Messages in this thread Patch in this message | | | Date | Tue, 22 Dec 2009 15:19:44 +0800 | Subject | Re: 2.6.33-rc1 unusable due to scheduler issues, circular locking, WARNs and BUGs | From | Américo Wang <> |
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[Fix top-posting]
On Tue, Dec 22, 2009 at 1:42 PM, Xiaotian Feng <xtfeng@gmail.com> wrote: > > On Tue, Dec 22, 2009 at 8:17 AM, Eric Paris <eparis@redhat.com> wrote: >> Trying to build a kernel on a 48 core x86_64 box using make -j 64 and >> I'm exploding in the scheduler. I'm running (and building) kernel >> f7b84a6ba7eaeba4e1df8feddca1473a7db369a5 There are three distinct >> signatures of problems. Some boots I'll see all 3 of these failures >> sometimes only 1 or 2 of them. That's the reason they are kinda split >> up in dmesg. >> >> 1) gcc/3141 is trying to acquire lock: >> (&(&sem->wait_lock)->rlock){......}, at: [<ffffffff81223234>] __down_read_trylock+0x13/0x46 >> >> but task is already holding lock: >> (&rq->lock){-.-.-.}, at: [<ffffffff8103dd2d>] task_rq_lock+0x51/0x83 >> >> 2) WARN() in kernel/sched_fair.c:1001 hrtick_start_fair() >> >> 3) NULL pointer dereference at 0000000000000168 in check_preempt_wakeup >> kernel/sched_fair.c >> >> Full backtraces are in the attached dmesg. >> > Does a revert of cd29fe6f2637cc2ccbda5ac65f5332d6bf5fa3c6 fix this problem?
I don't think so...
I think the most suspicious commit here is ab19cb23. It kicked "local_irq_save()" out, which means if the task is selected to run on another cpu which doesn't disable irq, we will have a page fault, thun we will try to hold mm->mmap_sem while we are holding rq->lock already.
Does the following untested patch fix the problem?
NOT-signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
------ diff --git a/kernel/sched.c b/kernel/sched.c index 87f1f47..221ab59 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2408,13 +2408,13 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, if (p->sched_class->task_waking) p->sched_class->task_waking(rq, p);
- __task_rq_unlock(rq); + task_rq_unlock(rq);
cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags); if (cpu != orig_cpu) set_task_cpu(p, cpu);
- rq = __task_rq_lock(p); + rq = task_rq_lock(p); update_rq_clock(rq);
WARN_ON(p->state != TASK_WAKING); -- 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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