New subject: [PATCH v2] coresight: core: Fix coresight device probe failure issue

8 Mar 2022

Hi Jinlong
On 04/03/2022 08:23, Mao Jinlong wrote:
...
It is possibe that probe failure issue happens when the device
and its child_device's probe happens at the same time.
In coresight_make_links, has_conns_grp is true for parent, but
has_conns_grp is false for child device as has_conns_grp is set
to true in coresight_create_conns_sysfs_group. The probe of parent
device will fail at this condition. Add has_conns_grp check for
child device before make the links and make the process from
device_register to connection_create be atomic to avoid this
probe failure issue.
Suggested-by: Suzuki K Poulose suzuki.poulose@arm.com
Suggested-by: Mike Leach mike.leach@linaro.org
Signed-off-by: Mao Jinlong quic_jinlmao@quicinc.com

drivers/hwtracing/coresight/coresight-core.c | 12 ++++++------
  1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 88653d1c06a4..b3e3bc59c09b 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1382,7 +1382,7 @@ static int coresight_fixup_device_conns(struct coresight_device *csdev)
   		continue;
   	conn->child_dev =
   		coresight_find_csdev_by_fwnode(conn->child_fwnode);

if (conn->child_dev) {




if (conn->child_dev && conn->child_dev->has_conns_grp) {
ret = coresight_make_links(csdev, conn,
			   conn->child_dev);
if (ret)



@@ -1594,7 +1594,8 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
   refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
   if (!refcnts) {
   	ret = -ENOMEM;

goto err_free_csdev;




kfree(csdev);


goto err_out;

}

csdev->refcnt = refcnts;
@@ -1619,8 +1620,10 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
   csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
   dev_set_name(&csdev->dev, "%s", desc->name);

mutex_lock(&coresight_mutex);
ret = device_register(&csdev->dev);
if (ret) {
mutex_unlock(&coresight_mutex);

put_device(&csdev->dev);
/*
All resources are free'd explicitly via



@@ -1634,6 +1637,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
   	ret = etm_perf_add_symlink_sink(csdev);
  
   	if (ret) {

	mutex_unlock(&coresight_mutex);
device_unregister(&csdev->dev);
/*
 * As with the above, all resources are free'd



@@ -1645,8 +1649,6 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
   	}
   }

mutex_lock(&coresight_mutex);
ret = coresight_create_conns_sysfs_group(csdev);
 if (!ret)
  ret = coresight_fixup_device_conns(csdev);

@@ -1663,8 +1665,6 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
  
   return csdev;
  
-err_free_csdev:

kfree(csdev);
err_out:
/* Cleanup the connection information */
coresight_release_platform_data(NULL, desc->pdata);

Could we consolidate the unlock sequence to a single point with 
something like this (untested):
diff --git a/drivers/hwtracing/coresight/coresight-core.c 
b/drivers/hwtracing/coresight/coresight-core.c
index af00dca8d1ac..198ee140c6e6 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1571,6 +1571,7 @@ struct coresight_device *coresight_register(struct 
coresight_desc *desc)
    int nr_refcnts = 1;
    atomic_t *refcnts = NULL;
    struct coresight_device *csdev;
+	bool registered = false;
csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
    if (!csdev) {
@@ -1591,7 +1592,8 @@ struct coresight_device *coresight_register(struct 
coresight_desc *desc)
    refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
    if (!refcnts) {
    	ret = -ENOMEM;
-		goto err_free_csdev;
+		kfree(csdev);
+		goto err_out;
    }
csdev->refcnt = refcnts;
@@ -1616,6 +1618,13 @@ struct coresight_device 
*coresight_register(struct coresight_desc *desc)
    csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
    dev_set_name(&csdev->dev, "%s", desc->name);
+	/*
+	 * Make sure the device registration and the connection fixup
+	 * are synchronised, so that we don't see uninitialised devices
+	 * on the coresight bus while trying to resolve the connections.
+	 */
+	mutex_lock(&coresight_mutex);
+
    ret = device_register(&csdev->dev);
    if (ret) {
    	put_device(&csdev->dev);
@@ -1623,7 +1632,7 @@ struct coresight_device *coresight_register(struct 
coresight_desc *desc)
    	 * All resources are free'd explicitly via
    	 * coresight_device_release(), triggered from put_device().
    	 */
-		goto err_out;
+		goto out_unlock;
    }
if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
@@ -1638,11 +1647,11 @@ struct coresight_device 
*coresight_register(struct coresight_desc *desc)
    		 * from put_device(), which is in turn called from
    		 * function device_unregister().
    		 */
-			goto err_out;
+			goto out_unlock;
    	}
    }
-
-	mutex_lock(&coresight_mutex);
+	/* Device is now registered */
+	registered = true;
ret = coresight_create_conns_sysfs_group(csdev);
    if (!ret)
@@ -1652,16 +1661,15 @@ struct coresight_device 
*coresight_register(struct coresight_desc *desc)
    if (!ret && cti_assoc_ops && cti_assoc_ops->add)
    	cti_assoc_ops->add(csdev);
+out_unlock:
    mutex_unlock(&coresight_mutex);
-	if (ret) {
+	/* Success */
+	if (!ret)
+		return csdev;
+
+	/* Unregister the device if needed */
+	if (registered)
    	coresight_unregister(csdev);
-		return ERR_PTR(ret);
-	}
-
-	return csdev;
-
-err_free_csdev:
-	kfree(csdev);
  err_out:
    /* Cleanup the connection information */
    coresight_release_platform_data(NULL, desc->pdata);
-- 
2.35.1

    

Re: [PATCH v2] coresight: core: Fix coresight device probe failure issue