3.2.55-rt79-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Tiejun Chen <tiejun.chen@xxxxxxxxxxxxx>
Any callers to the function rcu_preempt_qs() must disable irqs in
order to protect the assignment to ->rcu_read_unlock_special. In
RT case, rcu_bh_qs() as the wrapper of rcu_preempt_qs() is called
in some scenarios where irq is enabled, like this path,
do_single_softirq()
|
+ local_irq_enable();
+ handle_softirq()
| |
| + rcu_bh_qs()
| |
| + rcu_preempt_qs()
|
+ local_irq_disable()
So here we'd better disable irq directly inside of rcu_bh_qs() to
fix this, otherwise the kernel may be freezable sometimes as
observed. And especially this way is also kind and safe for the
potential rcu_bh_qs() usage elsewhere in the future.
Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxxxxxx>
Signed-off-by: Bin Jiang <bin.jiang@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/rcutree.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 82c2224..6c2ec2d 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -175,7 +175,12 @@ static void rcu_preempt_qs(int cpu);
void rcu_bh_qs(int cpu)
{
+ unsigned long flags;
+
+ /* Callers to this function, rcu_preempt_qs(), must disable irqs. */
+ local_irq_save(flags);
rcu_preempt_qs(cpu);
+ local_irq_restore(flags);
}
#else
void rcu_bh_qs(int cpu)
--
1.8.5.3
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