Re: rtai task causes rcu problems on exit

Correction, they occur the entire time the real time task is running. Is 
there a way to disable this somehow or configure it so it is ignored. It 
is cause multi-second delays in the execution of other programs running 
on the same system as the real-time task.


On 3/12/2016 19:52, JB wrote:
> Hi,
> I'm a little confused about some behavior I'm currently seeing after 
> upgrading to kernel 3.18.22 and RTAI 5.0-test1. After my real-time 
> task ends the first, time all seems fine. However, if I start it up a 
> second time, then stop it, it doesn't stop for a while. After a while, 
> it stops and the messages below show up in the logs. Is RTAI 
> conflicting in some way with this new RCU feature of the kernel?
>
>
> Mar 12 11:56:00 localhost kernel: [  249.450228] INFO: rcu_preempt 
> detected stalls on CPUs/tasks: {} (detected by 0, t=21104 jiffies, 
> g=11573, c=11572, q=30
> Mar 12 11:56:00 localhost kernel: [  249.450234] INFO: Stall ended 
> before state dump start
> Mar 12 11:56:00 localhost kernel: INFO: rcu_preempt detected stalls on 
> CPUs/tasks: {} (detected by 0, t=21104 jiffies, g=11573, c=11572, q=3068)
> Mar 12 11:56:00 localhost kernel: INFO: Stall ended before state dump 
> start
> Mar 12 11:56:22 localhost kernel: [  271.625505] INFO: rcu_preempt 
> detected stalls on CPUs/tasks: { 1} (detected by 0, t=21524 jiffies, 
> g=11575, c=11574, q=
> Mar 12 11:56:22 localhost kernel: [  271.625511] Task dump for CPU 1:
> Mar 12 11:56:22 localhost kernel: [  271.625512] swapper/1       R 
> running task    12624     0      1 0x00200000
> Mar 12 11:56:22 localhost kernel: [  271.625516]  ffff880077417d00 
> 0000000000000082 0000000000000000 0000000000000000
> Mar 12 11:56:22 localhost kernel: [  271.625519]  ffff880037096300 
> ffff880079fcda00 00000000fffffffa ffffc90004704230
> Mar 12 11:56:22 localhost kernel: [  271.625521]  ffffffffa0170e80 
> ffffffffa0170e80 0000000000000001 ffffffffa01b5708
> Mar 12 11:56:22 localhost kernel: [  271.625524] Call Trace:
> Mar 12 11:56:22 localhost kernel: [  271.625530] [<ffffffffa015ed27>] 
> rt_timer_handler+0x477/0x7e0 [rtai_sched]
> Mar 12 11:56:22 localhost kernel: [  271.625532] [<ffffffffa015da1a>] 
> rtai_hirq_dispatcher+0x6a/0x1c0 [rtai_sched]
> Mar 12 11:56:22 localhost kernel: [  271.625536] [<ffffffff810d63f3>] 
> __ipipe_dispatch_irq+0xd3/0x1b0
> Mar 12 11:56:22 localhost kernel: [  271.625539] [<ffffffff81031503>] 
> __ipipe_handle_irq+0x73/0x190
> Mar 12 11:56:22 localhost kernel: [  271.625542] [<ffffffff816a16c0>] 
> apic_timer_interrupt+0x60/0x90
> Mar 12 11:56:22 localhost kernel: [  271.625544] [<ffffffff813192f3>] 
> ? __this_cpu_preempt_check+0x13/0x20
> Mar 12 11:56:22 localhost kernel: [  271.625593] [<ffffffffa180cd60>] 
> ? _nv008584rm+0x90/0x3e0 [nvidia]
> Mar 12 11:56:22 localhost kernel: [  271.625596] [<ffffffff810919d0>] 
> ? rcu_eqs_enter_common.isra.43+0x60/0x120
> Mar 12 11:56:22 localhost kernel: [  271.625598] [<ffffffff813192d7>] 
> ? debug_smp_processor_id+0x17/0x20
> Mar 12 11:56:22 localhost kernel: [  271.625601] [<ffffffff8100c540>] 
> ? mwait_idle+0x60/0xa0
> Mar 12 11:56:22 localhost kernel: [  271.625603] [<ffffffff8100d0ba>] 
> arch_cpu_idle+0xa/0x10
> Mar 12 11:56:22 localhost kernel: [  271.625606] [<ffffffff810826a9>] 
> cpu_startup_entry+0x319/0x470
> Mar 12 11:56:22 localhost kernel: [  271.625609] [<ffffffff810a5807>] 
> ? clockevents_config_and_register+0x27/0x30
> Mar 12 11:56:22 localhost kernel: [  271.625611] [<ffffffff81032473>] 
> start_secondary+0x143/0x150
> Mar 12 11:56:22 localhost kernel: INFO: rcu_preempt detected stalls on 
> CPUs/tasks: { 1} (detected by 0, t=21524 jiffies, g=11575, c=11574, 
> q=1230)
> Mar 12 11:56:22 localhost kernel: Task dump for CPU 1:
> Mar 12 11:56:22 localhost kernel: swapper/1       R  running task 
> 12624     0      1 0x00200000
> Mar 12 11:56:22 localhost kernel: ffff880077417d00 0000000000000082 
> 0000000000000000 0000000000000000
> Mar 12 11:56:22 localhost kernel: ffff880037096300 ffff880079fcda00 
> 00000000fffffffa ffffc90004704230
> Mar 12 11:56:22 localhost kernel: ffffffffa0170e80 ffffffffa0170e80 
> 0000000000000001 ffffffffa01b5708
> Mar 12 11:56:22 localhost kernel: Call Trace:
> Mar 12 11:56:22 localhost kernel: [<ffffffffa015ed27>] 
> rt_timer_handler+0x477/0x7e0 [rtai_sched]
> Mar 12 11:56:22 localhost kernel: [<ffffffffa015da1a>] 
> rtai_hirq_dispatcher+0x6a/0x1c0 [rtai_sched]
> Mar 12 11:56:22 localhost kernel: [<ffffffff810d63f3>] 
> __ipipe_dispatch_irq+0xd3/0x1b0
> Mar 12 11:56:22 localhost kernel: [<ffffffff81031503>] 
> __ipipe_handle_irq+0x73/0x190
> Mar 12 11:56:22 localhost kernel: [<ffffffff816a16c0>] 
> apic_timer_interrupt+0x60/0x90
> Mar 12 11:56:22 localhost kernel: [<ffffffff813192f3>] ? 
> __this_cpu_preempt_check+0x13/0x20
> Mar 12 11:56:22 localhost kernel: [<ffffffffa180cd60>] ? 
> _nv008584rm+0x90/0x3e0 [nvidia]
> Mar 12 11:56:22 localhost kernel: [<ffffffff810919d0>] ? 
> rcu_eqs_enter_common.isra.43+0x60/0x120
> Mar 12 11:56:22 localhost kernel: [<ffffffff813192d7>] ? 
> debug_smp_processor_id+0x17/0x20
> Mar 12 11:56:22 localhost kernel: [<ffffffff8100c540>] ? 
> mwait_idle+0x60/0xa0
> Mar 12 11:56:22 localhost kernel: [<ffffffff8100d0ba>] 
> arch_cpu_idle+0xa/0x10
> Mar 12 11:56:22 localhost kernel: [<ffffffff810826a9>] 
> cpu_startup_entry+0x319/0x470
> Mar 12 11:56:22 localhost kernel: [<ffffffff810a5807>] ? 
> clockevents_config_and_register+0x27/0x30
> Mar 12 11:56:22 localhost kernel: [<ffffffff81032473>] 
> start_secondary+0x143/0x150
>
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