[S390] idle: avoid RCU usage in extended quiescent state

Avoid calling wake_up() from our NMI "bottom halve" from RCU extended
quiescent state in idle. wake_up() has RCU read-side critical sections
but this will be completely ignored by RCU if the cpu is in extended
quiescent state.
Which means that whatever object is being accessed from within the
read-side critical section can be freed concurrently from a different
cpu.
So make sure we leave extended quiescent state before calling wake_up().

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 3201ae447990c50052d7536d079e39286a77120d..4261aa799774f5972940f22ebd1b7c7ea29220f8 100644 (file)
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -76,7 +76,6 @@ static void default_idle(void)
        if (test_thread_flag(TIF_MCCK_PENDING)) {
                local_mcck_enable();
                local_irq_enable();
-               s390_handle_mcck();
                return;
        }
        trace_hardirqs_on();
@@ -93,10 +92,12 @@ void cpu_idle(void)
        for (;;) {
                tick_nohz_idle_enter();
                rcu_idle_enter();
-               while (!need_resched())
+               while (!need_resched() && !test_thread_flag(TIF_MCCK_PENDING))
                        default_idle();
                rcu_idle_exit();
                tick_nohz_idle_exit();
+               if (test_thread_flag(TIF_MCCK_PENDING))
+                       s390_handle_mcck();
                preempt_enable_no_resched();
                schedule();
                preempt_disable();