linux-kernel - [tip: sched/core] sched: Fix DEBUG && !SCHEDSTATS warn

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Date:   Wed, 06 Oct 2021 08:34:10 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Fix DEBUG && !SCHEDSTATS warn

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

Commit-ID:     769fdf83df57b373660343ef4270b3ada91ef434
Gitweb:        https://git.kernel.org/tip/769fdf83df57b373660343ef4270b3ada91ef434
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Wed, 06 Oct 2021 10:12:05 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 06 Oct 2021 10:30:57 +02:00

sched: Fix DEBUG && !SCHEDSTATS warn

When !SCHEDSTATS schedstat_enabled() is an unconditional 0 and the
whole block doesn't exist, however GCC figures the scoped variable
'stats' is unused and complains about it.

Upgrade the warning from -Wunused-variable to -Wunused-but-set-variable
by writing it in two statements. This fixes the build because the new
warning is in W=1.

Given that whole if(0) {} thing, I don't feel motivated to change
things overly much and quite strongly feel this is the compiler being
daft.

Fixes: cb3e971c435d ("sched: Make struct sched_statistics independent of fair sched class")
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/sched/debug.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 26fac5e..7dcbaa3 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -463,7 +463,8 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
 	PN(se->sum_exec_runtime);
 
 	if (schedstat_enabled()) {
-               struct sched_statistics *stats =  __schedstats_from_se(se);
+		struct sched_statistics *stats;
+		stats = __schedstats_from_se(se);
 
 		PN_SCHEDSTAT(wait_start);
 		PN_SCHEDSTAT(sleep_start);