s390/vtime: Get rid of redundant WARN_ON

in the cpu time accounting function vtime_account_irq_enter
(vtime_account_system) we use a WARN_ON_ONCE(!irqs_disabled()).
This is redundant as the function virt_timer_forward is always
called and has a BUG_ON(!irqs_disabled()).

This saves several nanoseconds in my specific testcase (KVM entry/exit)
and probably all other callers like (soft)irq entry/exit.

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

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 7f0089d..e34122e 100644 (file)
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -128,8 +128,6 @@ void vtime_account_irq_enter(struct task_struct *tsk)
        struct thread_info *ti = task_thread_info(tsk);
        u64 timer, system;
 
-       WARN_ON_ONCE(!irqs_disabled());
-
        timer = S390_lowcore.last_update_timer;
        S390_lowcore.last_update_timer = get_vtimer();
        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;