[lkml]   [2014]   [Oct]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: RCU bug with v3.17-rc3 ?
On 10/10/2014 11:25 AM, Russell King - ARM Linux wrote:
> Right, so GCC 4.8.{1,2} are totally unsuitable for kernel building (and
> it seems that this has been known about for some time.)

Looking at it seems that all 4.8.x for x < 3
are affected, as well as 4.9.0.

> We can blacklist these GCC versions quite easily. We already have GCC
> 3.3 blacklisted, and it's trivial to add others. I would want to include
> some proper details about the bug, just like the other existing entries
> we already have in asm-offsets.c, where we name the functions that the
> compiler is known to break where appropriate.

Before blacklisting anything, it's worth considering that simple version
checks would break existing pre-4.8.3 compilers that have been patched
for PR58854. It looks like Yocto and Buildroot issued releases with
patched 4.8.2 compilers well before the (fixed) 4.8.3 release. I think
the most we can reasonably do without breaking some correctly-behaving
toolchains is to emit a warning.

Hopefully nobody's still using gcc 4.8 from the Linaro 2013.11 toolchain
release -- since it's a 4.8.3 prerelease from before the fix was
committed you'll get GCC_VERSION == 40803 but still generate bad code.

> However, I'm rather annoyed that there are people here who have known
> for some time that GCC 4.8.1 and GCC 4.8.2 _can_ lead to filesystem
> corruption, and have sat on their backsides doing nothing about getting
> it blacklisted for something like a year.

Mea culpa, although I hadn't drawn the connection to FS corruption
reports until now. I have known about the issue for some time, but
figured the prevalence of the fix in downstream projects largely
mitigated the issue.

 \ /
  Last update: 2014-10-11 04:22    [W:0.103 / U:1.908 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site