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SubjectRe: possible migration bug with hotplug cpu
So, I found the problem.

These fields are currently not initialized upon fork. I noted that when I
updated to 2.6.31-rc2; commit 6c594c21fcb02c662f11c97be4d7d2b73060a205 was
merged into kernel by Ingo (not present yet in 2.6.30), but it only initializes
nr_migrations. Why the other fields are not initialized to 0? Even when there
are more processors, these fields may be wrong if not zeroed when a new task
is started. Below the fast way to fix it. This fixed the counters for me.

What do you think of creating a struct sched_statistics embedded into
sched_entity so we coudl memset it to zero all at once? All fields of
SCHED_STATS piece should be initialized, right?

Lucas De Marchi


diff --git a/kernel/sched.c b/kernel/sched.c
index fd3ac58..b8d75cf 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2572,15 +2572,37 @@ static void __sched_fork(struct task_struct *p)
p->se.avg_wakeup = sysctl_sched_wakeup_granularity;

#ifdef CONFIG_SCHEDSTATS
- p->se.wait_start = 0;
- p->se.sum_sleep_runtime = 0;
- p->se.sleep_start = 0;
- p->se.block_start = 0;
- p->se.sleep_max = 0;
- p->se.block_max = 0;
- p->se.exec_max = 0;
- p->se.slice_max = 0;
- p->se.wait_max = 0;
+ p->se.wait_start = 0;
+ p->se.wait_max = 0;
+ p->se.wait_count = 0;
+ p->se.wait_sum = 0;
+
+ p->se.sleep_start = 0;
+ p->se.sleep_max = 0;
+ p->se.sum_sleep_runtime = 0;
+
+ p->se.block_start = 0;
+ p->se.block_max = 0;
+ p->se.exec_max = 0;
+ p->se.slice_max = 0;
+
+ p->se.nr_migrations_cold = 0;
+ p->se.nr_failed_migrations_affine = 0;
+ p->se.nr_failed_migrations_running = 0;
+ p->se.nr_failed_migrations_hot = 0;
+ p->se.nr_forced_migrations = 0;
+ p->se.nr_forced2_migrations = 0;
+
+ p->se.nr_wakeups = 0;
+ p->se.nr_wakeups_sync = 0;
+ p->se.nr_wakeups_migrate = 0;
+ p->se.nr_wakeups_local = 0;
+ p->se.nr_wakeups_remote = 0;
+ p->se.nr_wakeups_affine = 0;
+ p->se.nr_wakeups_affine_attempts = 0;
+ p->se.nr_wakeups_passive = 0;
+ p->se.nr_wakeups_idle = 0;
+
#endif

INIT_LIST_HEAD(&p->rt.run_list);

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