Re: [PATCH] pata_legacy: Allow disabling of legacy PATA device probes on non-PCI systems

[Tejun Heo <tj@kernel.org>]

On Wed, Jan 11, 2017 at 08:54:21PM -0500, tedheadster wrote:
> ​Tejun,
>   I'm interested in debugging this. What can I do to help?

Sorry about taking so long.  I suck. :)

Can you please try the following patch and post what the kernel prints
out?

Thanks.
---
 drivers/ata/pata_legacy.c |    2 ++
 drivers/base/core.c       |    9 +++++++++
 include/linux/kobject.h   |    1 +
 lib/kobject.c             |   22 ++++++++++++++++++++++
 4 files changed, 34 insertions(+)

--- a/drivers/ata/pata_legacy.c
+++ b/drivers/ata/pata_legacy.c
@@ -962,6 +962,8 @@ static __init int legacy_init_one(struct
 	if (IS_ERR(pdev))
 		return PTR_ERR(pdev);
 
+	pdev->dev.kobj.release_debug = true;
+
 	ret = -EBUSY;
 	if (devm_request_region(&pdev->dev, io, 8, "pata_legacy") == NULL ||
 	    devm_request_region(&pdev->dev, io + 0x0206, 1,
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -803,8 +803,17 @@ static void device_release(struct kobjec
 	 * is deleted but alive, so release devres here to avoid
 	 * possible memory leak.
 	 */
+	if (kobj->release_debug)
+		dev_info(dev, "XXX device_release: drel=%pf trel=%pf cdrel=%pf\n",
+			 dev->release,
+			 dev->type ? dev->type->release : NULL,
+			 dev->class ? dev->class->dev_release : NULL);
+
 	devres_release_all(dev);
 
+	if (kobj->release_debug)
+		dev_info(dev, "XXX device_release: devres_release_all() done\n");
+
 	if (dev->release)
 		dev->release(dev);
 	else if (dev->type && dev->type->release)
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -76,6 +76,7 @@ struct kobject {
 	unsigned int state_add_uevent_sent:1;
 	unsigned int state_remove_uevent_sent:1;
 	unsigned int uevent_suppress:1;
+	unsigned int release_debug:1;
 };
 
 extern __printf(2, 3)
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -595,6 +595,13 @@ struct kobject *kobject_get(struct kobje
 			WARN(1, KERN_WARNING "kobject: '%s' (%p): is not "
 			       "initialized, yet kobject_get() is being "
 			       "called.\n", kobject_name(kobj), kobj);
+		if (kobj->release_debug)
+			printk("XXX kobject_get(%s): ref=%d++ (%pf:%pf:%pf)\n",
+			       kobject_name(kobj),
+			       atomic_read(&kobj->kref.refcount),
+			       __builtin_return_address(1),
+			       __builtin_return_address(2),
+			       __builtin_return_address(3));
 		kref_get(&kobj->kref);
 	}
 	return kobj;
@@ -620,6 +627,14 @@ static void kobject_cleanup(struct kobje
 	pr_debug("kobject: '%s' (%p): %s, parent %p\n",
 		 kobject_name(kobj), kobj, __func__, kobj->parent);
 
+	if (kobj->release_debug)
+		printk("XXX kobject_cleanup(%s): rel=%pf (%pf:%pf:%pf)\n",
+		       kobject_name(kobj),
+		       (t && t->release) ? t->release : NULL,
+		       __builtin_return_address(1),
+		       __builtin_return_address(2),
+		       __builtin_return_address(3));
+
 	if (t && !t->release)
 		pr_debug("kobject: '%s' (%p): does not have a release() "
 			 "function, it is broken and must be fixed.\n",
@@ -688,6 +703,13 @@ void kobject_put(struct kobject *kobj)
 			WARN(1, KERN_WARNING "kobject: '%s' (%p): is not "
 			       "initialized, yet kobject_put() is being "
 			       "called.\n", kobject_name(kobj), kobj);
+		if (kobj->release_debug)
+			printk("XXX kobject_put(%s): ref=%d-- (%pf:%pf:%pf)\n",
+			       kobject_name(kobj),
+			       atomic_read(&kobj->kref.refcount),
+			       __builtin_return_address(1),
+			       __builtin_return_address(2),
+			       __builtin_return_address(3));
 		kref_put(&kobj->kref, kobject_release);
 	}
 }