scx: Fix exit selftest to use custom DSQ

In commit 63fb3ec ("sched_ext: Allow only user DSQs for
scx_bpf_consume(), scx_bpf_dsq_nr_queued() and bpf_iter_scx_dsq_new()"), we
updated the consume path to only accept user DSQs, thus making it invalid
to consume SCX_DSQ_GLOBAL. This selftest was doing that, so let's create a
custom DSQ and use that instead.  The test now passes:

[root@virtme-ng sched_ext]# ./runner -t exit
===== START =====
TEST: exit
DESCRIPTION: Verify we can cleanly exit a scheduler in multiple places
OUTPUT:
[   12.387229] sched_ext: BPF scheduler "exit" enabled
[   12.406064] sched_ext: BPF scheduler "exit" disabled (unregistered from BPF)
[   12.453325] sched_ext: BPF scheduler "exit" enabled
[   12.474064] sched_ext: BPF scheduler "exit" disabled (unregistered from BPF)
[   12.515241] sched_ext: BPF scheduler "exit" enabled
[   12.532064] sched_ext: BPF scheduler "exit" disabled (unregistered from BPF)
[   12.592063] sched_ext: BPF scheduler "exit" disabled (unregistered from BPF)
[   12.654063] sched_ext: BPF scheduler "exit" disabled (unregistered from BPF)
[   12.715062] sched_ext: BPF scheduler "exit" disabled (unregistered from BPF)
ok 1 exit #
=====  END  =====

Signed-off-by: David Vernet <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

Author: Byte-Lab

tools/testing/selftests/sched_ext/exit.bpf.c

@@ -15,6 +15,8 @@ UEI_DEFINE(uei);
 
 #define EXIT_CLEANLY() scx_bpf_exit(exit_point, "%d", exit_point)
 
+#define DSQ_ID 0
+
 s32 BPF_STRUCT_OPS(exit_select_cpu, struct task_struct *p,
 		   s32 prev_cpu, u64 wake_flags)
 {
@@ -31,15 +33,15 @@ void BPF_STRUCT_OPS(exit_enqueue, struct task_struct *p, u64 enq_flags)
 	if (exit_point == EXIT_ENQUEUE)
 		EXIT_CLEANLY();
 
-	scx_bpf_dispatch(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, enq_flags);
+	scx_bpf_dispatch(p, DSQ_ID, SCX_SLICE_DFL, enq_flags);
 }
 
 void BPF_STRUCT_OPS(exit_dispatch, s32 cpu, struct task_struct *p)
 {
 	if (exit_point == EXIT_DISPATCH)
 		EXIT_CLEANLY();
 
-	scx_bpf_consume(SCX_DSQ_GLOBAL);
+	scx_bpf_consume(DSQ_ID);
 }
 
 void BPF_STRUCT_OPS(exit_enable, struct task_struct *p)
@@ -67,7 +69,7 @@ s32 BPF_STRUCT_OPS_SLEEPABLE(exit_init)
 	if (exit_point == EXIT_INIT)
 		EXIT_CLEANLY();
 
-	return 0;
+	return scx_bpf_create_dsq(DSQ_ID, -1);
 }
 
 SEC(".struct_ops.link")