Commit 032014bc authored Dec 12, 2014 by Christian Borntraeger Committed by Martin Schwidefsky Dec 18, 2014

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>

parent 099eae11

arch/s390/kernel/vtime.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -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;

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