linux-kernel - Re: [PATCH] x86/PCI: add spinlock held check to 'pcibios_fwaddrmap

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Date:	Fri, 2 Mar 2012 12:00:27 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Myron Stowe <myron.stowe@...hat.com>
Cc:	jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/PCI: add spinlock held check to
 'pcibios_fwaddrmap_lookup()'

On Fri, Mar 02, 2012 at 12:45:01PM -0700, Myron Stowe wrote:
> 'pcibios_fwaddrmap_lookup()' is used to maintain FW-assigned BIOS BAR
> values for reinstatement when normal resource assignment attempts
> fail and must be called with the 'pcibios_fwaddrmap_lock' spinlock
> held.
> 
> This patch adds a WARN_ON notification if the spinlock is not currently
> held by the caller.
> 
> Signed-off-by: Myron Stowe <myron.stowe@...hat.com>
> ---
> 
>  arch/x86/pci/i386.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
> index 33e6a0b..831971e 100644
> --- a/arch/x86/pci/i386.c
> +++ b/arch/x86/pci/i386.c
> @@ -57,6 +57,8 @@ static struct pcibios_fwaddrmap *pcibios_fwaddrmap_lookup(struct pci_dev *dev)
>  {
>  	struct pcibios_fwaddrmap *map;
>  
> +	WARN_ON(!spin_is_locked(&pcibios_fwaddrmap_lock));
> +

What is this going to help with?  How can someone then recover from this
issue?  Just adding a warning message isn't going to fix any problems
here, why not fix the root cause?

thanks,

greg k-h
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