Commit-ID: bac7857319bcf7fed329a10bb760053e761115c0 Gitweb: http://git.kernel.org/tip/bac7857319bcf7fed329a10bb760053e761115c0 Author: Oleg Nesterov <[email protected]> AuthorDate: Wed, 18 May 2016 21:57:33 +0200 Committer: Ingo Molnar <[email protected]> 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 <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Kirill Tkhai <[email protected]> Cc: Kirill Tkhai <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vladimir Davydov <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- 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,
