Re: [PATCH 4.4 16/30] [media] pvrusb2: reduce stack usage pvr2_eeprom_analyze()
From: Ben Hutchings
Date: Mon Jul 03 2017 - 11:07:40 EST
On Mon, 2017-07-03 at 09:47 +0200, Arnd Bergmann wrote:
> On Mon, Jul 3, 2017 at 9:31 AM, Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Thu, Jun 29, 2017 at 05:15:17PM +0100, Ben Hutchings wrote:
> >> On Mon, 2017-06-19 at 23:20 +0800, Greg Kroah-Hartman wrote:
> >> > 4.4-stable review patch. If anyone has any objections, please let me know.
> >> >
> >> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >> >
> >> > commit 6830733d53a4517588e56227b9c8538633f0c496 upstream.
> >> > Further analysis shows that putting an 'i2c_client' structure on
> >> > the stack is not really supported, as the embedded 'struct device'
> >> > is not initialized here, and we are only saved by the fact that
> >> > the function that is called here does not use the pointer at all.
> >> [...]
> >> That is not true in 4.4-stable. This commit depends on:
> >> commit 6037b3ca28f4258d913dbe77248fd77827702ae3
> >> Author: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> >> Date: Wed Nov 16 14:21:48 2016 -0200
> >> [media] tveeprom: print log messages using pr_foo()
> > It does? I don't understand how the two are connected. Removing
> > i2c_client off of the stack is a good thing. Ah, I see how the pointer
> > is used in tveeprom_hauppauge_analog(), but this shouldn't matter here,
> > right?
> My reading of the two patches is that we actually need at least one
> of them to avoid interpreting uninitialized dev->class/bus: With just my
> 6830733d53a patch, we replace the uninitialized data with a NULL
> pointer, which is handled gracefully in __dev_printk(), while the
> 6037b3ca28 patch by itself will avoid using the 'dev' pointer completely,
> and give a saner output (no "(NULL device)" string or worse).
> I think we probably want both of them backported to 4.4, but I don't see a
> dependency between them.
Sorry, I mixed up two commits. The one actually needed to avoid a null
Author: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
Date: Thu Oct 13 10:51:20 2016 -0300
[media] tveeprom: use dev_foo() for printk messages
Then "[media] tveeprom: print log messages using pr_foo()" is cleanup on
top of that.
Software Developer, Codethink Ltd.