linux-kernel - Re: [PATCH] x86 MCE: shut up lockdep warning

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Message-ID: <4A03EA8C.9040104@jp.fujitsu.com>
Date:	Fri, 08 May 2009 17:17:16 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Shaohua Li <shaohua.li@...el.com>
CC:	lkml <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86 MCE: shut up lockdep warning

Shaohua Li wrote:
> lockdep report below warning when I try to offline one cpu:
> [  110.835487] =================================
> [  110.835616] [ INFO: inconsistent lock state ]
> [  110.835688] 2.6.30-rc4-00336-g8c9ed89 #52
> [  110.835757] ---------------------------------
> [  110.835828] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
> [  110.835908] swapper/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
> [  110.835982]  (cmci_discover_lock){?.+...}, at: [<ffffffff80236dc0>] cmci_clear+0x30/0x9b
> 
> smp_call_function_single() will disable interrupt. moving mce reenable/disable
> to workqueue, so no irq is disabled.

I want a confirmation.
Will this scheduled work be executed properly on the cpu which is going
to offline?

> @@ -1106,14 +1108,14 @@ static int __cpuinit mce_cpu_callback(struct notifier_block *nfb,
>  	case CPU_DOWN_PREPARE:
>  	case CPU_DOWN_PREPARE_FROZEN:
>  		del_timer_sync(t);
> -		smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
> +		work_on_cpu(cpu, mce_disable_cpu, &action);
>  		break;
>  	case CPU_DOWN_FAILED:
>  	case CPU_DOWN_FAILED_FROZEN:
>  		t->expires = round_jiffies(jiffies +
>  						__get_cpu_var(next_interval));
>  		add_timer_on(t, cpu);
> -		smp_call_function_single(cpu, mce_reenable_cpu, &action, 1);
> +		work_on_cpu(cpu, mce_reenable_cpu, &action);
>  		break;
>  	case CPU_POST_DEAD:
>  		/* intentionally ignoring frozen here */
> 

I believe there is strong reason to have "1" in the last argument of
smp_call_function_single().


Thanks,
H.Seto

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