The function __builtin_expect returns long type (see the gcc documentation), and so do macros likely and unlikely. Unfortunatelly, when CONFIG_PROFILE_ANNOTATED_BRANCHES is selected, the macros likely and unlikely expand to __branch_check__ and __branch_check__ truncates the long type to int. This unintended truncation may cause bugs in various kernel code (we found a bug in dm-writecache because of it), so it's better to fix __branch_check__ to return long.
Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org
--- include/linux/compiler.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux-2.6/include/linux/compiler.h =================================================================== --- linux-2.6.orig/include/linux/compiler.h 2018-02-26 20:34:17.000000000 +0100 +++ linux-2.6/include/linux/compiler.h 2018-05-30 14:11:53.000000000 +0200 @@ -21,7 +21,7 @@ void ftrace_likely_update(struct ftrace_ #define unlikely_notrace(x) __builtin_expect(!!(x), 0)
#define __branch_check__(x, expect, is_constant) ({ \ - int ______r; \ + long ______r; \ static struct ftrace_likely_data \ __attribute__((__aligned__(4))) \ __attribute__((section("_ftrace_annotated_branch"))) \