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SubjectRe: BUG: scheduling while atomic, under native_smp_prepare_cpus()
Hi Michael,

On Mon, Aug 20, 2012 at 05:20:35PM +0800, Michael Wang wrote:
> On 08/17/2012 09:49 PM, Fengguang Wu wrote:
>
> Hi, FengGuang
>
> native_smp_prepare_cpus has already disabled the preempt before
> reach __irq_alloc_descs(), and sleep in mutex_lock() cause the bug.
>
> May be the follow patch could help to solve the issue(actually I
> think the true problem should be in _cond_resched...).

Is this a debug patch? Since what it does is to conditionally disable
the warning.

> I can't do test by my self since I can't reproduce the issue on my
> machine, the kernel_init thread never got a need sched flag set at
> that moment in my case...

I'll try it and report back :)

Thanks,
Fengguang

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 4376c9f..3396c33 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3321,7 +3321,8 @@ static inline void schedule_debug(struct task_struct *prev)
> * schedule() atomically, we ignore that path for now.
> * Otherwise, whine if we are scheduling when we should not be.
> */
> - if (unlikely(in_atomic_preempt_off() && !prev->exit_state))
> + if (unlikely(in_atomic_preempt_off() && !prev->exit_state
> + && system_state == SYSTEM_RUNNING))
> __schedule_bug(prev);
> rcu_sleep_check();
>
>
> > Trace one (full config/dmesg attached):
> >
> > [ 0.042794] init IO_APIC IRQs [ 0.043305] apic 2 pin 0 not
> > connected [ 0.043953] BUG: scheduling while atomic:
> > swapper/0/1/0x10000002 [ 0.044017] no locks held by swapper/0/1. [
> > 0.044692] Pid: 1, comm: swapper/0 Not tainted
> > 3.6.0-rc1-00420-gb7aebb9 #34 [ 0.045861] Call Trace: [ 0.048071]
> > [<c106361e>] __schedule_bug+0x5e/0x70 [ 0.048890] [<c1b28701>]
> > __schedule+0x91/0xb10 [ 0.049660] [<c14472ea>] ?
> > vsnprintf+0x33a/0x450 [ 0.050444] [<c1060006>] ?
> > lg_local_lock+0x6/0x70 [ 0.051256] [<c14fb5b1>] ?
> > wait_for_xmitr+0x31/0x90 [ 0.052019] [<c144fd55>] ?
> > do_raw_spin_unlock+0xa5/0xf0 [ 0.052903] [<c1b2a532>] ?
> > _raw_spin_unlock+0x22/0x30 [ 0.053759] [<c105cdbb>] ?
> > up+0x1b/0x70 [ 0.054421] [<c1065d6b>] __cond_resched+0x1b/0x30 [
> > 0.055228] [<c1b292d5>] _cond_resched+0x45/0x50 [ 0.056020]
> > [<c1b26c58>] mutex_lock_nested+0x28/0x370 [ 0.056884]
> > [<c1034222>] ? console_unlock+0x3a2/0x4e0 [ 0.057741]
> > [<c1ac8559>] __irq_alloc_descs+0x39/0x1c0 [ 0.058589]
> > [<c10223bc>] io_apic_setup_irq_pin+0x2c/0x310 [ 0.060042]
> > [<c20638df>] setup_IO_APIC+0x101/0x744 [ 0.060878] [<c1021d51>] ?
> > clear_IO_APIC+0x31/0x50 [ 0.061695] [<c20600f4>]
> > native_smp_prepare_cpus+0x538/0x680 [ 0.062644] [<c2056a91>] ?
> > do_one_initcall+0x12c/0x12c [ 0.063517] [<c2056a91>] ?
> > do_one_initcall+0x12c/0x12c [ 0.064016] [<c2056adc>]
> > kernel_init+0x4b/0x17f [ 0.064790] [<c2056a91>] ?
> > do_one_initcall+0x12c/0x12c [ 0.065660] [<c1b2bbd6>]
> > kernel_thread_helper+0x6/0x10 [ 0.066592] IOAPIC[0]: Set routing
> > entry (2-1 -> 0x41 -> IRQ 1 Mode:0 Active:0 Dest:1) [ 0.068045]
> > IOAPIC[0]: Set routing entry (2-2 -> 0x51 -> IRQ 0 Mode:0 Active:0
> > Dest:1)
> >
> > Trace two (triggered by another config):
> >
> > [ 0.288018] tlb_flushall_shift is 0xffffffff [ 0.316019]
> > Freeing SMP alternatives: 20k freed [ 0.364022] BUG: scheduling
> > while atomic: swapper/0/1/0x10000002 [ 0.364022] no locks held by
> > swapper/0/1. [ 0.368023] Pid: 1, comm: swapper/0 Not tainted
> > 3.6.0-rc1 #1 [ 0.368023] Call Trace: [ 0.368023] [<79812e23>]
> > __schedule_bug+0x41/0x53 [ 0.372023] [<79820393>]
> > __schedule+0x62/0x488 [ 0.376023] [<792d17ae>] ?
> > radix_tree_lookup+0xa/0xc [ 0.376023] [<79071f4e>] ?
> > rcu_irq_exit+0x61/0x66 [ 0.376023] [<79026be7>] ?
> > irq_exit+0x60/0x6c [ 0.376023] [<790035df>] ? do_IRQ+0x6c/0x80 [
> > 0.380023] [<7903d794>] __cond_resched+0x16/0x26 [ 0.380023]
> > [<79820888>] _cond_resched+0x13/0x1c [ 0.380023] [<7909f30a>]
> > slab_pre_alloc_hook.isra.44+0x2e/0x33 [ 0.380023] [<790a09c6>]
> > kmem_cache_alloc+0x1b/0xbb [ 0.384024] [<792ce416>] ?
> > alloc_cpumask_var_node+0x1a/0x72 [ 0.384024] [<792ce416>]
> > alloc_cpumask_var_node+0x1a/0x72 [ 0.384024] [<792ce486>]
> > alloc_cpumask_var+0xb/0xd [ 0.388024] [<792ce493>]
> > zalloc_cpumask_var+0xb/0xd [ 0.388024] [<79bfe1fd>]
> > native_smp_prepare_cpus+0x93/0x380 [ 0.388024] [<79bf6a7e>] ?
> > do_one_initcall+0x10c/0x10c [ 0.388024] [<79bf6ac6>]
> > kernel_init+0x48/0x16e [ 0.392024] [<79bf6a7e>] ?
> > do_one_initcall+0x10c/0x10c [ 0.392024] [<7982241e>]
> > kernel_thread_helper+0x6/0xd [ 0.400025] smpboot: SMP disabled [
> > 0.400025] Performance Events:
> >
> > Thanks, Fengguang
> >


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