linux-kernel - Re: [PATCH] x86: mcheck: call put_device on device

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Date:	Sat, 30 Nov 2013 13:37:35 +0100
From:	Levente Kurusa <levex@...ux.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	EDAC <linux-edac@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: mcheck: call put_device on device_register failure

2013-11-30 13:08 keltezéssel, Borislav Petkov írta:
> On Sat, Nov 30, 2013 at 12:44:59PM +0100, Levente Kurusa wrote:
>> Yes, I saw that as well. By that I meant that by doing some identifier
>> searches for device_register and then checking whether they call
>> put_device and have device_release registered. Also, I wonder if it
>> would be beneficial to have a generic device_release? Most of the
>> drivers I quickly swept through only call kfree(). Wouldn't a generic
>> one save some space?
> 
> Again, I wouldn't waste my time with hypothetical issues which never
> happen - there are many other, real issues which would rather need
> attention than what-if ones.
> 
> About saving space, that could be worth a try. If you can actually do
> that and show numbers to back it up, I'm sure people will have a look.
> And if you can't show any space savings, you'll still have learned stuff
> along the way.
> 
> But don't ask me about whether it makes sense to have a generic
> device_release - I'm no driver core and am not even trying. You could
> try to answer that question yourself, btw. :)

Okay, I will, thanks for the tips! :)
> 
>> Yes, I do that daily usually, but most of the time I only get some
>> uninitialized warnings. :-)
> 
> You can always try to understand why such warnings get issued and maybe
> even fix them if they're legit and the compiler is right. Also, look
> through git log for examples how others have fixed such warnings.
Yes, but there are some fake one where for example it doesn't recognize the
pci_read_config_byte call as something which could write to its args. So most
of them are fake warnings.

> 
> For example, sometimes changing code flow instead of simply shutting
> up the variable is much better. But in order to do that, you'd need to
> understand the code first and try to change it so that it doesn't break
> and the warning disappears. This is a very good way, IMO, to get to
> really understand what the code does and learn from others.
> 
> Another good exercise is trying to boot those random kernels with kvm -
> that can catch a bunch of issues too.
> 
> The save-space experiment you can also quickly test with kvm. By now you
> probably are catching my drift: testing kernels with kvm is awesome! :-)
I will try kvm, didn't use that before. :p

> 
>> What does that do? Never heard of it yet.
> 
> Well, you can have a look: scripts/Makefile.build

Ahh, now I see. Just didn't know where to look.

> 
> :-)
> 
> Good luck!
Thank you and for your time! :)

-- 
Regards,
Levente Kurusa
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