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sched/fair: Use task_rcu_dereference()

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Simplify task_numa_compare()'s task reference magic by using
task_rcu_dereference().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Link: http://lkml.kernel.org/r/20160518195733.GA15914@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2016-05-18 21:57:33 +02:00 committed by Ingo Molnar
parent 150593bf86
commit bac7857319
1 changed files with 4 additions and 30 deletions
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34
kernel/sched/fair.c
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@ -1305,6 +1305,8 @@ static void task_numa_assign(struct task_numa_env *env,
{
if (env->best_task)
put_task_struct(env->best_task);
if (p)
get_task_struct(p);
env->best_task = p;
env->best_imp = imp;
@ -1372,31 +1374,11 @@ static void task_numa_compare(struct task_numa_env *env,
long imp = env->p->numa_group ? groupimp : taskimp;
long moveimp = imp;
int dist = env->dist;
bool assigned = false;
rcu_read_lock();
raw_spin_lock_irq(&dst_rq->lock);
cur = dst_rq->curr;
/*
* No need to move the exiting task or idle task.
*/
if ((cur->flags & PF_EXITING) || is_idle_task(cur))
cur = task_rcu_dereference(&dst_rq->curr);
if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
cur = NULL;
else {
/*
* The task_struct must be protected here to protect the
* p->numa_faults access in the task_weight since the
* numa_faults could already be freed in the following path:
* finish_task_switch()
* --> put_task_struct()
* --> __put_task_struct()
* --> task_numa_free()
*/
get_task_struct(cur);
}
raw_spin_unlock_irq(&dst_rq->lock);
/*
* Because we have preemption enabled we can get migrated around and
@ -1479,7 +1461,6 @@ balance:
*/
if (!load_too_imbalanced(src_load, dst_load, env)) {
imp = moveimp - 1;
put_task_struct(cur);
cur = NULL;
goto assign;
}
@ -1505,16 +1486,9 @@ balance:
env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
assign:
assigned = true;
task_numa_assign(env, cur, imp);
unlock:
rcu_read_unlock();
/*
* The dst_rq->curr isn't assigned. The protection for task_struct is
* finished.
*/
if (cur && !assigned)
put_task_struct(cur);
}
static void task_numa_find_cpu(struct task_numa_env *env,