On Wed, 30 May 2018 08:19:22 -0400 (EDT)
Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> 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
Nice catch.
> 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
I'm curious to what that bug was.
> better to fix __branch_check__ to return long.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Anyway, I can pull this in my tree and test it.
-- Steve
>
> ---
> 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"))) \
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
