Commit 2026d357 authored May 30, 2018 by Mikulas Patocka Committed by Steven Rostedt (VMware) Jun 04, 2018

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: 1f0d69a9 ("tracing: profile likely and unlikely annotations")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent a9235b54

include/linux/compiler.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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"))) \

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