Sync with scx repo

tools/sched_ext/include/scx/common.bpf.h

@@ -276,6 +276,8 @@ static inline u32 bpf_log2l(u64 v)
 /* useful compiler attributes */
 #define likely(x) __builtin_expect(!!(x), 1)
 #define unlikely(x) __builtin_expect(!!(x), 0)
+#define __maybe_unused __attribute__((__unused__))
+
 
 void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
 void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;

tools/sched_ext/scx_central.bpf.c

@@ -305,6 +305,7 @@ int BPF_STRUCT_OPS_SLEEPABLE(central_init)
 	struct bpf_timer *timer;
 	int ret;
 
+	__COMPAT_scx_bpf_switch_all();
 	ret = scx_bpf_create_dsq(FALLBACK_DSQ_ID, -1);
 	if (ret)
 		return ret;

tools/sched_ext/scx_flatcg.bpf.c

@@ -16,7 +16,7 @@
  *
  * For example, B is competing against C and in that competition its share is
  * 100/(100+100) == 1/2. At its parent level, A is competing against D and A's
- * share in that competition is 200/(200+100) == 1/3. B's eventual share in the
+ * share in that competition is 100/(200+100) == 1/3. B's eventual share in the
  * system can be calculated by multiplying the two shares, 1/2 * 1/3 == 1/6. C's
  * eventual shaer is the same at 1/6. D is only competing at the top level and
  * its share is 200/(100+200) == 2/3.

tools/sched_ext/scx_simple.bpf.c

@@ -29,6 +29,13 @@ const volatile bool fifo_sched;
 static u64 vtime_now;
 UEI_DEFINE(uei);
 
+/*
+ * Built-in DSQs such as SCX_DSQ_GLOBAL cannot be used as priority queues
+ * (meaning, cannot be dispatched to with scx_bpf_dispatch_vtime()). We
+ * therefore create a separate DSQ with ID 0 that we dispatch to and consume
+ * from. If scx_simple only supported global FIFO scheduling, then we could
+ * just use SCX_DSQ_GLOBAL.
+ */
 #define SHARED_DSQ 0
 
 struct {
@@ -129,6 +136,7 @@ void BPF_STRUCT_OPS(simple_enable, struct task_struct *p)
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(simple_init)
 {
+	__COMPAT_scx_bpf_switch_all();
 	return scx_bpf_create_dsq(SHARED_DSQ, -1);
 }