[PATCH] sched: consolidate sbe sbf
Consolidate balance-on-exec with balance-on-fork. This is made easy by the
sched-domains RCU patches.
As well as the general goodness of code reduction, this allows the runqueues
to be unlocked during balance-on-fork.
schedstats is a problem. Maybe just have balance-on-event instead of
distinguishing fork and exec?
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index a28d11e..2c78068 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1003,9 +1003,6 @@
p->pdeath_signal = 0;
p->exit_state = 0;
- /* Perform scheduler related setup */
- sched_fork(p);
-
/*
* Ok, make it visible to the rest of the system.
* We dont wake it up yet.
@@ -1014,18 +1011,24 @@
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
+ /* Perform scheduler related setup. Assign this task to a CPU. */
+ sched_fork(p, clone_flags);
+
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);
/*
- * The task hasn't been attached yet, so cpus_allowed mask cannot
- * have changed. The cpus_allowed mask of the parent may have
- * changed after it was copied first time, and it may then move to
- * another CPU - so we re-copy it here and set the child's CPU to
- * the parent's CPU. This avoids alot of nasty races.
+ * The task hasn't been attached yet, so its cpus_allowed mask will
+ * not be changed, nor will its assigned CPU.
+ *
+ * The cpus_allowed mask of the parent may have changed after it was
+ * copied first time - so re-copy it here, then check the child's CPU
+ * to ensure it is on a valid CPU (and if not, just force it back to
+ * parent's CPU). This avoids alot of nasty races.
*/
p->cpus_allowed = current->cpus_allowed;
- set_task_cpu(p, smp_processor_id());
+ if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed)))
+ set_task_cpu(p, smp_processor_id());
/*
* Check for pending SIGKILL! The new thread should not be allowed