Re: [PATCH 5/9] pwm: spear: Remove unnecessary OOM messages

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Dan,

On Monday 03 March 2014 12:53:11 Dan Carpenter wrote:
> On Mon, Mar 03, 2014 at 10:14:22AM +0900, Jingoo Han wrote:
> > On Wednesday, February 26, 2014 3:26 PM, Viresh Kumar wrote:
> > > On 26 February 2014 10:49, Joe Perches <joe@perches.com> wrote:
> > > > Look at warn_alloc_failed() in mm/page_alloc.c
> > > 
> > > Okay, there is a print there. But I am not able to reach to this routine
> > > from devm_kzalloc().
> > > 
> > > devm_kzalloc() <linux/device.h>
> > > devm_kmalloc() <drivers/base/devres.c>
> > > alloc_dr() <drivers/base/devres.c>
> > > kmalloc_track_caller() <linux/slab.h>
> > > __kmalloc_track_caller() <mm/slab,slub/slob.c> Taking slab as example:
> > > __do_kmalloc() <mm/slab.c>
> > 
> > (+CC Laurent Pinchart, Dan Carpenter)
> > 
> > Right, I also cannot find that warn_alloc_failed() is called, during
> > devm_kzalloc().
> > 
> > However, in the case of vmalloc(), warn_alloc_failed() is called
> > as below.
> > 
> > ./mm/vmalloc.c
> > vmalloc()
> > __vmalloc_node_flags()
> > __vmalloc_node()
> > __vmalloc_node_range()
> > 
> > ./mm/page_alloc.c
> > warn_alloc_failed()
> > 
> > > ...
> > > 
> > > I can see cases where NULL is returned after above paths and the
> > > function you mentioned wasn't there. So, I am not sure that we will get
> > > a print for sure for any error that might occur from devm_kzalloc().
> > 
> > I guess that slab_out_of_memory() <./mm/slub.c> may print it for any
> > errors. But, I am not sure. :-(
> 
> devm_kzalloc() is just kmalloc().  The OOM error messages are the same.

Sure, but I wasn't sure whether all error code paths in kmalloc() resulted in 
an OOM message. For instance, the following code path results in an allocation 
failure but doesn't seem to print an OOM message:

kmalloc
__kmalloc
__do_kmalloc
slab_alloc
slab_should_failslab
should_failslab
should_fail

A bit far-fetched possibly as it requires fault injection. I haven't found any 
other such code path, but my understanding of that code is a bit limited.

-- 
Regards,

Laurent Pinchart