt_spin_unlock); > @@ -1200,6 +1203,7 @@ int __lockfunc rt_spin_trylock(spinlock_t *lock) > ret = __rt_mutex_trylock(&lock->lock); > if (ret) { > spin_acquire(&lock->dep_map, 0, 1, _RET_IP_); > + rcu_read_lock(); > } else { > migrate_enable(); > sleeping_lock_dec(); > @@ -1216,6 +1220,7 @@ int __lockfunc rt_spin_trylock_bh(spinlock_t *lock) > ret = __rt_mutex_trylock(&lock->lock); > if (ret) { > sleeping_lock_inc(); > + rcu_read_lock(); > migrate_disable(); > spin_acquire(&lock->dep_map, 0, 1, _RET_IP_); > } else > @@ -1232,6 +1237,7 @@ int __lockfunc rt_spin_trylock_irqsave(spinlock_t *lock, unsigned long *flags) > ret = __rt_mutex_trylock(&lock->lock); > if (ret) { > sleeping_lock_inc(); > + rcu_read_lock(); > migrate_disable(); > spin_acquire(&lock->dep_map, 0, 1, _RET_IP_); > } > diff --git a/kernel/locking/rwlock-rt.c b/kernel/locking/rwlock-rt.c > index c3b91205161cc..0ae8c62ea8320 100644 > --- a/kernel/locking/rwlock-rt.c > +++ b/kernel/locking/rwlock-rt.c > @@ -310,6 +310,7 @@ int __lockfunc rt_read_trylock(rwlock_t *rwlock) > ret = do_read_rt_trylock(rwlock); > if (ret) { > rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_); > + rcu_read_lock(); > } else { > migrate_enable(); > sleeping_lock_dec(); > @@ -327,6 +328,7 @@ int __lockfunc rt_write_trylock(rwlock_t *rwlock) > ret = do_write_rt_trylock(rwlock); > if (ret) { > rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_); > + rcu_read_lock(); > } else { > migrate_enable(); > sleeping_lock_dec(); > @@ -338,6 +340,7 @@ EXPORT_SYMBOL(rt_write_trylock); > void __lockfunc rt_read_lock(rwlock_t *rwlock) > { > sleeping_lock_inc(); > + rcu_read_lock(); > migrate_disable(); > rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_); > do_read_rt_lock(rwlock); > @@ -347,6 +350,7 @@ EXPORT_SYMBOL(rt_read_lock); > void __lockfunc rt_write_lock(rwlock_t *rwlock) > { > sleeping_lock_inc(); > + rcu_read_lock(); > migrate_disable(); > rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_); > do_write_rt_lock(rwlock); > @@ -358,6 +362,7 @@ void __lockfunc rt_read_unlock(rwlock_t *rwlock) > rwlock_release(&rwlock->dep_map, 1, _RET_IP_); > do_read_rt_unlock(rwlock); > migrate_enable(); > + rcu_read_unlock(); > sleeping_lock_dec(); > } > EXPORT_SYMBOL(rt_read_unlock); > @@ -367,6 +372,7 @@ void __lockfunc rt_write_unlock(rwlock_t *rwlock) > rwlock_release(&rwlock->dep_map, 1, _RET_IP_); > do_write_rt_unlock(rwlock); > migrate_enable(); > + rcu_read_unlock(); > sleeping_lock_dec(); > } > EXPORT_SYMBOL(rt_write_unlock); > -- > 2.24.0 >