All of lore.kernel.org
 help / color / mirror / Atom feed
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, "Eric W. Biederman" <ebiederm@xmission.com>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH] kernel/signal: Remove no longer required irqsave/restore
Date: Fri,  4 May 2018 16:40:14 +0200	[thread overview]
Message-ID: <20180504144014.5378-1-bigeasy@linutronix.de> (raw)

From: Anna-Maria Gleixner <anna-maria@linutronix.de>

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 4abf91047cf ("rtmutex: Make >
wait_lock irq safe") for different reason.

Therefore revert commit a841796f11c9 ("signal: align >
__lock_task_sighand() irq disabling and RCU") as the interrupt disable
dance is not longer required.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/signal.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index c6e4c83dc090..16b87c54d027 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;
 }
-- 
2.17.0

             reply	other threads:[~2018-05-04 14:40 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-04 14:40 Sebastian Andrzej Siewior [this message]
2018-05-04 16:59 ` Eric W. Biederman
2018-05-04 17:04   ` Sebastian Andrzej Siewior
2018-05-04 17:17     ` Eric W. Biederman
2018-05-04 17:52       ` Paul E. McKenney
2018-05-04 19:03         ` Eric W. Biederman
2018-05-04 19:45           ` Paul E. McKenney
2018-05-04 20:08             ` Eric W. Biederman
2018-05-04 20:37               ` Paul E. McKenney
2018-05-05  4:38                 ` Eric W. Biederman
2018-05-05  5:25                   ` Paul E. McKenney
2018-05-05  5:56                     ` Thomas Gleixner
2018-05-08 13:42                       ` Anna-Maria Gleixner
2018-05-08 14:53                         ` Paul E. McKenney
2018-05-08 15:49                           ` Anna-Maria Gleixner
2018-05-08 16:53                             ` Paul E. McKenney
2018-06-07 20:21 ` [tip:core/urgent] signal: " tip-bot for Anna-Maria Gleixner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180504144014.5378-1-bigeasy@linutronix.de \
    --to=bigeasy@linutronix.de \
    --cc=anna-maria@linutronix.de \
    --cc=ebiederm@xmission.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=tglx@linutronix.de \
    --subject='Re: [PATCH] kernel/signal: Remove no longer required irqsave/restore' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.