Messages in this thread Patch in this message | | | Date | Fri, 27 Apr 2007 17:22:30 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/memory.c: remove warning from an uninitialized spinlock. was: Re: 2.6.21-rc7-mm2 |
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On Thu, 26 Apr 2007 20:25:19 +0200 Borislav Petkov <bbpetkov@yahoo.de> wrote:
> > Remove build warning mm/memory.c:1491: warning: 'ptl' may be used uninitialized in this function. > The spinlock pointer is assigned to null since it gets overwritten right away in > pte_alloc_map_lock(). > > Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de> > --- > > Index: linux-mm/mm/memory.c > =================================================================== > --- linux-mm.orig/mm/memory.c 2007-04-26 19:57:14.000000000 +0200 > +++ linux-mm/mm/memory.c 2007-04-26 20:00:30.000000000 +0200 > @@ -1488,7 +1488,7 @@ > pte_t *pte; > int err; > struct page *pmd_page; > - spinlock_t *ptl; > + spinlock_t *ptl = NULL; > > pte = (mm == &init_mm) ? > pte_alloc_kernel(pmd, addr) : >
yes, I've been staring unhappily at this for some time.
Your change adds seven bytes of text to this function for no runtime benefit, just to fix a build-time warning. It's a general problem.
Often we just leave the warning in place and curse gcc each time it flies past. Sometimes the code can be restructured in a sensible fashion to avoid the warning; often it cannot.
But I don't think I want to put up with a warning coming out of core MM all the time so let's go with the following silliness which adds no additional runtime cost.
--- a/mm/memory.c~add-apply_to_page_range-which-applies-a-function-to-a-pte-range-fix +++ a/mm/memory.c @@ -1455,7 +1455,7 @@ static int apply_to_pte_range(struct mm_ pte_t *pte; int err; struct page *pmd_page; - spinlock_t *ptl; + spinlock_t *ptl = ptl; /* Suppress gcc warning */ pte = (mm == &init_mm) ? pte_alloc_kernel(pmd, addr) : _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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