Messages in this thread | | | Date | Mon, 5 May 2014 18:47:20 +0200 | From | Oleg Nesterov <> | Subject | Re: lock_task_sighand() && rcu_boost() |
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On 05/05, Paul E. McKenney wrote: > > Does the patch below cover it?
Yes, thanks.
Acked-by: Oleg Nesterov <oleg@redhat.com>
> signal: Explain local_irq_save() call > > The explicit local_irq_save() in __lock_task_sighand() is needed to avoid > a potential deadlock condition, as noted in a841796f11c90d53 (signal: > align __lock_task_sighand() irq disabling and RCU). However, someone > reading the code might be forgiven for concluding that this separate > local_irq_save() was completely unnecessary. This commit therefore adds > a comment referencing the shiny new block comment on rcu_read_unlock(). > > Reported-by: Oleg Nesterov <oleg@redhat.com> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > diff --git a/kernel/signal.c b/kernel/signal.c > index 6ea13c09ae56..513e8c252aa4 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1288,6 +1288,10 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, > struct sighand_struct *sighand; > > 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); >
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