Hi Antonio,
On Fri, 2012-01-13 at 14:17 -0500, Antonio Barbalace wrote:
> I would like to report the following bug that is not still solved in
> the current 3.0.14 ver.
>
> [ 300.459960] BUG: sleeping function called from invalid context at
> kernel/rtm5
> [ 300.459991] in_atomic(): 1, irqs_disabled(): 128, pid: 9, name: migration/1
> [ 300.459991] 1 lock held by migration/1/9:
> [ 300.459991] #0: (tasklist_lock){++++..}, at: [<c0064fe8>]
> __cpu_disable+0x0
> [ 300.460021] irq event stamp: 1887
> [ 300.460052] hardirqs last enabled at (1886): [<c04e5878>]
> _raw_spin_unlock_8
> [ 300.460052] hardirqs last disabled at (1887): [<c00efd10>]
> stop_machine_cpu_4
> [ 300.460083] softirqs last enabled at (0): [<c009f628>]
> copy_process+0x3b4/00
> [ 300.460113] softirqs last disabled at (0): [< (null)>] (null)
> [ 300.460144] [<c00670e4>] (unwind_backtrace+0x0/0xf4) from
> [<c04e4c88>] (__rt)
> [ 300.460174] [<c04e4c88>] (__rt_spin_lock+0x18/0x2c) from
> [<c04e51e0>] (rt_re)
> [ 300.460174] [<c04e51e0>] (rt_read_lock+0x54/0x68) from [<c0064fe8>]
> (__cpu_d)
> [ 300.460235] [<c0064fe8>] (__cpu_disable+0xdc/0x170) from
> [<c04d4b7c>] (take_)
> [ 300.460235] [<c04d4b7c>] (take_cpu_down+0xc/0x30) from [<c00efd28>]
> (stop_ma)
> [ 300.460235] [<c00efd28>] (stop_machine_cpu_stop+0xd8/0x114) from
> [<c00efad4>)
> [ 300.460266] [<c00efad4>] (cpu_stopper_thread+0xb8/0x1ac) from
> [<c00c29f8>] ()
> [ 300.460327] [<c00c29f8>] (kthread+0x88/0x90) from [<c0060914>]
> (kernel_threa)
> [ 300.464385] CPU1: shutdown
>
> This is due to the following arch/arm/kernel/smp.c @ __cpu_disable code:
>
> 169 read_lock(&tasklist_lock);
> 170 for_each_process(p) {
> 171 if (p->mm)
> 172 cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
> 173 }
> 174 read_unlock(&tasklist_lock);
>
> I am not a rt expert, do you have any clue on how to solve this problem?
Hmm, I'll need to look at this code deeper. The read_lock() in -rt can
sleep, and this is being called to shutdown a CPU, which I'm sure
disables interrupts along the way.
What did you do to cause this? Does this happen when you take CPU 1
offline?
-- Steve
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