rcu: Make rcu_blocking_is_gp() stop early-boot might_sleep()

Currently, rcu_blocking_is_gp() invokes might_sleep() even during early
boot when interrupts are disabled and before the scheduler is scheduling.
This is at best an accident waiting to happen.  Therefore, this commit
moves that might_sleep() under an rcu_scheduler_active check in order
to ensure that might_sleep() is not invoked unless sleeping might actually
happen.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0147e69..15f9765 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3333,9 +3333,10 @@ void __init kfree_rcu_scheduler_running(void)
  */
 static int rcu_blocking_is_gp(void)
 {
-       if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
+       if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE) {
+               might_sleep();
                return false;
-       might_sleep();  /* Check for RCU read-side critical section. */
+       }
        return true;
 }