Messages in this thread Patch in this message | | | From | Sebastian Andrzej Siewior <> | Subject | [PATCH] kernel/signal: Remove no longer required irqsave/restore | Date | Fri, 4 May 2018 16:40:14 +0200 |
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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
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