[PATCH v3 3/6] xen/sched: retrieve scheduler id by name

[Luca Fancellu <luca.fancellu@xxxxxxx>]

Add a static function to retrieve the scheduler pointer using the
scheduler name.

Add a public function to retrieve the scheduler id by the scheduler
name that makes use of the new static function.

Take the occasion to replace open coded scheduler search with the
new static function in scheduler_init.

Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
---
Changes in v3:
- add R-by
Changes in v2:
- replace open coded scheduler search in scheduler_init (Juergen)
---
 xen/common/sched/core.c | 40 ++++++++++++++++++++++++++--------------
 xen/include/xen/sched.h | 11 +++++++++++
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 19ab67818106..48ee01420fb8 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -2947,10 +2947,30 @@ void scheduler_enable(void)
     scheduler_active = true;
 }
 
+static inline
+const struct scheduler *__init sched_get_by_name(const char *sched_name)
+{
+    unsigned int i;
+
+    for ( i = 0; i < NUM_SCHEDULERS; i++ )
+        if ( schedulers[i] && !strcmp(schedulers[i]->opt_name, sched_name) )
+            return schedulers[i];
+
+    return NULL;
+}
+
+int __init sched_get_id_by_name(const char *sched_name)
+{
+    const struct scheduler *scheduler = sched_get_by_name(sched_name);
+
+    return scheduler ? scheduler->sched_id : -1;
+}
+
 /* Initialise the data structures. */
 void __init scheduler_init(void)
 {
     struct domain *idle_domain;
+    const struct scheduler *scheduler;
     int i;
 
     scheduler_enable();
@@ -2981,25 +3001,17 @@ void __init scheduler_init(void)
                    schedulers[i]->opt_name);
             schedulers[i] = NULL;
         }
-
-        if ( schedulers[i] && !ops.name &&
-             !strcmp(schedulers[i]->opt_name, opt_sched) )
-            ops = *schedulers[i];
     }
 
-    if ( !ops.name )
+    scheduler = sched_get_by_name(opt_sched);
+    if ( !scheduler )
     {
         printk("Could not find scheduler: %s\n", opt_sched);
-        for ( i = 0; i < NUM_SCHEDULERS; i++ )
-            if ( schedulers[i] &&
-                 !strcmp(schedulers[i]->opt_name, CONFIG_SCHED_DEFAULT) )
-            {
-                ops = *schedulers[i];
-                break;
-            }
-        BUG_ON(!ops.name);
-        printk("Using '%s' (%s)\n", ops.name, ops.opt_name);
+        scheduler = sched_get_by_name(CONFIG_SCHED_DEFAULT);
+        BUG_ON(!scheduler);
+        printk("Using '%s' (%s)\n", scheduler->name, scheduler->opt_name);
     }
+    ops = *scheduler;
 
     if ( cpu_schedule_up(0) )
         BUG();
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 415b939ba8ae..4050e22544f9 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -756,6 +756,17 @@ void sched_destroy_domain(struct domain *d);
 long sched_adjust(struct domain *, struct xen_domctl_scheduler_op *);
 long sched_adjust_global(struct xen_sysctl_scheduler_op *);
 int  sched_id(void);
+
+/*
+ * sched_get_id_by_name - retrieves a scheduler id given a scheduler name
+ * @sched_name: scheduler name as a string
+ *
+ * returns:
+ *     positive value being the scheduler id, on success
+ *     negative value if the scheduler name is not found.
+ */
+int sched_get_id_by_name(const char *sched_name);
+
 void vcpu_wake(struct vcpu *v);
 long vcpu_yield(void);
 void vcpu_sleep_nosync(struct vcpu *v);
-- 
2.17.1