On Fri, Dec 15, 2017 at 7:01 PM, Yang Shi <yan...@alibaba-inc.com> wrote: > > > On 12/15/17 4:51 AM, Arnd Bergmann wrote: >> >> When the down_read_trylock() fails, 'vma' has not been initialized >> yet, which gcc now warns about: >> >> mm/khugepaged.c: In function 'khugepaged': >> mm/khugepaged.c:1659:25: error: 'vma' may be used uninitialized in this >> function [-Werror=maybe-uninitialized] > > > Arnd, > > Thanks for catching this. I'm wondering why my test didn't catch it. It > might be because my gcc is old. I'm using gcc 4.8.5 on centos 7.
Correct, gcc-4.8 and earlier have too many false-positive warnings with -Wmaybe-uninitialized, so we turn it off on those versions. 4.9 is much better here, but I'd recommend using gcc-6 or gcc-7 when you upgrade, they have a much better set of default warnings besides producing better binary code. See http://git.infradead.org/users/segher/buildall.git for a simple way to build toolchains suitable for building kernels in varying architectures and versions. Arnd
