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

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

Like the previous commit to ETR, SMB 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: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver")
Signed-off-by: James Clark <james.clark@linaro.org>
---
 drivers/hwtracing/coresight/coresight-priv.h |  2 --
 drivers/hwtracing/coresight/ultrasoc-smb.c   | 22 ++++++----------------
 drivers/hwtracing/coresight/ultrasoc-smb.h   |  5 ++---
 3 files changed, 8 insertions(+), 21 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index dddac946659f..492f050eb698 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -94,7 +94,6 @@ enum etm_addr_type {
  * struct cs_buffer - keep track of a recording session' specifics
  * @cur:	index of the current buffer
  * @nr_pages:	max number of pages granted to us
- * @pid:	PID this cs_buffer belongs to
  * @offset:	offset within the current buffer
  * @data_size:	how much we collected in this run
  * @snapshot:	is this run in snapshot mode
@@ -103,7 +102,6 @@ enum etm_addr_type {
 struct cs_buffers {
 	unsigned int		cur;
 	unsigned int		nr_pages;
-	pid_t			pid;
 	unsigned long		offset;
 	local_t			data_size;
 	bool			snapshot;
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index 20a950b9dd4f..12d2f855de25 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -216,22 +216,15 @@ static int smb_enable_perf(struct coresight_device *csdev,
 {
 	struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct perf_output_handle *handle = path->handle;
-	struct cs_buffers *buf = etm_perf_sink_config(handle);
-	pid_t pid;
 
-	if (!buf)
-		return -EINVAL;
-
-	/* Get a handle on the pid of the target process */
-	pid = buf->pid;
-
-	/* Device is already in used by other session */
-	if (drvdata->pid != -1 && drvdata->pid != pid)
+	/* Do not proceed if this device is associated with another session */
+	if (drvdata->event &&
+	    !coresight_sink_can_share(drvdata->event, handle->event))
 		return -EBUSY;
 
-	if (drvdata->pid == -1) {
+	if (!drvdata->event) {
 		smb_enable_hw(drvdata);
-		drvdata->pid = pid;
+		drvdata->event = handle->event;
 		coresight_set_mode(csdev, CS_MODE_PERF);
 	}
 
@@ -293,8 +286,7 @@ static int smb_disable(struct coresight_device *csdev)
 
 	smb_disable_hw(drvdata);
 
-	/* Dissociate from the target process. */
-	drvdata->pid = -1;
+	drvdata->event = NULL;
 	coresight_set_mode(csdev, CS_MODE_DISABLED);
 	dev_dbg(&csdev->dev, "Ultrasoc SMB disabled\n");
 
@@ -316,7 +308,6 @@ static void *smb_alloc_buffer(struct coresight_device *csdev,
 	buf->snapshot = overwrite;
 	buf->nr_pages = nr_pages;
 	buf->data_pages = pages;
-	buf->pid = task_pid_nr(event->owner);
 
 	return buf;
 }
@@ -564,7 +555,6 @@ static int smb_probe(struct platform_device *pdev)
 	smb_reset_buffer(drvdata);
 	platform_set_drvdata(pdev, drvdata);
 	raw_spin_lock_init(&drvdata->spinlock);
-	drvdata->pid = -1;
 
 	ret = smb_register_sink(pdev, drvdata);
 	if (ret) {
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
index 323f0ccb6878..5129afa1dfc8 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.h
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
@@ -108,8 +108,7 @@ struct smb_data_buffer {
  * @miscdev:	Specifics to handle "/dev/xyz.smb" entry.
  * @spinlock:	Control data access to one at a time.
  * @reading:	Synchronise user space access to SMB 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.
  */
 struct smb_drv_data {
 	void __iomem *base;
@@ -118,7 +117,7 @@ struct smb_drv_data {
 	struct miscdevice miscdev;
 	raw_spinlock_t spinlock;
 	bool reading;
-	pid_t pid;
+	struct perf_event *event;
 };
 
 #endif

-- 
2.34.1