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| author | Mikulas Patocka <mpatocka@redhat.com> | 2018-05-30 08:19:22 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-06-04 17:28:20 -0400 |
| commit | 2026d35741f2c3ece73c11eb7e4a15d7c2df9ebe (patch) | |
| tree | f05eb8233131e271c1844dd17c8053e450d607b7 /include/linux/compiler.h | |
| parent | a9235b544a0ae95fbd56443bdbd251358c7df4c5 (diff) | |
| download | lwn-2026d35741f2c3ece73c11eb7e4a15d7c2df9ebe.tar.gz lwn-2026d35741f2c3ece73c11eb7e4a15d7c2df9ebe.zip | |
branch-check: fix long->int truncation when profiling branches
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>
Cc: stable@vger.kernel.org
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>
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ab4711c63601..42506e4d1f53 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -21,7 +21,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #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"))) \ |