linux-kernel - Re: [PATCH] proc: use BUG_ON() in de

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Message-ID: <20071122084923.GA6240@localhost.sw.ru>
Date:	Thu, 22 Nov 2007 11:49:23 +0300
From:	Alexey Dobriyan <adobriyan@...ru>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, devel@...nvz.org
Subject: Re: [PATCH] proc: use BUG_ON() in de_put()

On Fri, Nov 16, 2007 at 01:46:42PM -0800, Andrew Morton wrote:
> On Thu, 15 Nov 2007 19:12:49 +0300
> Alexey Dobriyan <adobriyan@...ru> wrote:
> 
> > It's much more visible that some printk. I still has an unexplained oops
> > in proc, so let's leave it for a while.

> > --- a/fs/proc/inode.c
> > +++ b/fs/proc/inode.c
> > @@ -37,12 +37,7 @@ void de_put(struct proc_dir_entry *de)
> >  {
> >  	if (de) {	
> >  		lock_kernel();		
> > -		if (!atomic_read(&de->count)) {
> > -			printk("de_put: entry %s already free!\n", de->name);
> > -			unlock_kernel();
> > -			return;
> > -		}
> > -
> > +		BUG_ON(atomic_read(&de->count) == 0);
> >  		if (atomic_dec_and_test(&de->count)) {
> >  			if (de->deleted) {
> >  				printk("de_put: deferred delete of %s\n",
> 
> I don't see that an error in here _requires_ that we nuke the machine. 
> Surely we can emit a warning and then recover in some fashion?

Hmm... atomic_dec_and_test() in -mm already has diagnostics¹ when doing
0 => -1 transition, google says this check triggered only once. I think
we should just drop it.

¹ i386 only :^)

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