linux-kernel - Re: [PATCHv3 1/1] sysfs: add more info to the oops dump

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Date:	Thu, 10 Mar 2011 23:59:26 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Phil Carmody <ext-phil.2.carmody@...ia.com>, gregkh@...e.de,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 1/1] sysfs: add more info to the oops dump

On Thu, 10 Mar 2011, Andrew Morton wrote:

> On Fri, 11 Mar 2011 00:27:07 +0200
> Phil Carmody <ext-phil.2.carmody@...ia.com> wrote:
> 
> > +static int last_sysfs_write_len;
> >  void sysfs_printk_last_file(void)
> >  {
> > -	printk(KERN_EMERG "last sysfs file: %s\n", last_sysfs_file);
> > +	printk(KERN_EMERG "last sysfs file (%c): %s%c",
> > +	       (last_sysfs_write_len == SYSFS_NOT_A_WRITE) ? 'r' : 'w',
> > +	       last_sysfs_file,
> > +	       last_sysfs_write_len > 0 ? ' ' : '\n');
> > +	if (last_sysfs_write_len >= (int)sizeof(last_sysfs_write))
> > +		printk(KERN_CONT " written: %s...(%d chars)\n",
> > +		       last_sysfs_write, last_sysfs_write_len);
> > +	else if (last_sysfs_write_len > 0)
> > +		printk(KERN_CONT " written: %s\n", last_sysfs_write);
> >  }
> 
> That's going to fail to emit the \n if last_sysfs_write_len<=0. 
> However there are tricks inside printk() which will fix that up if the
> next printk starts with KERN_foo.
> 
> 
> 
> I can recall just one instance in the past 5-6 years in which the
> last-sysfs-file output enabled me to locate a bug which would otherwise
> have been unlocatable (within a drivers/md handler, iirc).
> 
> I don't think it's a terribly useful feature.  Except for when it _is_
> useful, when it's very useful ;) The world wouldn't end if we decided
> to remove it.

Amen to that.

It's more of an distraction than anything which is relevant to 99.999%
of the problems we have to deal with.

Thanks,

	tglx
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