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Groups > linux.kernel > #1552149

[PATCH 01/10] powerpc32: Fix stale scaled stime on context switch

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On context switch with powerpc32, the cputime is accumulated in the
thread_info struct. So the switching-in task must move forward its
start time snapshot to the current time in order to later compute the
delta spent in system mode.

This is what we do for the normal cputime by initializing the starttime
field to the value of the previous task's starttime which got freshly
updated.

But we are missing the update of the scaled cputime start time. As a
result we may be accounting too much scaled cputime later.

Fix this by initializing the scaled cputime the same way we do for
normal cputime.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 arch/powerpc/kernel/time.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index bc2e08d..ce21650 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -407,6 +407,7 @@ void arch_vtime_task_switch(struct task_struct *prev)
 	struct cpu_accounting_data *acct = get_accounting(current);
 
 	acct->starttime = get_accounting(prev)->starttime;
+	acct->startspurr = get_accounting(prev)->startspurr;
 	acct->system_time = 0;
 	acct->user_time = 0;
 }
-- 
2.7.4

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[PATCH 00/10] vtime: Delay cputime accounting to tick / context switch Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-05 18:20 +0100
  [PATCH 09/10] s390/cputime: delayed accounting of system time Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-05 18:20 +0100
    [tip:sched/core] sched/cputime, s390: Implement delayed accounting  of system time tip-bot for Martin Schwidefsky <tipbot@zytor.com> - 2017-01-14 11:10 +0100
  [PATCH 08/10] ia64: Accumulate cputime and account only on tick/task switch Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-05 18:20 +0100
    [tip:sched/core] sched/cputime, ia64: Accumulate cputime and  account only on tick/task switch tip-bot for Frederic Weisbecker <tipbot@zytor.com> - 2017-01-14 11:10 +0100
  [PATCH 07/10] powerpc/vtime: Accumulate cputime and account only on tick/task switch Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-05 18:20 +0100
    [tip:sched/core] sched/cputime, powerpc/vtime: Accumulate cputime  and account only on tick/task switch tip-bot for Frederic Weisbecker <tipbot@zytor.com> - 2017-01-14 11:10 +0100
  [PATCH 01/10] powerpc32: Fix stale scaled stime on context switch Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-05 18:20 +0100
    [tip:sched/core] sched/cputime, powerpc32: Fix stale scaled stime  on context switch tip-bot for Frederic Weisbecker <tipbot@zytor.com> - 2017-01-14 11:10 +0100
  [PATCH 06/10] powerpc: Migrate stolen_time field to accounting structure Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-05 18:20 +0100
    [tip:sched/core] sched/cputime, powerpc: Migrate stolen_time field  to the accounting structure tip-bot for Frederic Weisbecker <tipbot@zytor.com> - 2017-01-14 11:10 +0100
  Re: [PATCH 00/10] vtime: Delay cputime accounting to tick / context  switch Martin Schwidefsky <schwidefsky@de.ibm.com> - 2017-01-09 09:20 +0100
  Re: [PATCH 00/10] vtime: Delay cputime accounting to tick / context  switch Thomas Gleixner <tglx@linutronix.de> - 2017-01-10 12:50 +0100
    Re: [PATCH 00/10] vtime: Delay cputime accounting to tick / context  switch Frederic Weisbecker <fweisbec@gmail.com> - 2017-01-10 16:30 +0100

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