On Thu, May 01, 2008 at 02:25:33PM -0600, Matthew Wilcox wrote:
> On Thu, May 01, 2008 at 10:43:25PM +0300, Adrian Bunk wrote:
> > > > - struct vm_area_struct *vma, *prev;
> > > > + struct vm_area_struct *vma, *prev = NULL;
> > >
> > > gcc bug -- it's failing to notice that find_vma_prepare() will always
> > > initialise pprev.
> > >...
> >
> > You miss the "return" inside the while() loop in find_vma_prepare().
> >
> > I do not know whether the code is correct, but the answer is not that
> > easy.
>
> You're right, it isn't that easy.
>
> However, the code is not buggy. Just compare:
>
> vma = vma_tmp;
> if (vma_tmp->vm_start <= addr)
> return vma;
>
> with
>
> munmap_back:
> vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
> if (vma && vma->vm_start < addr + len) {
> if (do_munmap(mm, addr, len))
> return -ENOMEM;
> goto munmap_back;
> }
>
> Now, we know that addr + len does not wrap, and that len > 0, so we know
> that this warning is incorrect. But it's not reasonable to expect gcc to
> be able to deduce this.
>...
Can you submit a patch with your explanation that uses
uninitialized_var() to silence these warnings?
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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