sched: register the schedulers into the list

Adds a simple macro to place a pointer to a scheduler into an array
section at compile time. Also, goes ahead and generates the array
entries with each of the schedulers.

Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Acked-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/common/sched_arinc653.c

@@ -767,6 +767,8 @@ const struct scheduler sched_arinc653_def = {
     .tick_resume    = NULL,
 };
 
+REGISTER_SCHEDULER(sched_arinc653_def);
+
 /*
  * Local variables:
  * mode: C

xen/common/sched_credit.c

@@ -2027,3 +2027,5 @@ const struct scheduler sched_credit_def = {
     .tick_suspend   = csched_tick_suspend,
     .tick_resume    = csched_tick_resume,
 };
+
+REGISTER_SCHEDULER(sched_credit_def);

xen/common/sched_credit2.c

@@ -2228,3 +2228,5 @@ const struct scheduler sched_credit2_def = {
     .alloc_domdata  = csched2_alloc_domdata,
     .free_domdata   = csched2_free_domdata,
 };
+
+REGISTER_SCHEDULER(sched_credit2_def);

xen/common/sched_rt.c

@@ -1199,3 +1199,5 @@ const struct scheduler sched_rtds_def = {
     .wake           = rt_vcpu_wake,
     .context_saved  = rt_context_saved,
 };
+
+REGISTER_SCHEDULER(sched_rtds_def);

xen/include/xen/sched-if.h

@@ -170,6 +170,8 @@ extern const struct scheduler sched_credit2_def;
 extern const struct scheduler sched_arinc653_def;
 extern const struct scheduler sched_rtds_def;
 
+#define REGISTER_SCHEDULER(x) static const struct scheduler *x##_entry \
+  __used_section(".data.schedulers") = &x;
 
 struct cpupool
 {