sched: Refactor account_system_time separating id-update

Refactor account_system_time, to separate out the logic of
identifying the update needed and code that does actual update.

This is used by following patch for IRQ_TIME_ACCOUNTING,
which has different identification logic and same update logic.

Tested-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292980144-28796-4-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 31 insertions, 15 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 8b89b3bba565..e3fa92106ed7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3568,6 +3568,32 @@ static void account_guest_time(struct task_struct *p, cputime_t cputime,
 }
 
 /*
+ * Account system cpu time to a process and desired cpustat field
+ * @p: the process that the cpu time gets accounted to
+ * @cputime: the cpu time spent in kernel space since the last update
+ * @cputime_scaled: cputime scaled by cpu frequency
+ * @target_cputime64: pointer to cpustat field that has to be updated
+ */
+static inline
+void __account_system_time(struct task_struct *p, cputime_t cputime,
+                        cputime_t cputime_scaled, cputime64_t *target_cputime64)
+{
+        cputime64_t tmp = cputime_to_cputime64(cputime);
+
+        /* Add system time to process. */
+        p->stime = cputime_add(p->stime, cputime);
+        p->stimescaled = cputime_add(p->stimescaled, cputime_scaled);
+        account_group_system_time(p, cputime);
+
+        /* Add system time to cpustat. */
+        *target_cputime64 = cputime64_add(*target_cputime64, tmp);
+        cpuacct_update_stats(p, CPUACCT_STAT_SYSTEM, cputime);
+
+        /* Account for system time used */
+        acct_update_integrals(p);
+}
+
+/*
  * Account system cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @hardirq_offset: the offset to subtract from hardirq_count()
@@ -3578,31 +3604,21 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
                          cputime_t cputime, cputime_t cputime_scaled)
 {
         struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
-        cputime64_t tmp;
+        cputime64_t *target_cputime64;
 
         if ((p->flags & PF_VCPU) && (irq_count() - hardirq_offset == 0)) {
                 account_guest_time(p, cputime, cputime_scaled);
                 return;
         }
 
-        /* Add system time to process. */
-        p->stime = cputime_add(p->stime, cputime);
-        p->stimescaled = cputime_add(p->stimescaled, cputime_scaled);
-        account_group_system_time(p, cputime);
-
-        /* Add system time to cpustat. */
-        tmp = cputime_to_cputime64(cputime);
         if (hardirq_count() - hardirq_offset)
-                cpustat->irq = cputime64_add(cpustat->irq, tmp);
+                target_cputime64 = &cpustat->irq;
         else if (in_serving_softirq())
-                cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
+                target_cputime64 = &cpustat->softirq;
         else
-                cpustat->system = cputime64_add(cpustat->system, tmp);
+                target_cputime64 = &cpustat->system;
 
-        cpuacct_update_stats(p, CPUACCT_STAT_SYSTEM, cputime);
-
-        /* Account for system time used */
-        acct_update_integrals(p);
+        __account_system_time(p, cputime, cputime_scaled, target_cputime64);
 }
 
 /*