cputime: Consolidate vtime handling on context switch

The archs that implement virtual cputime accounting all
flush the cputime of a task when it gets descheduled
and sometimes set up some ground initialization for the
next task to account its cputime.

These archs all put their own hooks in their context
switch callbacks and handle the off-case themselves.

Consolidate this by creating a new account_switch_vtime()
callback called in generic code right after a context switch
and that these archs must implement to flush the prev task
cputime and initialize the next task cputime related state.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 2fbd9053c2df..bbe5d15d6597 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -130,4 +130,10 @@ extern void account_process_tick(struct task_struct *, int user);
 extern void account_steal_ticks(unsigned long ticks);
 extern void account_idle_ticks(unsigned long ticks);
 
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+extern void account_switch_vtime(struct task_struct *prev);
+#else
+static inline void account_switch_vtime(struct task_struct *prev) { }
+#endif
+
 #endif /* _LINUX_KERNEL_STAT_H */