s390/vtime: correct system time accounting
There is a slight misaccounting of system time in vtime_account_user. This function is called once per HZ tick in interrupt context. The irq_enter function already accounted the system time up to the point of the irq_enter call. The system time from irq_enter until vtime_account_user/do_account_vtime is reached is irq time but it is accounted to the previous context. Just drop the hardirq offset from arch/s390/kernel/vtime.c. Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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@ -94,7 +94,7 @@ static void update_mt_scaling(void)
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* Update process times based on virtual cpu times stored by entry.S
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* Update process times based on virtual cpu times stored by entry.S
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* to the lowcore fields user_timer, system_timer & steal_clock.
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* to the lowcore fields user_timer, system_timer & steal_clock.
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*/
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*/
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static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
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static int do_account_vtime(struct task_struct *tsk)
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{
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{
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u64 timer, clock, user, system, steal;
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u64 timer, clock, user, system, steal;
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u64 user_scaled, system_scaled;
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u64 user_scaled, system_scaled;
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@ -138,7 +138,7 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
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}
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}
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account_user_time(tsk, user);
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account_user_time(tsk, user);
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tsk->utimescaled += user_scaled;
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tsk->utimescaled += user_scaled;
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account_system_time(tsk, hardirq_offset, system);
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account_system_time(tsk, 0, system);
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tsk->stimescaled += system_scaled;
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tsk->stimescaled += system_scaled;
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steal = S390_lowcore.steal_timer;
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steal = S390_lowcore.steal_timer;
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@ -152,7 +152,7 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
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void vtime_task_switch(struct task_struct *prev)
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void vtime_task_switch(struct task_struct *prev)
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{
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{
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do_account_vtime(prev, 0);
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do_account_vtime(prev);
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prev->thread.user_timer = S390_lowcore.user_timer;
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prev->thread.user_timer = S390_lowcore.user_timer;
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prev->thread.system_timer = S390_lowcore.system_timer;
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prev->thread.system_timer = S390_lowcore.system_timer;
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S390_lowcore.user_timer = current->thread.user_timer;
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S390_lowcore.user_timer = current->thread.user_timer;
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@ -166,7 +166,7 @@ void vtime_task_switch(struct task_struct *prev)
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*/
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*/
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void vtime_account_user(struct task_struct *tsk)
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void vtime_account_user(struct task_struct *tsk)
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{
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{
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if (do_account_vtime(tsk, HARDIRQ_OFFSET))
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if (do_account_vtime(tsk))
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virt_timer_expire();
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virt_timer_expire();
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}
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}
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