From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 9 Jan 2024 15:36:31 +0000 (-0500)
Subject: Inline implementation of task_prio()
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ff024e6646f0d75935e8eb277cce508c593a23ad;p=lttng-modules.git

Inline implementation of task_prio()

The task_prio() function has been implemented as "return p->prio -
MAX_RT_PRIO;" since at least kernel v3.0, so inline it into
lttng-modules rather than using kallsyms to call the kernel
implementation.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I7dd482a2da72a005c16b3e5864767b47d7bc3fd3
---

diff --git a/include/lttng/events-internal.h b/include/lttng/events-internal.h
index 181b7b45..a727230f 100644
--- a/include/lttng/events-internal.h
+++ b/include/lttng/events-internal.h
@@ -649,7 +649,6 @@ int lttng_add_pid_to_ctx(struct lttng_kernel_ctx **ctx);
 int lttng_add_cpu_id_to_ctx(struct lttng_kernel_ctx **ctx);
 int lttng_add_procname_to_ctx(struct lttng_kernel_ctx **ctx);
 int lttng_add_prio_to_ctx(struct lttng_kernel_ctx **ctx);
-int wrapper_task_prio_init(void);
 int lttng_add_nice_to_ctx(struct lttng_kernel_ctx **ctx);
 int lttng_add_vpid_to_ctx(struct lttng_kernel_ctx **ctx);
 int lttng_add_tid_to_ctx(struct lttng_kernel_ctx **ctx);
diff --git a/src/lttng-context-prio.c b/src/lttng-context-prio.c
index aac10a63..cbe94800 100644
--- a/src/lttng-context-prio.c
+++ b/src/lttng-context-prio.c
@@ -14,34 +14,16 @@
 #include <lttng/events-internal.h>
 #include <ringbuffer/frontend_types.h>
 #include <wrapper/vmalloc.h>
-#include <wrapper/kallsyms.h>
 #include <lttng/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_funcptr("task_prio");
-	if (!wrapper_task_prio_sym) {
-		printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
-		return -EINVAL;
-	}
-	return 0;
-}
-EXPORT_SYMBOL_GPL(wrapper_task_prio_init);
-
 /*
- * Canary function to check for 'task_prio()' at compile time.
- *
- * From 'include/linux/sched.h':
- *
- *   extern int task_prio(const struct task_struct *p);
+ * task_prio() has been implemented as p->prio - MAX_RT_PRIO since at
+ * least kernel v3.0.
  */
-__attribute__((unused)) static
-int __canary__task_prio(const struct task_struct *p)
+static
+int wrapper_task_prio(struct task_struct *p)
 {
-	return task_prio(p);
+	return p->prio - MAX_RT_PRIO;
 }
 
 static
@@ -61,7 +43,7 @@ void prio_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
 {
 	int prio;
 
-	prio = wrapper_task_prio_sym(current);
+	prio = wrapper_task_prio(current);
 	chan->ops->event_write(ctx, &prio, sizeof(prio), lttng_alignof(prio));
 }
 
@@ -70,7 +52,7 @@ void prio_get_value(void *priv,
 		struct lttng_kernel_probe_ctx *lttng_probe_ctx,
 		struct lttng_ctx_value *value)
 {
-	value->u.s64 = wrapper_task_prio_sym(current);
+	value->u.s64 = wrapper_task_prio(current);
 }
 
 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
diff --git a/src/lttng-events.c b/src/lttng-events.c
index 08884410..a0bd2322 100644
--- a/src/lttng-events.c
+++ b/src/lttng-events.c
@@ -4148,9 +4148,6 @@ static int __init lttng_events_init(void)
 	int ret;
 
 	ret = wrapper_get_pfnblock_flags_mask_init();
-	if (ret)
-		return ret;
-	ret = wrapper_task_prio_init();
 	if (ret)
 		return ret;
 	ret = lttng_probes_init();