Re: rcu_prempt stalls / lockup

[Dave Jones <davej@redhat.com>]

On Tue, Apr 01, 2014 at 08:30:32AM -0700, Paul E. McKenney wrote:
 > > [14403.765300] INFO: rcu_preempt detected stalls on CPUs/tasks:
 > > [14403.766405]  (detected by 0, t=260067 jiffies, g=449892, c=449891, q=0)
 > > and on and on..
 > > 
 > > so kernel space still works like before, but userspace is locked up.
 > 
 > Interesting.  I suspect that if you reverted the rest of this merge
 > window's RCU patches, you would get the same result.
 > 
 > >  > If that doesn't work, I will need to put together some diagnostic patches.
 > >  > Starting with the one below.
 > > 
 > > bugger, I forgot to apply this last night. I'll do it on the next run.
 > 
 > But let's see what this shows first.

[ 1173.923463] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1173.924457] 	(detected by 0, t=6502 jiffies, g=47728, c=47727, q=0)
[ 1173.925199] INFO: Stall ended before state dump start, gp_kthread state: 0x2
[ 1368.859744] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1368.860754] 	(detected by 0, t=26007 jiffies, g=47728, c=47727, q=0)
[ 1368.861559] INFO: Stall ended before state dump start, gp_kthread state: 0x2
[ 1563.796416] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1563.797426] 	(detected by 0, t=45512 jiffies, g=47728, c=47727, q=0)
[ 1563.798293] INFO: Stall ended before state dump start, gp_kthread state: 0x2
[ 1758.733747] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1758.734725] 	(detected by 0, t=65017 jiffies, g=47728, c=47727, q=0)
[ 1758.735526] INFO: Stall ended before state dump start, gp_kthread state: 0x2
[ 1953.670944] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1953.671932] 	(detected by 0, t=84522 jiffies, g=47728, c=47727, q=0)
[ 1953.672735] INFO: Stall ended before state dump start, gp_kthread state: 0x2
[ 2148.608132] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 2148.609140] 	(detected by 0, t=104027 jiffies, g=47728, c=47727, q=0)
etc etc.

	Dave