[PATCH 11/12] sched_ext: scx_qmap - Idle-check pinned tasks before direct dispatch

[Tejun Heo <tj@kernel.org>]

pick_direct_dispatch_cid() sent a pinned task straight to its only cpu
without an idle check. An insert onto a time-shared cid is forced IMMED,
which may not wait on a busy cpu - the kernel bounces the task back to
ops.enqueue(), the shortcut re-inserts it, and the loop runs into the
reenqueue repeat limit.

Run pinned tasks through the same idle test as everyone else and queue them
when the cpu is busy. always_enq_immed forces IMMED on every local insert
and already skipped the shortcut for the same reason.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 tools/sched_ext/scx_qmap.bpf.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index 8822ed11c0d8..9a0321e84e88 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -230,9 +230,6 @@ static s32 pick_direct_dispatch_cid(struct task_struct *p, s32 prev_cid,
 	s32 cid;
 	u32 i;
 
-	if (!always_enq_immed && p->nr_cpus_allowed == 1)
-		return prev_cid;
-
 	if (cmask_test(prev_cid, &qa.self_cids.mask) &&
 	    cmask_test_and_clear(prev_cid, &qa.idle_cids.mask))
 		return prev_cid;
-- 
2.55.0