sched: Sanitize fork() handling
Currently we try to do task placement in wake_up_new_task() after we do
the load-balance pass in sched_fork(). This yields complicated semantics
in that we have to deal with tasks on different RQs and the
set_task_cpu() calls in copy_process() and sched_fork()
Rename ->task_new() to ->task_fork() and call it from sched_fork()
before the balancing, this gives the policy a clear point to place the
task.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index c92670f..33c9035 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1811,6 +1811,20 @@
static void calc_load_account_active(struct rq *this_rq);
+static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
+{
+ set_task_rq(p, cpu);
+#ifdef CONFIG_SMP
+ /*
+ * After ->cpu is set up to a new value, task_rq_lock(p, ...) can be
+ * successfuly executed on another CPU. We must ensure that updates of
+ * per-task data have been completed by this moment.
+ */
+ smp_wmb();
+ task_thread_info(p)->cpu = cpu;
+#endif
+}
+
#include "sched_stats.h"
#include "sched_idletask.c"
#include "sched_fair.c"
@@ -1967,20 +1981,6 @@
return cpu_curr(task_cpu(p)) == p;
}
-static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
-{
- set_task_rq(p, cpu);
-#ifdef CONFIG_SMP
- /*
- * After ->cpu is set up to a new value, task_rq_lock(p, ...) can be
- * successfuly executed on another CPU. We must ensure that updates of
- * per-task data have been completed by this moment.
- */
- smp_wmb();
- task_thread_info(p)->cpu = cpu;
-#endif
-}
-
static inline void check_class_changed(struct rq *rq, struct task_struct *p,
const struct sched_class *prev_class,
int oldprio, int running)
@@ -2552,7 +2552,6 @@
void sched_fork(struct task_struct *p, int clone_flags)
{
int cpu = get_cpu();
- unsigned long flags;
__sched_fork(p);
@@ -2586,13 +2585,13 @@
if (!rt_prio(p->prio))
p->sched_class = &fair_sched_class;
+ if (p->sched_class->task_fork)
+ p->sched_class->task_fork(p);
+
#ifdef CONFIG_SMP
cpu = select_task_rq(p, SD_BALANCE_FORK, 0);
#endif
- local_irq_save(flags);
- update_rq_clock(cpu_rq(cpu));
set_task_cpu(p, cpu);
- local_irq_restore(flags);
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (likely(sched_info_on()))
@@ -2625,17 +2624,7 @@
rq = task_rq_lock(p, &flags);
BUG_ON(p->state != TASK_RUNNING);
update_rq_clock(rq);
-
- if (!p->sched_class->task_new || !current->se.on_rq) {
- activate_task(rq, p, 0);
- } else {
- /*
- * Let the scheduling class do new task startup
- * management (if any):
- */
- p->sched_class->task_new(rq, p);
- inc_nr_running(rq);
- }
+ activate_task(rq, p, 0);
trace_sched_wakeup_new(rq, p, 1);
check_preempt_curr(rq, p, WF_FORK);
#ifdef CONFIG_SMP