Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] sbitmap: avoid maybe-uninitialized warning | Date | Mon, 19 Sep 2016 17:14:48 +0200 |
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On Monday, September 19, 2016 8:43:12 AM CEST Jens Axboe wrote: > On 09/19/2016 06:33 AM, Arnd Bergmann wrote: > > The sbitmap code that has just been turned into a library module > > returns uninitialized data for sbitmap_weight(), as pointed out by > > gcc when building with -Wmaybe-uninitialized: > > > > lib/sbitmap.c: In function 'sbitmap_weight': > > lib/sbitmap.c:179:9: error: 'weight' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > > > Note that the value is never initialized, we just add data on > > top, so it is wrong regardless of sb->map_nr. > > > > This adds the missing initialization. > > Thanks Arnd, Colin sent the same patch and I applied it. Note that:
Ok, thanks!
> > Fixes: 88459642cba4 ("blk-mq: abstract tag allocation out into sbitmap library") > > that isn't truly correct, that patch is just what moved the code. The > bug predates that commit.
It's not important as long as the bug is fixed now, but I think it was correct before that move, we just lost the 'used=0' initialization, which also triggered the warning:
-static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt) -{ - unsigned int i, used; - - for (i = 0, used = 0; i < bt->map_nr; i++) { - struct blk_align_bitmap *bm = &bt->map[i]; - - used += bitmap_weight(&bm->word, bm->depth); } - return bt->depth - used; }
Arnd
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