linux-kernel - Re: [PATCH -mm] oprofile: BUG: using smp_processor

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Message-ID: <48D7B60F.4000704@gmail.com>
Date:	Mon, 22 Sep 2008 17:13:19 +0200
From:	Andrea Righi <righi.andrea@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	robert.richter@....com, akpm@...ux-foundation.org,
	oprofile-list@...ts.sf.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm] oprofile: BUG: using smp_processor_id() in preemptible
 code

Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
>>> +	local_irq_save(flags);
>>>  	__get_cpu_var(switch_index) = 0;
>>> +	local_irq_restore(flags);
>> either use __raw_get_cpu_var() if we are for sure not preemptible 
>> here, or fix the preemption status of this codepath.
> 
> i've applied the patch below instead to tip/oprofile - agreed?
> 
> 	Ingo

Seems to work fine.

Thanks,
-Andrea

> 
> ------------>
> From 45f197ade73ba95681b9803680c75352fc0a1c0a Mon Sep 17 00:00:00 2001
> From: Andrea Righi <righi.andrea@...il.com>
> Date: Sat, 20 Sep 2008 12:58:40 +0200
> Subject: [PATCH] x86, oprofile: BUG: using smp_processor_id() in preemptible code
> 
> Add __raw access before setting per cpu variable switch_index, to avoid
> the following BUG:
> 
> [  449.166827] BUG: using smp_processor_id() in preemptible [00000000] code: modprobe/6998
> [  449.166848] caller is op_nmi_init+0xf0/0x2b0 [oprofile]
> [  449.166855] Pid: 6998, comm: modprobe Not tainted 2.6.27-rc5-mm1 #29
> [  449.166860] Call Trace:
> [  449.166872]  [<ffffffff80362d67>] debug_smp_processor_id+0xd7/0xe0
> [  449.166887]  [<ffffffffa00181c0>] op_nmi_init+0xf0/0x2b0 [oprofile]
> [  449.166902]  [<ffffffffa0018000>] oprofile_init+0x0/0x60 [oprofile]
> [  449.166915]  [<ffffffffa00180a9>] oprofile_arch_init+0x9/0x30 [oprofile]
> [  449.166928]  [<ffffffffa001801e>] oprofile_init+0x1e/0x60 [oprofile]
> [  449.166937]  [<ffffffff8020903b>] _stext+0x3b/0x160
> [  449.166946]  [<ffffffff80477985>] __mutex_unlock_slowpath+0xe5/0x190
> [  449.166955]  [<ffffffff80262c1a>] trace_hardirqs_on_caller+0xca/0x140
> [  449.166965]  [<ffffffff8026f7fc>] sys_init_module+0xdc/0x210
> [  449.166972]  [<ffffffff8020b7cb>] system_call_fastpath+0x16/0x1b
> 
> Signed-off-by: Andrea Righi <righi.andrea@...il.com>
> Acked-by: Robert Richter <robert.richter@....com>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  arch/x86/oprofile/nmi_int.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
> index fb4902b..4108d02 100644
> --- a/arch/x86/oprofile/nmi_int.c
> +++ b/arch/x86/oprofile/nmi_int.c
> @@ -551,7 +551,7 @@ int __init op_nmi_init(struct oprofile_operations *ops)
>  	}
>  
>  	/* default values, can be overwritten by model */
> -	__get_cpu_var(switch_index) = 0;
> +	__raw_get_cpu_var(switch_index) = 0;
>  	ops->create_files = nmi_create_files;
>  	ops->setup = nmi_setup;
>  	ops->shutdown = nmi_shutdown;
--
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