[PATCH 5/9] tools/sched_ext: scx_pair: Reset pair_id on restart

[Tao Cui <cui.tao@linux.dev>]

From: Tao Cui <cuitao@kylinos.cn>

pair_id is initialized to 0 before the restart: label, so a reload
triggered by an ops restart (e.g. a hotplug event with the scheduler
providing no cpu_online/cpu_offline callbacks) jumps back to the label
with pair_id still holding the previous run's counter. Since f546c77038ab
("tools/sched_ext: scx_pair: fix pair_ctx indexing for CPU pairs")
pair_id is a dense index into the pair_ctx array, so the second load
starts pairing CPUs past the end of the array and the scheduler can
never come up again.

Initialize pair_id after the label so every reload starts from a clean
counter.

Fixes: f546c77038ab ("tools/sched_ext: scx_pair: fix pair_ctx indexing for CPU pairs")
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
 tools/sched_ext/scx_pair.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/sched_ext/scx_pair.c b/tools/sched_ext/scx_pair.c
index 35c8a1a07f56..f15093e002f0 100644
--- a/tools/sched_ext/scx_pair.c
+++ b/tools/sched_ext/scx_pair.c
@@ -48,12 +48,13 @@ int main(int argc, char **argv)
 	struct bpf_link *link;
 	__u64 seq = 0, ecode;
 	__s32 stride, i, opt, outer_fd;
-	__u32 pair_id = 0;
+	__u32 pair_id;
 
 	libbpf_set_print(libbpf_print_fn);
 	signal(SIGINT, sigint_handler);
 	signal(SIGTERM, sigint_handler);
 restart:
+	pair_id = 0;
 	optind = 1;
 	skel = SCX_OPS_OPEN(pair_ops, scx_pair);
 
-- 
2.53.0

base-commit: 5b740a72b55c4267ba4d8010f17dde26b26f52d3