[PATCH 3/4] coresight: etb10: Prevent per-thread events from sharing a sink

[James Clark <james.clark@linaro.org>]

Like the previous commit to ETR, ETB10 sinks shouldn't share per-thread
events. Fix it by returning -EBUSY if a second per-thread event tries to
use the same sink.

Fixes: 75d7dbd38824 ("coresight: etb10: Add support for CPU-wide trace scenarios")
Signed-off-by: James Clark <james.clark@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 30 +++++++--------------------
 1 file changed, 8 insertions(+), 22 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index a827f76b8144..6b5caad330d9 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -71,8 +71,7 @@
  * @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.
+ * @event:	Perf event using this sink if in Perf mode.
  * @buf:	area of memory where ETB buffer content gets sent.
  * @buffer_depth: size of @buf.
  * @trigger_cntr: amount of words to store after a trigger.
@@ -84,7 +83,7 @@ struct etb_drvdata {
 	struct miscdevice	miscdev;
 	raw_spinlock_t		spinlock;
 	atomic_t		reading;
-	pid_t			pid;
+	struct perf_event	*event;
 	u8			*buf;
 	u32			buffer_depth;
 	u32			trigger_cntr;
@@ -168,11 +167,9 @@ static int etb_enable_sysfs(struct coresight_device *csdev)
 static int etb_enable_perf(struct coresight_device *csdev, struct coresight_path *path)
 {
 	int ret = 0;
-	pid_t pid;
 	unsigned long flags;
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct perf_output_handle *handle = path->handle;
-	struct cs_buffers *buf = etm_perf_sink_config(handle);
 
 	raw_spin_lock_irqsave(&drvdata->spinlock, flags);
 
@@ -182,19 +179,14 @@ static int etb_enable_perf(struct coresight_device *csdev, struct coresight_path
 		goto out;
 	}
 
-	/* Get a handle on the pid of the process to monitor */
-	pid = buf->pid;
-
-	if (drvdata->pid != -1 && drvdata->pid != pid) {
+	if (drvdata->event &&
+	    !coresight_sink_can_share(drvdata->event, handle->event)) {
 		ret = -EBUSY;
 		goto out;
 	}
 
-	/*
-	 * No HW configuration is needed if the sink is already in
-	 * use for this session.
-	 */
-	if (drvdata->pid == pid) {
+	/*  No HW configuration is needed if the sink is already in use. */
+	if (csdev->refcnt) {
 		csdev->refcnt++;
 		goto out;
 	}
@@ -210,8 +202,7 @@ static int etb_enable_perf(struct coresight_device *csdev, struct coresight_path
 
 	ret = etb_enable_hw(drvdata);
 	if (!ret) {
-		/* Associate with monitored process. */
-		drvdata->pid = pid;
+		drvdata->event = handle->event;
 		coresight_set_mode(drvdata->csdev, CS_MODE_PERF);
 		csdev->refcnt++;
 	}
@@ -361,8 +352,7 @@ static int etb_disable(struct coresight_device *csdev)
 	/* Complain if we (somehow) got out of sync */
 	WARN_ON_ONCE(coresight_get_mode(csdev) == CS_MODE_DISABLED);
 	etb_disable_hw(drvdata);
-	/* Dissociate from monitored process. */
-	drvdata->pid = -1;
+	drvdata->event = NULL;
 	coresight_set_mode(csdev, CS_MODE_DISABLED);
 	raw_spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -383,7 +373,6 @@ static void *etb_alloc_buffer(struct coresight_device *csdev,
 	if (!buf)
 		return NULL;
 
-	buf->pid = task_pid_nr(event->owner);
 	buf->snapshot = overwrite;
 	buf->nr_pages = nr_pages;
 	buf->data_pages = pages;
@@ -754,9 +743,6 @@ 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;
-
 	pdata = coresight_get_platform_data(dev);
 	if (IS_ERR(pdata))
 		return PTR_ERR(pdata);

-- 
2.34.1