| From: Mikulas Patocka <mpatocka@redhat.com> |
| Date: Wed, 30 May 2018 08:19:22 -0400 |
| Subject: branch-check: fix long->int truncation when profiling branches |
| |
| commit 2026d35741f2c3ece73c11eb7e4a15d7c2df9ebe upstream. |
| |
| 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. |
| |
| Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1805300818140.24812@file01.intranet.prod.int.rdu2.redhat.com |
| |
| Cc: Ingo Molnar <mingo@redhat.com> |
| Fixes: 1f0d69a9fc815 ("tracing: profile likely and unlikely annotations") |
| Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> |
| Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
| [bwh: Backported to 3.16: adjust context] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| include/linux/compiler.h | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/include/linux/compiler.h |
| +++ b/include/linux/compiler.h |
| @@ -105,7 +105,7 @@ void ftrace_likely_update(struct ftrace_ |
| #define unlikely_notrace(x) __builtin_expect(!!(x), 0) |
| |
| #define __branch_check__(x, expect) ({ \ |
| - int ______r; \ |
| + long ______r; \ |
| static struct ftrace_branch_data \ |
| __attribute__((__aligned__(4))) \ |
| __attribute__((section("_ftrace_annotated_branch"))) \ |
