Prio context: fix symbol lookup

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Makefile

@@ -13,8 +13,7 @@ obj-m += ltt-relay.o
 ltt-relay-objs :=  ltt-events.o ltt-debugfs-abi.o \
 			ltt-probes.o ltt-core.o ltt-context.o \
 			lttng-context-pid.o lttng-context-comm.o \
-			lttng-context-prio.o lttng-context-nice.o \
-			wrapper/sched.o
+			lttng-context-prio.o lttng-context-nice.o
 
 obj-m += probes/
 obj-m += lib/

ltt-events.c

@@ -860,9 +860,6 @@ static int __init ltt_events_init(void)
 {
 	int ret;
 
-	ret = wrapper_task_prio_init();
-	if (ret)
-		return ret;
 	event_cache = KMEM_CACHE(ltt_event, 0);
 	if (!event_cache)
 		return -ENOMEM;

ltt-events.h

@@ -272,10 +272,6 @@ int ltt_probes_init(void);
 void ltt_probes_exit(void);
 struct lttng_ctx_field *lttng_append_context(struct lttng_ctx **ctx);
 void lttng_destroy_context(struct lttng_ctx *ctx);
-
-int wrapper_task_prio_init(void);
-int wrapper_task_prio_sym(struct task_struct *t);
-
 int lttng_add_pid_to_ctx(struct lttng_ctx **ctx);
 int lttng_add_comm_to_ctx(struct lttng_ctx **ctx);
 int lttng_add_prio_to_ctx(struct lttng_ctx **ctx);

lttng-context-prio.c

@@ -15,6 +15,19 @@
 #include "wrapper/vmalloc.h"
 #include "ltt-tracer.h"
 
+static
+int (*wrapper_task_prio_sym)(struct task_struct *t);
+
+int wrapper_task_prio_init(void)
+{
+	wrapper_task_prio_sym = (void *) kallsyms_lookup_name("task_prio");
+	if (!wrapper_task_prio_sym) {
+		printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
 static
 size_t prio_get_size(size_t offset)
 {
@@ -42,6 +55,12 @@ int lttng_add_prio_to_ctx(struct lttng_ctx **ctx)
 	struct lttng_ctx_field *field;
 	int ret;
 
+	if (!wrapper_task_prio_sym) {
+		ret = wrapper_task_prio_init();
+		if (ret)
+			return ret;
+	}
+
 	field = lttng_append_context(ctx);
 	if (!field)
 		return ret;