Re: kernel BUG at kernel/sched_rt.c:493!

[Mike Galbraith]

On Fri, 2013-01-11 at 06:22 +0100, Mike Galbraith wrote: 
> On Thu, 2013-01-10 at 13:58 -0600, Shawn Bohrer wrote:
> 
> > Here is the output:
> > 
> > [   81.278842] SysRq : Changing Loglevel
> > [   81.279027] Loglevel set to 9
> > [   83.285456] Initial want: 50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 900000000
> > [   85.286452] Initial want: 50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 900000000
> > [   85.289625] Initial want: 50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 900000000
> > [   87.287435] Initial want: 100000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 850000000
> > [   87.290718] Initial want: 50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 900000000
> > [   89.288469] Initial want: -50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 1000000000
> > [   89.291550] Initial want: 150000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 800000000
> > [   89.292940] Initial want: 100000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 850000000
> > [   89.294082] Initial want: 100000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 850000000
> > [   89.295194] Initial want: 50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 900000000
> > [   89.296274] Initial want: 50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 900000000
> > [   90.959004] [sched_delayed] sched: RT throttling activated
> > [   91.289470] Initial want: 200000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 750000000
> > [   91.292767] Initial want: 200000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 750000000
> > [   91.294037] Initial want: 200000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 750000000
> > [   91.295364] Initial want: 200000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 750000000
> > [   91.296355] BUG triggered, want: 200000000
> > [   91.296355] 
> > [   91.296355] rt_rq[7]:
> > [   91.296355]   .rt_nr_running                 : 0
> > [   91.296355]   .rt_throttled                  : 0
> > [   91.296355]   .rt_time                       : 0.000000
> > [   91.296355]   .rt_runtime                    : 750.000000
> > [   91.307332] Initial want: -50000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 1000000000
> > [   91.308440] Initial want: -100000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 1050000000
> > [   91.309586] Initial want: -150000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 1100000000
> > [   91.310716] Initial want: -200000000 rt_b->rt_runtime: 950000000 rt_rq->rt_runtime: 1150000000
> > [   91.311707] BUG triggered, want: -200000000
> > [   91.311707] 
> > [   91.311707] rt_rq[6]:
> > [   91.311707]   .rt_nr_running                 : 1
> > [   91.311707]   .rt_throttled                  : 0
> > [   91.311707]   .rt_time                       : 307.209987
> > [   91.311707]   .rt_runtime                    : 1150.000000
> 
> That makes about as much sense as my crash did.  There is no leak, but
> cpu found nada.  So rd/span is changing on us?

So I looked at the locking (yet again), and (for the umpteenth time) see
no way in the world that can happen.  Hrmph.

-Mike

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