[tip: sched/core] sched: Disable -Wunused-but-set-variable

["tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     37b47298ab864fb3f5488ddebfc35267ceab0553
Gitweb:        https://git.kernel.org/tip/37b47298ab864fb3f5488ddebfc35267ceab0553
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Tue, 12 Oct 2021 16:08:07 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 15 Oct 2021 11:25:15 +02:00

sched: Disable -Wunused-but-set-variable

The compilers can't deal with obvious DCE vs that warning, resulting
in code like:

	if (0) {
		sched sched_statistics *stats;

		stats = __schedstats_from_se(se);

		...
	}

triggering the warning. Kill the warning to make the robots stop
reporting this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YWWPLnaZGybHsTkv@hirez.programming.kicks-ass.net
---
 kernel/sched/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 978fcfc..c7421f2 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -3,6 +3,10 @@ ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_clock.o = $(CC_FLAGS_FTRACE)
 endif
 
+# The compilers are complaining about unused variables inside an if(0) scope
+# block. This is daft, shut them up.
+ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
+
 # These files are disabled because they produce non-interesting flaky coverage
 # that is not a function of syscall inputs. E.g. involuntary context switches.
 KCOV_INSTRUMENT := n