On Mon 24-10-16 21:42:36, Arnd Bergmann wrote:
> On Monday, October 24, 2016 6:22:44 PM CEST Michal Hocko wrote:
> > On Mon 24-10-16 17:25:03, Arnd Bergmann wrote:
> > > After enabling -Wmaybe-uninitialized warnings, we get a false-postive
> > > warning for shmem:
> > >
> > > mm/shmem.c: In function ‘shmem_getpage_gfp’:
> > > include/linux/spinlock.h:332:21: error: ‘info’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> >
> > Is this really a false positive? If we goto clear and then
> > if (sgp <= SGP_CACHE &&
> > ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
> > if (alloced) {
> >
> > we could really take a spinlock on an unitialized variable. But maybe
> > there is something that prevents from that...
>
> I did the patch a few weeks ago (I sent the more important
> ones out first) and I think I concluded then that 'alloced'
> would be false in that case.
OK, I guess you are right and alloced is set only after info has been
already initialized. So this really looks like a false positive.
>
> > Anyway the whole shmem_getpage_gfp is really hard to follow due to gotos
> > and labels proliferation.
>
> Exactly. Maybe we should mark the patch for -stable backports after all
> just to be sure.
I am not really sure a stable backport is really necessary but a cleanup
in this area would be more than welcome. At least from me ;)
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>