Commit-ID: bac7857319bcf7fed329a10bb760053e761115c0
Gitweb: http://git.kernel.org/tip/bac7857319bcf7fed329a10bb760053e761115c0
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Wed, 18 May 2016 21:57:33 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 3 Jun 2016 09:18:58 +0200
sched/fair: Use task_rcu_dereference()
Simplify task_numa_compare()'s task reference magic by using
task_rcu_dereference().
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Cc: Kirill Tkhai <tkhai@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20160518195733.GA15914@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 34 ++++------------------------------
1 file changed, 4 insertions(+), 30 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1e87bb6..c6dd8ba 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -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,
--
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