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

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Message-ID: <20120302122405.050ab634@jbarnes-desktop>
Date:	Fri, 2 Mar 2012 12:24:05 -0800
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Myron Stowe <myron.stowe@...hat.com>, 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, 2 Mar 2012 12:00:27 -0800
Greg KH <gregkh@...uxfoundation.org> wrote:

> 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?

It's just a self-documenting assert; doesn't trigger anything and has
more functionality than
  /* Must hold the fwaddrmap_lock here */


-- 
Jesse Barnes, Intel Open Source Technology Center

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