linux-kernel - Re: [PATCH] kernel/watchdog.c : fix smp_processor

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Message-ID: <20120726194324.GG5637@redhat.com>
Date:	Thu, 26 Jul 2012 15:43:24 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Sameer Nanda <snanda@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/watchdog.c : fix smp_processor_id() warning

On Wed, Jul 25, 2012 at 12:39:45PM +0800, Ming Lei wrote:
> Use raw_smp_processor_id in lockup_detector_bootcpu_resume()
> because it is enough when non-boot CPUs are offline.
> 
> This patch fixes the following warning when DEBUG_PREEMPT
> is enabled.

Is this patched on top of linux-next?

It seems right based on the code usage.  Though it makes me sad the resume
code has to hack into the cpu notifiers like that.

Cheers,
Don

> 
> [  168.259429] BUG: using smp_processor_id() in preemptible [00000000] code: pm/1577
> [  168.259460] caller is lockup_detector_bootcpu_resume+0x8/0x48
> [  168.259490] [<c001558c>] (unwind_backtrace+0x0/0x11c) from [<c0296874>] (debug_smp_processor_id+0xbc/0xf0)
> [  168.259521] [<c0296874>] (debug_smp_processor_id+0xbc/0xf0) from [<c0090114>] (lockup_detector_bootcpu_res
> ume+0x8/0x48)
> [  168.259552] [<c0090114>] (lockup_detector_bootcpu_resume+0x8/0x48) from [<c006facc>] (suspend_devices_and_
> enter+0x1f8/0x358)
> [  168.259552] [<c006facc>] (suspend_devices_and_enter+0x1f8/0x358) from [<c006fd68>] (pm_suspend+0x13c/0x204
> )
> [  168.259582] [<c006fd68>] (pm_suspend+0x13c/0x204) from [<c006f0d0>] (state_store+0xb0/0xd4)
> [  168.259582] [<c006f0d0>] (state_store+0xb0/0xd4) from [<c028a3d8>] (kobj_attr_store+0x14/0x20)
> [  168.259613] [<c028a3d8>] (kobj_attr_store+0x14/0x20) from [<c014d344>] (sysfs_write_file+0x10c/0x140)
> [  168.259643] [<c014d344>] (sysfs_write_file+0x10c/0x140) from [<c00f5a88>] (vfs_write+0xb0/0x138)
> [  168.259643] [<c00f5a88>] (vfs_write+0xb0/0x138) from [<c00f5ce8>] (sys_write+0x3c/0x68)
> [  168.259674] [<c00f5ce8>] (sys_write+0x3c/0x68) from [<c000e020>] (ret_fast_syscall+0x0/0x48)
> [  168.260375] Enabling non-boot CPUs ...
> 
> Signed-off-by: Ming Lei <ming.lei@...onical.com>
> ---
>  kernel/watchdog.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 69add8a..7ddb11b 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -623,7 +623,7 @@ static struct notifier_block cpu_nfb = {
>   */
>  void lockup_detector_bootcpu_resume(void)
>  {
> -	void *cpu = (void *)(long)smp_processor_id();
> +	void *cpu = (void *)(long)raw_smp_processor_id();
>  
>  	cpu_callback(&cpu_nfb, CPU_DEAD_FROZEN, cpu);
>  	cpu_callback(&cpu_nfb, CPU_UP_PREPARE_FROZEN, cpu);
> -- 
> 1.7.9.5
> 
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