[PATCH v6 05/14] gtrace: Add functions to start/stop tracing on a component path

[Mayuresh Chitale]

The perf driver framework needs to be able to start / stop all components
in a trace component path during its operation. Add gtrace_path_start()
and gtrace_path_stop() functions for this purpose.

Co-developed-by: Anup Patel <anup.patel@xxxxxxxxxxxxxxxx>
Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxxxxxx>
Signed-off-by: Mayuresh Chitale <mayuresh.chitale@xxxxxxxxxxxxxxxx>
---
 drivers/hwtracing/gtrace/gtrace-core.c | 104 +++++++++++++++++++++++++
 include/linux/gtrace.h                 |   7 ++
 2 files changed, 111 insertions(+)

diff --git a/drivers/hwtracing/gtrace/gtrace-core.c b/drivers/hwtracing/gtrace/gtrace-core.c
index f750025104ec..d7f1df90aa31 100644
--- a/drivers/hwtracing/gtrace/gtrace-core.c
+++ b/drivers/hwtracing/gtrace/gtrace-core.c
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/percpu.h>
+#include <linux/spinlock.h>
 #include <linux/xarray.h>
 #include <linux/gtrace.h>
 
@@ -24,7 +25,15 @@ static DEFINE_PER_CPU(struct gtrace_component *, gtrace_cpu_source_comp);
 /* gtrace comp specific data, to be used by core functions only */
 struct gtrace_comp_priv {
 	struct gtrace_component comp;
+	/*
+	 * Protects start_count and owner. Serializes start/stop against other paths
+	 * sharing this component and, for a sink, against gtrace_path_copyto_auxbuf().
+	 * Raw because the PMU start/stop callbacks are called with the rq_lock held.
+	 */
+	raw_spinlock_t lock;
 	u32 type_idx;
+	u32 start_count;
+	pid_t owner;
 	bool ready;
 	bool visited;
 };
@@ -418,6 +427,7 @@ struct gtrace_component *gtrace_register_component(struct gtrace_component_id *i
 		ret = -ENOMEM;
 		goto err_out;
 	}
+	raw_spin_lock_init(&cpriv->lock);
 	comp = &cpriv->comp;
 	comp->pdata = pdata;
 	comp->id = *id;
@@ -611,6 +621,100 @@ static void gtrace_release_path_nodes(struct gtrace_path *path)
 	}
 }
 
+static int __gtrace_comp_start(struct gtrace_component *comp, pid_t owner)
+{
+	struct gtrace_comp_priv *cpriv = to_gtrace_comp_priv(comp);
+	const struct gtrace_driver *gtdrv = to_gtrace_driver(comp->dev.driver);
+	unsigned long flags;
+	int ret = 0;
+
+	if (!gtdrv)
+		return -ENODEV;
+
+	raw_spin_lock_irqsave(&cpriv->lock, flags);
+	if (cpriv->start_count) {
+		if (cpriv->owner != owner) {
+			ret = -EBUSY;
+			goto out;
+		}
+	} else {
+		if (gtdrv->start) {
+			ret = gtdrv->start(comp);
+			if (ret)
+				goto out;
+		}
+		cpriv->owner = owner;
+	}
+
+	cpriv->start_count++;
+out:
+	raw_spin_unlock_irqrestore(&cpriv->lock, flags);
+	return ret;
+}
+
+static int __gtrace_comp_stop(struct gtrace_component *comp)
+{
+	struct gtrace_comp_priv *cpriv = to_gtrace_comp_priv(comp);
+	const struct gtrace_driver *gtdrv = to_gtrace_driver(comp->dev.driver);
+	unsigned long flags;
+	int ret = 0;
+
+	raw_spin_lock_irqsave(&cpriv->lock, flags);
+	if (!cpriv->start_count) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	cpriv->start_count--;
+	if (!cpriv->start_count) {
+		if (!gtdrv) {
+			ret = -ENODEV;
+			goto out;
+		}
+
+		if (gtdrv->stop)
+			ret = gtdrv->stop(comp);
+	}
+out:
+	raw_spin_unlock_irqrestore(&cpriv->lock, flags);
+	return ret;
+}
+
+int gtrace_path_start(struct gtrace_path *path)
+{
+	struct gtrace_path_node *node;
+	int ret = 0;
+
+	list_for_each_entry_reverse(node, &path->comp_list, head) {
+		ret = __gtrace_comp_start(node->comp, path->owner);
+		if (ret)
+			break;
+	}
+
+	/* If a component failed to start, stop all the components that were started before it */
+	if (ret)
+		list_for_each_entry_continue(node, &path->comp_list, head)
+			__gtrace_comp_stop(node->comp);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gtrace_path_start);
+
+int gtrace_path_stop(struct gtrace_path *path)
+{
+	struct gtrace_path_node *node;
+	int ret = 0, err;
+
+	list_for_each_entry(node, &path->comp_list, head) {
+		err = __gtrace_comp_stop(node->comp);
+		if (err && !ret)
+			ret = err;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gtrace_path_stop);
+
 struct gtrace_path *gtrace_create_path(struct gtrace_component *source,
 				       struct gtrace_component *sink,
 				       enum gtrace_component_mode mode)
diff --git a/include/linux/gtrace.h b/include/linux/gtrace.h
index 2c3be4d161c6..a4b99c87d250 100644
--- a/include/linux/gtrace.h
+++ b/include/linux/gtrace.h
@@ -254,6 +254,7 @@ struct gtrace_path {
 	enum gtrace_component_mode	mode;
 	u32				trace_id;
 #define GTRACE_INVALID_TRACE_ID	0
+	pid_t				owner;
 };
 
 struct gtrace_component *gtrace_path_source(struct gtrace_path *path);
@@ -262,10 +263,14 @@ struct gtrace_path *gtrace_create_path(struct gtrace_component *source,
 				       struct gtrace_component *sink,
 				       enum gtrace_component_mode mode);
 void gtrace_destroy_path(struct gtrace_path *path);
+int gtrace_path_start(struct gtrace_path *path);
+int gtrace_path_stop(struct gtrace_path *path);
 
 /**
  * struct gtrace_driver - Representation of a trace driver.
  * @id_table:      Table to match components handled by the driver.
+ * @start:         Callback to start tracing.
+ * @stop:          Callback to stop tracing.
  * @probe:         Driver probe() function.
  * @remove:        Driver remove() function.
  * @get_trace_id:  Get/allocate a trace ID.
@@ -274,6 +279,8 @@ void gtrace_destroy_path(struct gtrace_path *path);
  */
 struct gtrace_driver {
 	const struct gtrace_component_id *id_table;
+	int			(*start)(struct gtrace_component *comp);
+	int			(*stop)(struct gtrace_component *comp);
 	int			(*probe)(struct gtrace_component *comp);
 	void			(*remove)(struct gtrace_component *comp);
 	int			(*get_trace_id)(struct gtrace_component *comp,
-- 
2.43.0