Messages in this thread Patch in this message |  | | | Subject | Re: INFO: possible circular locking dependency detected | | From | Steven Rostedt <> | | Date | Fri, 15 Jul 2011 13:42:31 -0400 |
| |
On Fri, 2011-07-15 at 10:24 -0700, Paul E. McKenney wrote:
> But the rcu_read_unlock() called from within the irq handler would > take a second snapshot of ->special. It could then enter > rcu_read_unlock_special().
You agree that an interrupt preempting the rcu_read_unlock() is causing the issues correct? But it is also contained within rcu_read_unlock(). That is, we just don't want interrupts or softirqs from calling the special function when it preempted rcu_read_unlock().
How about this patch? (again totally untested and not even compiled)
-- Steve
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 7784bd2..0bdf0ea 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -46,6 +46,8 @@ #include <linux/module.h> #include <linux/hardirq.h> +DEFINE_PER_CPU(int, in_rcu_read_unlock); + #ifdef CONFIG_DEBUG_LOCK_ALLOC static struct lock_class_key rcu_lock_key; struct lockdep_map rcu_lock_map = diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 14dc7dd..a4adbb7 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -375,6 +375,8 @@ static void rcu_read_unlock_special(struct task_struct *t) } } +DECLARE_PER_CPU(int, in_rcu_read_unlock); + /* * Tree-preemptible RCU implementation for rcu_read_unlock(). * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost @@ -386,12 +388,16 @@ void __rcu_read_unlock(void) { struct task_struct *t = current; + get_cpu_var(in_rcu_read_unlock)++; barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ --t->rcu_read_lock_nesting; barrier(); /* decrement before load of ->rcu_read_unlock_special */ if (t->rcu_read_lock_nesting == 0 && + __get_cpu_var(in_rcu_read_unlock) == 1 && unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) rcu_read_unlock_special(t); + __get_cpu_var(in_rcu_read_unlock)--; + put_cpu_var(in_rcu_read_unlock); #ifdef CONFIG_PROVE_LOCKING WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0); #endif /* #ifdef CONFIG_PROVE_LOCKING */
|  |