Commit-ID: e99e955b90d7aaa4418cace9734e8069921ba440 Gitweb: http://git.kernel.org/tip/e99e955b90d7aaa4418cace9734e8069921ba440 Author: Ingo Molnar <mingo@xxxxxxx> AuthorDate: Mon, 15 Oct 2012 07:46:28 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Thu, 18 Oct 2012 08:08:24 +0200 numa: Fix task_work() double add task_work() must not be double added - it can result in an infinite loop in run_task_work(). So separate out p->numa_work and signal an 'empty' work callback with numa_work->next == &numa_work. (NULL cannot be used as the task work code uses it.) It would be handy if kerne/task_work.c had something like this in run_task_work(): if (WARN_ON_ONCE(work->next == work)) break; As it took some time to figure out why it was sporadically hanging. Signed-off-by: Ingo Molnar <mingo@xxxxxxx> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Link: http://lkml.kernel.org/n/tip-gT2keodfehhzwmx0appafeUy@xxxxxxxxxxxxxx --- include/linux/sched.h | 1 + kernel/sched/core.c | 1 + kernel/sched/fair.c | 16 ++++++---------- 3 files changed, 8 insertions(+), 10 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index c86db44..7882686 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1529,6 +1529,7 @@ struct task_struct { u64 node_stamp; /* migration stamp */ unsigned long numa_contrib; unsigned long *numa_faults; + struct callback_head numa_work; #endif /* CONFIG_SCHED_NUMA */ struct rcu_head rcu; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 23ad8b9..08661fe 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1546,6 +1546,7 @@ static void __sched_fork(struct task_struct *p) p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0; p->numa_faults = NULL; p->numa_task_period = sysctl_sched_numa_task_period_min; + p->numa_work.next = &p->numa_work; #endif /* CONFIG_SCHED_NUMA */ } diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 530448c..1e24aa1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -900,8 +900,9 @@ void task_numa_work(struct callback_head *work) struct task_struct *p = current; struct mm_struct *mm = p->mm; - WARN_ON_ONCE(p != container_of(work, struct task_struct, rcu)); + WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work)); + work->next = work; /* protect against double add */ /* * Who cares about NUMA placement when they're dying. * @@ -933,12 +934,13 @@ void task_numa_work(struct callback_head *work) */ void task_tick_numa(struct rq *rq, struct task_struct *curr) { + struct callback_head *work = &curr->numa_work; u64 period, now; /* * We don't care about NUMA placement if we don't have memory. */ - if (!curr->mm) + if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) return; /* @@ -954,14 +956,8 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr) curr->node_stamp = now; if (!time_before(jiffies, curr->mm->numa_next_scan)) { - /* - * We can re-use curr->rcu because we checked curr->mm - * != NULL so release_task()->call_rcu() was not called - * yet and exit_task_work() is called before - * exit_notify(). - */ - init_task_work(&curr->rcu, task_numa_work); - task_work_add(curr, &curr->rcu, true); + init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */ + task_work_add(curr, work, true); } } } -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html