Messages in this thread | | | Date | Mon, 16 Jun 2014 09:30:36 +0800 | From | Lai Jiangshan <> | Subject | Re: workqueue: WARN at at kernel/workqueue.c:2176 |
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Hi, Peter
Ping...
thanks, Lai
On 06/10/2014 09:21 AM, Lai Jiangshan wrote: > On 06/09/2014 10:01 PM, Jason J. Herne wrote: >> On 06/05/2014 06:54 AM, Lai Jiangshan wrote: >>> ------------ >>> >>> Subject: [PATCH] sched: migrate the waking tasks >>> >>> Current code skips to migrate the waking task silently when TTWU_QUEUE is enabled. >>> >>> When a task is waking, it is pending on the wake_list of the rq, but >>> it is not on queue (task->on_rq == 0). In this case, set_cpus_allowed_ptr() >>> and __migrate_task() will not migrate it due to it is not on queue. >>> >>> This behavior is incorrect, because the task had been already waken-up, it will >>> be running on the wrong CPU without correct placement until the next wake-up >>> or update for cpus_allowed. >>> >>> To fix this problem, we need to make the waking tasks on-queue (transfer >>> the waking tasks to running state) before migrate them. >>> >>> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> >>> --- >>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >>> index 268a45e..d05a5a1 100644 >>> --- a/kernel/sched/core.c >>> +++ b/kernel/sched/core.c >>> @@ -1474,20 +1474,24 @@ static int ttwu_remote(struct task_struct *p, int wake_flags) >>> } >>> >>> #ifdef CONFIG_SMP >>> -static void sched_ttwu_pending(void) >>> +static void sched_ttwu_pending_locked(struct rq *rq) >>> { >>> - struct rq *rq = this_rq(); >>> struct llist_node *llist = llist_del_all(&rq->wake_list); >>> struct task_struct *p; >>> >>> - raw_spin_lock(&rq->lock); >>> - >>> while (llist) { >>> p = llist_entry(llist, struct task_struct, wake_entry); >>> llist = llist_next(llist); >>> ttwu_do_activate(rq, p, 0); >>> } >>> +} >>> >>> +static void sched_ttwu_pending(void) >>> +{ >>> + struct rq *rq = this_rq(); >>> + >>> + raw_spin_lock(&rq->lock); >>> + sched_ttwu_pending_locked(rq); >>> raw_spin_unlock(&rq->lock); >>> } >>> >>> @@ -4530,6 +4534,11 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) >>> goto out; >>> >>> dest_cpu = cpumask_any_and(cpu_active_mask, new_mask); >>> + >>> + /* Ensure it is on rq for migration if it is waking */ >>> + if (p->state == TASK_WAKING) >>> + sched_ttwu_pending_locked(rq); >>> + >>> if (p->on_rq) { >>> struct migration_arg arg = { p, dest_cpu }; >>> /* Need help from migration thread: drop lock and wait. */ >>> @@ -4576,6 +4585,10 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) >>> if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p))) >>> goto fail; >>> >>> + /* Ensure it is on rq for migration if it is waking */ >>> + if (p->state == TASK_WAKING) >>> + sched_ttwu_pending_locked(rq_src); >>> + >>> /* >>> * If we're not on a rq, the next wake-up will ensure we're >>> * placed properly. >>> >> >> FYI, this patch appears to fix the problem. I was able to run for 3 days without hitting the warning. > > Thank you for the test. It proves that we found the root cause. > Your tests are the most important, coding takes the second place, let it go forward step by step. > > Thanks, > Lai > >> >> I see that you guys are still discussing the details of the fix. When you decide on a final solution I'm happy to retest. Just be sure to ask :). It is hard to tell what to test with so many patches and code snippets flying around all the time. >> >> Happy coding. >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > . >
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