The slub allocator gives us some incorrect warnings when CONFIG_PROFILE_ANNOTATED_BRANCHES is set, as the unlikely() macro prevents it from seeing that the return code matches what it was before:
mm/slub.c: In function ‘kmem_cache_free_bulk’: mm/slub.c:262:23: error: ‘df.s’ may be used uninitialized in this function [-Werror=maybe-uninitialized] mm/slub.c:2943:3: error: ‘df.cnt’ may be used uninitialized in this function [-Werror=maybe-uninitialized] mm/slub.c:2933:4470: error: ‘df.freelist’ may be used uninitialized in this function [-Werror=maybe-uninitialized] mm/slub.c:2943:3: error: ‘df.tail’ may be used uninitialized in this function [-Werror=maybe-uninitialized] I have not been able to come up with a perfect way for dealing with this, the three options I see are: - add a bogus initialization, which would increase the runtime overhead - replace unlikely() with unlikely_notrace() - remove the unlikely() annotation completely I checked the object code for a typical x86 configuration and the last two cases produce the same result, so I went for the last one, which is the simplest. Signed-off-by: Arnd Bergmann <[email protected]> --- mm/slub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index 2b3e740609e9..68b84f93d38d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3076,7 +3076,7 @@ void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p) struct detached_freelist df; size = build_detached_freelist(s, size, p, &df); - if (unlikely(!df.page)) + if (!df.page) continue; slab_free(df.s, df.page, df.freelist, df.tail, df.cnt,_RET_IP_); -- 2.9.0
