rcu_prempt stalls / lockup

From: Dave Jones
Date: Mon Mar 31 2014 - 19:03:02 EST


You can tell the merge window is open, because I'm back to breaking RCU.

[ 1023.934532] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1023.935501] (detected by 0, t=6502 jiffies, g=28666, c=28665, q=0)
[ 1023.936299] INFO: Stall ended before state dump start
[ 1218.871404] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1218.872399] (detected by 0, t=26007 jiffies, g=28666, c=28665, q=0)
[ 1218.873256] INFO: Stall ended before state dump start
[ 1413.808406] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1413.809387] (detected by 0, t=45512 jiffies, g=28666, c=28665, q=0)
[ 1413.810113] INFO: Stall ended before state dump start
[ 1608.745637] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1608.746614] (detected by 0, t=65017 jiffies, g=28666, c=28665, q=0)
[ 1608.747327] INFO: Stall ended before state dump start
[ 1803.682892] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1803.683876] (detected by 1, t=84522 jiffies, g=28666, c=28665, q=0)
[ 1803.684741] INFO: Stall ended before state dump start
[ 1998.620169] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1998.621123] (detected by 0, t=104027 jiffies, g=28666, c=28665, q=0)
[ 1998.621916] INFO: Stall ended before state dump start
[ 2193.557459] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 2193.558425] (detected by 0, t=123532 jiffies, g=28666, c=28665, q=0)
[ 2193.559248] INFO: Stall ended before state dump start
[ 2388.494719] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 2388.495688] (detected by 0, t=143037 jiffies, g=28666, c=28665, q=0)
[ 2388.496417] INFO: Stall ended before state dump start
[ 2583.431983] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 2583.432967] (detected by 0, t=162542 jiffies, g=28666, c=28665, q=0)
[ 2583.433852] INFO: Stall ended before state dump start
[ 2778.369242] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 2778.370235] (detected by 0, t=182047 jiffies, g=28666, c=28665, q=0)
[ 2778.371037] INFO: Stall ended before state dump start
[ 2973.306537] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 2973.307540] (detected by 0, t=201552 jiffies, g=28666, c=28665, q=0)
[ 2973.308347] INFO: Stall ended before state dump start
[ 3168.244036] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 3168.245056] (detected by 0, t=221057 jiffies, g=28666, c=28665, q=0)
[ 3168.245805] INFO: Stall ended before state dump start
[ 3363.181458] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 3363.182496] (detected by 0, t=240562 jiffies, g=28666, c=28665, q=0)
[ 3363.183289] INFO: Stall ended before state dump start
[ 3558.118835] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 3558.119879] (detected by 0, t=260067 jiffies, g=28666, c=28665, q=0)
[ 3558.120739] INFO: Stall ended before state dump start

at that point, userspace stopped responding. cursor on console was blinking,
but I couldn't even switch tty's, or sysrq dump.

rc8 was fine, so this is todays rcu changes.

Dave

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