1 files changed, 39 insertions, 4 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index eeae375c7aed..4ee4c80a4354 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -72,6 +72,8 @@
  * @miscdev:	specifics to handle "/dev/xyz.etb" entry.
  * @spinlock:	only one at a time pls.
  * @reading:	synchronise user space access to etb buffer.
+ * @pid:	Process ID of the process being monitored by the session
+ *		that is using this component.
  * @buf:	area of memory where ETB buffer content gets sent.
  * @mode:	this ETB is being used.
  * @buffer_depth: size of @buf.
@@ -85,6 +87,7 @@ struct etb_drvdata {
 	struct miscdevice	miscdev;
 	spinlock_t		spinlock;
 	local_t			reading;
+	pid_t			pid;
 	u8			*buf;
 	u32			mode;
 	u32			buffer_depth;
@@ -169,28 +172,49 @@ out:
 static int etb_enable_perf(struct coresight_device *csdev, void *data)
 {
 	int ret = 0;
+	pid_t pid;
 	unsigned long flags;
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+	struct perf_output_handle *handle = data;
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
-	/* No need to continue if the component is already in use. */
-	if (drvdata->mode != CS_MODE_DISABLED) {
+	/* No need to continue if the component is already in used by sysFS. */
+	if (drvdata->mode == CS_MODE_SYSFS) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/* Get a handle on the pid of the process to monitor */
+	pid = task_pid_nr(handle->event->owner);
+
+	if (drvdata->pid != -1 && drvdata->pid != pid) {
 		ret = -EBUSY;
 		goto out;
 	}
 
 	/*
+	 * No HW configuration is needed if the sink is already in
+	 * use for this session.
+	 */
+	if (drvdata->pid == pid) {
+		atomic_inc(csdev->refcnt);
+		goto out;
+	}
+
+	/*
 	 * We don't have an internal state to clean up if we fail to setup
 	 * the perf buffer. So we can perform the step before we turn the
 	 * ETB on and leave without cleaning up.
 	 */
-	ret = etb_set_buffer(csdev, (struct perf_output_handle *)data);
+	ret = etb_set_buffer(csdev, handle);
 	if (ret)
 		goto out;
 
 	ret = etb_enable_hw(drvdata);
 	if (!ret) {
+		/* Associate with monitored process. */
+		drvdata->pid = pid;
 		drvdata->mode = CS_MODE_PERF;
 		atomic_inc(csdev->refcnt);
 	}
@@ -336,6 +360,8 @@ static int etb_disable(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(drvdata->mode == CS_MODE_DISABLED);
 	etb_disable_hw(drvdata);
+	/* Dissociate from monitored process. */
+	drvdata->pid = -1;
 	drvdata->mode = CS_MODE_DISABLED;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -406,7 +432,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	const u32 *barrier;
 	u32 read_ptr, write_ptr, capacity;
 	u32 status, read_data;
-	unsigned long offset, to_read, flags;
+	unsigned long offset, to_read = 0, flags;
 	struct cs_buffers *buf = sink_config;
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -416,6 +442,11 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
+
+	/* Don't do anything if another tracer is using this sink */
+	if (atomic_read(csdev->refcnt) != 1)
+		goto out;
+
 	__etb_disable_hw(drvdata);
 	CS_UNLOCK(drvdata->base);
 
@@ -526,6 +557,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 	}
 	__etb_enable_hw(drvdata);
 	CS_LOCK(drvdata->base);
+out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	return to_read;
@@ -733,6 +765,9 @@ static int etb_probe(struct amba_device *adev, const struct amba_id *id)
 	if (!drvdata->buf)
 		return -ENOMEM;
 
+	/* This device is not associated with a session */
+	drvdata->pid = -1;
+
 	desc.type = CORESIGHT_DEV_TYPE_SINK;
 	desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
 	desc.ops = &etb_cs_ops;