On Tue, Dec 02, 2014 at 05:24:39PM -0200, Dâniel Fraga wrote:
> On Tue, 2 Dec 2014 11:11:43 -0800
> "Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote:
>
> > OK. I need to know exactly what version of the Linux kernel you are
> > using. 3.18-rc7? (I am not too worried about exactly which version
> > you are using as long as I know which version it is.)
>
> Ok, I stopped bisecting and went back to 3.17.0 stock kernel.
> I'm testing with 3.17.0 kernel because this one is the first to show
> problems. If you want me to go to 3.18-rc7, just ask I can checkout
> through git.
>
> Ps: my signature will reflect the kernel I'm using now ;)
And I left out a step. Let's make sure that my preempt_disabled() hack
to CONFIG_TREE_PREEMPT_RCU=y has the same effect as the Kconfig hack
that allowed CONFIG_PREEMPT=y and CONFIG_TREE_PREEMPT_RCU=n. Could you
please try out the following patch configured with CONFIG_PREEMPT=y
and CONFIG_TREE_PREEMPT_RCU=y?
Thanx, Paul
------------------------------------------------------------------------
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index e0d31a345ee6..fff605a9e87f 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -71,7 +71,11 @@ module_param(rcu_expedited, int, 0);
*/
void __rcu_read_lock(void)
{
- current->rcu_read_lock_nesting++;
+ struct task_struct *t = current;
+
+ if (!t->rcu_read_lock_nesting)
+ preempt_disable();
+ t->rcu_read_lock_nesting++;
barrier(); /* critical section after entry code. */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
@@ -92,6 +96,7 @@ void __rcu_read_unlock(void)
} else {
barrier(); /* critical section before exit code. */
t->rcu_read_lock_nesting = INT_MIN;
+ preempt_enable();
barrier(); /* assign before ->rcu_read_unlock_special load */
if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
--
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