[Buildroot] [PATCH] config: bump linux kernel to 4.8.6 in synopsys defconfigs

[Alexey Brodkin]

Hi Thomas,

On Mon, 2016-11-14 at 15:07 +0100, Thomas Petazzoni wrote:
> Hello,
> 
> On Mon, 14 Nov 2016 12:32:29 +0000, Vlad Zakharov wrote:
> 
> > 
> > We apologize for coming late with that update.
> > But could you please apply it on master as it is important for us to come up with latest kernel in upcoming
> > Buildroot release.
> > Updated configs were build- and run tested on corresponding platforms, so there shouldn't be any regressions there.
> 
> Once -rc1 has passed, we don't apply version bumps (be it to packages
> or defconfigs), unless they fix a specific issue.
> 
> What is the issue with having this update part of 2017.02 ?

Obviously since we live in upstream everything that could not be applied to
stable branches (i.e. is not a trivial fix and longer than 200 lines) get
merged in newer kernels.

In particular following commit was not accepted in
backports:

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=840c054fd0efb048df6fceb0c46385ec5b66dfe6

See discussion here http://www.spinics.net/lists/stable/msg143544.html

The problem is in GCC v6.x newer ABI is used for ARCv2 and so only kernels v4.8+
will work. I.e. existing 4.7 will fail to run user-space apps built with GCC 6.x.

Indeed we may add mentioned off-the-tree patch in BR for 4.7 but I'd rather bump
kernel version here with which we get more fixes across the tree for our users.

-Alexey