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sched: Sanitize fork() handling

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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>
This commit is contained in:
Peter Zijlstra 2009-11-27 17:32:46 +01:00 • committed by Ingo Molnar
parent ab19cb2331
commit cd29fe6f26
3 changed files with 34 additions and 43 deletions
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47
kernel/sched.c
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@ -1811,6 +1811,20 @@ static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
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 @@ inline int task_curr(const struct task_struct *p)
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 @@ static void __sched_fork(struct task_struct *p)
void sched_fork(struct task_struct *p, int clone_flags)
{
int cpu = get_cpu();
unsigned long flags;
__sched_fork(p);
@ -2586,13 +2585,13 @@ void sched_fork(struct task_struct *p, int clone_flags)
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 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
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