[PATCH] s390: cputime misaccounting

finish_arch_switch needs to update the user cpu time as well, not just the
system cpu time.  Otherwise the partial user cpu time of a process that is
stored in the lowcore will be (mis-)accounted to the next process.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 27 insertions, 2 deletions

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index b0d8ca8e5eeb..7c0fe152a111 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -214,7 +214,7 @@ void account_ticks(struct pt_regs *regs)
 #endif
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
-        account_user_vtime(current);
+        account_tick_vtime(current);
 #else
         while (ticks--)
                 update_process_times(user_mode(regs));
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 22a895ecb7a4..dfe6f0856617 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -32,7 +32,7 @@ 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_user_vtime(struct task_struct *tsk)
+void account_tick_vtime(struct task_struct *tsk)
 {
         cputime_t cputime;
         __u64 timer, clock;
@@ -76,6 +76,31 @@ void account_user_vtime(struct task_struct *tsk)
  * Update process times based on virtual cpu times stored by entry.S
  * to the lowcore fields user_timer, system_timer & steal_clock.
  */
+void account_vtime(struct task_struct *tsk)
+{
+        cputime_t cputime;
+        __u64 timer;
+
+        timer = S390_lowcore.last_update_timer;
+        asm volatile ("  STPT %0"    /* Store current cpu timer value */
+                      : "=m" (S390_lowcore.last_update_timer) );
+        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
+
+        cputime = S390_lowcore.user_timer >> 12;
+        S390_lowcore.user_timer -= cputime << 12;
+        S390_lowcore.steal_clock -= cputime << 12;
+        account_user_time(tsk, cputime);
+
+        cputime =  S390_lowcore.system_timer >> 12;
+        S390_lowcore.system_timer -= cputime << 12;
+        S390_lowcore.steal_clock -= cputime << 12;
+        account_system_time(tsk, 0, cputime);
+}
+
+/*
+ * Update process times based on virtual cpu times stored by entry.S
+ * to the lowcore fields user_timer, system_timer & steal_clock.
+ */
 void account_system_vtime(struct task_struct *tsk)
 {
         cputime_t cputime;