From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965245AbeEYJFp (ORCPT ); Fri, 25 May 2018 05:05:45 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:55000 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965078AbeEYJFl (ORCPT ); Fri, 25 May 2018 05:05:41 -0400 From: Anna-Maria Gleixner To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, bigeasy@linutronix.de, paulmck@linux.vnet.ibm.com, ebiederm@xmission.com, Anna-Maria Gleixner Subject: [PATCH v2 2/2] signal: Remove no longer required irqsave/restore Date: Fri, 25 May 2018 11:05:07 +0200 Message-Id: <20180525090507.22248-3-anna-maria@linutronix.de> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180525090507.22248-1-anna-maria@linutronix.de> References: <20180525090507.22248-1-anna-maria@linutronix.de> X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit a841796f11c9 ("signal: align __lock_task_sighand() irq disabling and RCU") introduced a rcu read side critical section with interrupts disabled. The changelog suggested that a better long-term fix would be "to make rt_mutex_unlock() disable irqs when acquiring the rt_mutex structure's ->wait_lock". This long-term fix has been made in commit b4abf91047cf ("rtmutex: Make wait_lock irq safe") for a different reason. Therefore revert commit a841796f11c9 ("signal: align > __lock_task_sighand() irq disabling and RCU") as the interrupt disable dance is not longer required. The change was tested on the base of b4abf91047cf ("rtmutex: Make wait_lock irq safe") with a four hour run of rcutorture scenario TREE03 with lockdep enabled as suggested by Paul McKenney. Signed-off-by: Anna-Maria Gleixner Acked-by: Paul E. McKenney --- kernel/signal.c | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 9c33163a6165..19679ad77aa6 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1244,19 +1244,12 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, { struct sighand_struct *sighand; + rcu_read_lock(); for (;;) { - /* - * Disable interrupts early to avoid deadlocks. - * See rcu_read_unlock() comment header for details. - */ - local_irq_save(*flags); - rcu_read_lock(); sighand = rcu_dereference(tsk->sighand); - if (unlikely(sighand == NULL)) { - rcu_read_unlock(); - local_irq_restore(*flags); + if (unlikely(sighand == NULL)) break; - } + /* * This sighand can be already freed and even reused, but * we rely on SLAB_TYPESAFE_BY_RCU and sighand_ctor() which @@ -1268,15 +1261,12 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, * __exit_signal(). In the latter case the next iteration * must see ->sighand == NULL. */ - spin_lock(&sighand->siglock); - if (likely(sighand == tsk->sighand)) { - rcu_read_unlock(); + spin_lock_irqsave(&sighand->siglock, *flags); + if (likely(sighand == tsk->sighand)) break; - } - spin_unlock(&sighand->siglock); - rcu_read_unlock(); - local_irq_restore(*flags); + spin_unlock_irqrestore(&sighand->siglock, *flags); } + rcu_read_unlock(); return sighand; } -- 2.15.1