Patch "coresight: Fix reference count for software sources" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

coresight: Fix reference count for software sources

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
coresight-fix-reference-count-for-software-sources.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Suzuki K Poulose <[email protected]>
Date: Mon, 5 Jun 2017 14:15:03 -0600
Subject: coresight: Fix reference count for software sources

From: Suzuki K Poulose <[email protected]>

[ Upstream commit 022aa1a81b778789ee7cf3124595854276a0330d ]

For software sources (i.e STM), there could be multiple agents generating the trace data, unlike the ETMs. So we need to properly do the accounting for the active number of users to disable the device when the last user goes away. Right now, the reference counting is broken for sources as we skip the actions when we detect that the source is enabled.

This patch fixes the problem by adding the refcounting for software sources, even when they are enabled.

---
 drivers/hwtracing/coresight/coresight.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

@@ -498,6 +498,9 @@ int coresight_enable(struct coresight_de
 {
 	int cpu, ret = 0;
 	struct list_head *path;
+	enum coresight_dev_subtype_source subtype;
+
+	subtype = csdev->subtype.source_subtype;
 
 	mutex_lock(&coresight_mutex);
 

@@ -505,8 +508,16 @@ int coresight_enable(struct coresight_de
 	if (ret)
 		goto out;
 
-	if (csdev->enable)
+	if (csdev->enable) {
+		/*
+		 * There could be multiple applications driving the software
+		 * source. So keep the refcount for each such user when the
+		 * source is already enabled.
+		 */
+		if (subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE)
+			atomic_inc(csdev->refcnt);
 		goto out;
+	}
 
 	path = coresight_build_path(csdev);
 	if (IS_ERR(path)) {

@@ -523,7 +534,7 @@ int coresight_enable(struct coresight_de
 	if (ret)
 		goto err_source;
 
-	switch (csdev->subtype.source_subtype) {
+	switch (subtype) {
 	case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
 		/*
 		 * When working from sysFS it is important to keep track

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/coresight-fix-reference-count-for-software-sources.patch queue-4.9/coresight-tmc-configure-dma-mask-appropriately.patch