sched: restore deterministic CPU accounting on powerpc

Since powerpc started using CONFIG_GENERIC_CLOCKEVENTS, the
deterministic CPU accounting (CONFIG_VIRT_CPU_ACCOUNTING) has been
broken on powerpc, because we end up counting user time twice: once in
timer_interrupt() and once in update_process_times().

This fixes the problem by pulling the code in update_process_times
that updates utime and stime into a separate function called
account_process_tick.  If CONFIG_VIRT_CPU_ACCOUNTING is not defined,
there is a version of account_process_tick in kernel/timer.c that
simply accounts a whole tick to either utime or stime as before.  If
CONFIG_VIRT_CPU_ACCOUNTING is defined, then arch code gets to
implement account_process_tick.

This also lets us simplify the s390 code a bit; it means that the s390
timer interrupt can now call update_process_times even when
CONFIG_VIRT_CPU_ACCOUNTING is turned on, and can just implement a
suitable account_process_tick().

account_process_tick() now takes the task_struct * as an argument.
Tested both with and without CONFIG_VIRT_CPU_ACCOUNTING.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 1 insertions, 11 deletions

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index a963fe81359e..22b800ce2126 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -145,12 +145,8 @@ void account_ticks(u64 time)
         do_timer(ticks);
 #endif
 
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING
-        account_tick_vtime(current);
-#else
         while (ticks--)
                 update_process_times(user_mode(get_irq_regs()));
-#endif
 
         s390_do_profile();
 }
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 84ff78de6bac..c5f05b3fb2c3 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -32,7 +32,7 @@ static DEFINE_PER_CPU(struct vtimer_queue, virt_cpu_timer);
  * Update process times based on virtual cpu times stored by entry.S
  * to the lowcore fields user_timer, system_timer & steal_clock.
  */
-void account_tick_vtime(struct task_struct *tsk)
+void account_process_tick(struct task_struct *tsk, int user_tick)
 {
         cputime_t cputime;
         __u64 timer, clock;
@@ -64,12 +64,6 @@ void account_tick_vtime(struct task_struct *tsk)
                 S390_lowcore.steal_clock -= cputime << 12;
                 account_steal_time(tsk, cputime);
         }
-
-        run_local_timers();
-        if (rcu_pending(smp_processor_id()))
-                rcu_check_callbacks(smp_processor_id(), rcu_user_flag);
-        scheduler_tick();
-        run_posix_cpu_timers(tsk);
 }
 
 /*