From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mikulas Patocka Subject: [PATCH 3/4] branch-check: fix long->int truncation when profiling branches Date: Wed, 30 May 2018 15:16:57 +0200 Message-ID: <20180530131822.086075870@debian.vm> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline; filename=branch_check-long.patch List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Mikulas Patocka , Mike Snitzer , Dan Williams Cc: dm-devel@redhat.com, stable@vger.kernel.org List-Id: dm-devel.ids 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 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"))) \