Commit e282ccd3 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

s390/vtime: Use __this_cpu_read() / get rid of READ_ONCE() 



do_account_vtime() runs always with interrupts disabled, therefore use
__this_cpu_read() instead of this_cpu_read() to get rid of a pointless
preempt_disable() / preempt_enable() pair.

Also there are no concurrent writers to the cpu time accounting fields
in lowcore. Therefore get rid of READ_ONCE() usages.

Reviewed-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent d8b5cf9c

arch/s390/kernel/vtime.c

+7 −14
Original line number Diff line number Diff line
@@ -137,23 +137,16 @@ static int do_account_vtime(struct task_struct *tsk) 
		lc->system_timer += timer;



	/* Update MT utilization calculation */

	if (smp_cpu_mtid &&

	    time_after64(jiffies_64, this_cpu_read(mt_scaling_jiffies)))

	if (smp_cpu_mtid && time_after64(jiffies_64, __this_cpu_read(mt_scaling_jiffies)))

		update_mt_scaling();



	/* Calculate cputime delta */

	user = update_tsk_timer(&tsk->thread.user_timer,

				READ_ONCE(lc->user_timer));

	guest = update_tsk_timer(&tsk->thread.guest_timer,

				 READ_ONCE(lc->guest_timer));

	system = update_tsk_timer(&tsk->thread.system_timer,

				  READ_ONCE(lc->system_timer));

	hardirq = update_tsk_timer(&tsk->thread.hardirq_timer,

				   READ_ONCE(lc->hardirq_timer));

	softirq = update_tsk_timer(&tsk->thread.softirq_timer,

				   READ_ONCE(lc->softirq_timer));

	lc->steal_timer +=

		clock - user - guest - system - hardirq - softirq;

	user = update_tsk_timer(&tsk->thread.user_timer, lc->user_timer);

	guest = update_tsk_timer(&tsk->thread.guest_timer, lc->guest_timer);

	system = update_tsk_timer(&tsk->thread.system_timer, lc->system_timer);

	hardirq = update_tsk_timer(&tsk->thread.hardirq_timer, lc->hardirq_timer);

	softirq = update_tsk_timer(&tsk->thread.softirq_timer, lc->softirq_timer);

	lc->steal_timer += clock - user - guest - system - hardirq - softirq;



	/* Push account value */

	if (user) {