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SubjectRe: linux-next: Tree for May 26 (RCU stalls)
On Thu, May 26, 2011 at 05:48:32PM +0200, Sedat Dilek wrote:
> On Thu, May 26, 2011 at 8:39 AM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > Hi all,
> >
> > [The kernel.org mirroring is being slow today]
> >
> > Changes since 20110525:
> >
> > Linus' tree gained a build failure for which I applied a patch.
> >
> > The m68knommu tree lost its conflicts.
> >
> > The hwmon-staging lost its conflict.
> >
> > The wireless lost its conflict.
> >
> > The mmc lost its conflict.
> >
> > The dwmw2-iommu tree lost its conflict.
> >
> > The kvm tree still had its build failure so I used the version from
> > next-20110524.
> >
> > The namespace lost its conflicts.
> >
> > ----------------------------------------------------------------------------
> >
>
> Hi,
>
> I see these call-traces on x86 UP machine:
>
> [ 240.268061] INFO: task rcun0:8 blocked for more than 120 seconds.
> [ 240.268069] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
> [ 240.268072] rcun0 D 00000000 0 8 2 0x00000000
> [ 240.268079] f6473fb8 00000046 013131b6 00000000 c1461ac0 00000000
> 00000000 c1461ac0
> [ 240.268089] 00000000 00000000 f645dc70 f645bf60 00000003 f6473f78
> c102a570 f6473f9c
> [ 240.268097] c1021476 00000000 f645bf6c 00000001 00000000 00000286
> f6473f9c c129b35a
> [ 240.268106] Call Trace:
> [ 240.268121] [<c102a570>] ? default_wake_function+0xb/0xd
> [ 240.268127] [<c1021476>] ? __wake_up_common+0x33/0x5b
> [ 240.268134] [<c129b35a>] ? _raw_spin_unlock_irqrestore+0xe/0x10
> [ 240.268140] [<c10234ed>] ? complete+0x34/0x3e
> [ 240.268147] [<c1074d23>] ? cpumask_weight+0xc/0xc
> [ 240.268157] [<c1044c97>] kthread+0x53/0x67
> [ 240.268162] [<c1044c44>] ? kthread_worker_fn+0x111/0x111
> [ 240.268169] [<c12a123e>] kernel_thread_helper+0x6/0xd
>
> dmesg and kernel-config are attached.

Hello, Sedat,

Does the following patch clear things up?

Thanx, Paul

------------------------------------------------------------------------

rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state

Upon creation, kthreads are in TASK_UNINTERRUPTIBLE state, which can
result in softlockup warnings. Because some of RCU's kthreads can
legitimately be idle indefinitely, start them in TASK_INTERRUPTIBLE
state in order to avoid those warnings.

Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Yinghai Lu <yinghai@kernel.org>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index a1a8bb6..40aab8d 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1647,6 +1647,7 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
if (IS_ERR(t))
return PTR_ERR(t);
kthread_bind(t, cpu);
+ set_task_state(t, TASK_INTERRUPTIBLE);
per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
per_cpu(rcu_cpu_kthread_task, cpu) = t;
@@ -1754,6 +1755,7 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
if (IS_ERR(t))
return PTR_ERR(t);
raw_spin_lock_irqsave(&rnp->lock, flags);
+ set_task_state(t, TASK_INTERRUPTIBLE);
rnp->node_kthread_task = t;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
sp.sched_priority = 99;
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 049f278..a767b7d 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1295,6 +1295,7 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
if (IS_ERR(t))
return PTR_ERR(t);
raw_spin_lock_irqsave(&rnp->lock, flags);
+ set_task_state(t, TASK_INTERRUPTIBLE);
rnp->boost_kthread_task = t;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
sp.sched_priority = RCU_KTHREAD_PRIO;

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