[PATCH v3 0/3] driver core: Add device link related sysfs files

[PATCH v3 0/3] driver core: Add device link related sysfs files

[Saravana Kannan]

With fw_devlink and with sync_state() callback features, there's a lot
of device/device link related information that's not available in sysfs.

Exposing these details to user space can be very useful in understanding
suspend/resume issues, runtime pm issues, probing issues, figuring out
the modules that'd be needed for first stage init, etc. In fact, an
earlier verion of this series was very helpful in debugging and
validating the recent memory leak fix[1].

This series is based on driver-core-next and [1] cherry-picked on top of
it.

[1] - https://lore.kernel.org/lkml/20200519063000.128819-1-saravanak@google.com/

v1->v2:
Patch 1/4
- New patch
Patch 2/4
- Fixed the warnings I saw before that were related to incorrect
  sysfs removal code when a device link is deleted.
- Fixed error handling in device_link_add()
- Split up flags into more meaningful files.
- Added status file.
Patch 3/4
- Fixed error handling that Greg pointed out before.
Patch 4/4
- New patch

v2->v3:
- Dropped patch 1/4 from v2 since it was already picked up. So numbering
  has shifted.
Patch 1/3
- Added documentation

Saravana Kannan (3):
  driver core: Expose device link details in sysfs
  driver core: Add state_synced sysfs file for devices that support it
  driver core: Add waiting_for_supplier sysfs file for devices

 Documentation/ABI/testing/sysfs-class-devlink | 126 ++++++++++
 .../ABI/testing/sysfs-devices-consumer        |   8 +
 .../ABI/testing/sysfs-devices-state_synced    |  24 ++
 .../ABI/testing/sysfs-devices-supplier        |   8 +
 .../sysfs-devices-waiting_for_supplier        |  17 ++
 drivers/base/core.c                           | 237 +++++++++++++++++-
 drivers/base/dd.c                             |  22 ++
 include/linux/device.h                        |  58 ++---
 8 files changed, 464 insertions(+), 36 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-class-devlink
 create mode 100644 Documentation/ABI/testing/sysfs-devices-consumer
 create mode 100644 Documentation/ABI/testing/sysfs-devices-state_synced
 create mode 100644 Documentation/ABI/testing/sysfs-devices-supplier
 create mode 100644 Documentation/ABI/testing/sysfs-devices-waiting_for_supplier

-- 
2.27.0.rc0.183.gde8f92d652-goog

[PATCH v3 1/3] driver core: Expose device link details in sysfs

[Saravana Kannan]

It's helpful to be able to look at device link details from sysfs. So,
expose it in sysfs.

Say device-A is supplier of device-B. These are the additional files
this patch would create:

/sys/class/devlink/device-A:device-B/
	auto_remove_on
	consumer/ -> .../device-B/
	runtime_pm
	status
	supplier/ -> .../device-A/
	sync_state_only

/sys/devices/.../device-A/
	consumer:device-B/ -> /sys/class/devlink/device-A:device-B/

/sys/devices/.../device-B/
	supplier:device-A/ -> /sys/class/devlink/device-A:device-B/

That way:
To get a list of all the device link in the system:
ls /sys/class/devlink/

To get the consumer names and links of a device:
ls -d /sys/devices/.../device-X/consumer:*

To get the supplier names and links of a device:
ls -d /sys/devices/.../device-X/supplier:*

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 Documentation/ABI/testing/sysfs-class-devlink | 126 +++++++++++
 .../ABI/testing/sysfs-devices-consumer        |   8 +
 .../ABI/testing/sysfs-devices-supplier        |   8 +
 drivers/base/core.c                           | 211 +++++++++++++++++-
 include/linux/device.h                        |  58 ++---
 5 files changed, 375 insertions(+), 36 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-class-devlink
 create mode 100644 Documentation/ABI/testing/sysfs-devices-consumer
 create mode 100644 Documentation/ABI/testing/sysfs-devices-supplier

diff --git a/Documentation/ABI/testing/sysfs-class-devlink b/Documentation/ABI/testing/sysfs-class-devlink
new file mode 100644
index 000000000000..3a24973abb83
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-devlink
@@ -0,0 +1,126 @@
+What:		/sys/class/devlink/.../
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		Provide a place in sysfs for the device link objects in the
+		kernel at any given time.  The name of a device link directory,
+		denoted as ... above, is of the form <supplier>:<consumer>
+		where <supplier> is the supplier device name and <consumer> is
+		the consumer device name.
+
+What:		/sys/class/devlink/.../auto_remove_on
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		This file indicates if the device link will ever be
+		automatically removed by the driver core when the consumer and
+		supplier devices themselves are still present.
+
+		This will be one of the following strings:
+
+		'consumer unbind'
+		'supplier unbind'
+		'never'
+
+		'consumer unbind' means the device link will be removed when
+		the consumer's driver is unbound from the consumer device.
+
+		'supplier unbind' means the device link will be removed when
+		the supplier's driver is unbound from the supplier device.
+
+		'never' means the device link will not be automatically removed
+		when as long as the supplier and consumer devices themselves
+		are still present.
+
+What:		/sys/class/devlink/.../consumer
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		This file is a symlink to the consumer device's sysfs directory.
+
+What:		/sys/class/devlink/.../runtime_pm
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		This file indicates if the device link has any impact on the
+		runtime power management behavior of the consumer and supplier
+		devices. For example: Making sure the supplier doesn't enter
+		runtime suspend while the consumer is active.
+
+		This will be one of the following strings:
+
+		'0' - Does not affect runtime power management
+		'1' - Affects runtime power management
+
+What:		/sys/class/devlink/.../status
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		This file indicates the status of the device link. The status
+		of a device link is affected by whether the supplier and
+		consumer devices have been bound to their corresponding
+		drivers. The status of a device link also affects the binding
+		and unbinding of the supplier and consumer devices with their
+		drivers and also affects whether the software state of the
+		supplier device is synced with the hardware state of the
+		supplier device after boot up.
+		See also: sysfs-devices-state_synced.
+
+		This will be one of the following strings:
+
+		'not tracked'
+		'dormant'
+		'available'
+		'consumer probing'
+		'active'
+		'supplier unbinding'
+		'unknown'
+
+		'not tracked' means this device link does not track the status
+		and has no impact on the binding, unbinding and syncing the
+		hardware and software device state.
+
+		'dormant' means the supplier and the consumer devices have not
+		bound to their driver.
+
+		'available' means the supplier has bound to its driver and is
+		available to supply resources to the consumer device.
+
+		'consumer probing' means the consumer device is currently
+		trying to bind to its driver.
+
+		'active' means the supplier and consumer devices have both
+		bound successfully to their drivers.
+
+		'supplier unbinding' means the supplier devices is currently in
+		the process of unbinding from its driver.
+
+		'unknown' means the state of the device link is not any of the
+		above. If this is ever the value, there's a bug in the kernel.
+
+What:		/sys/class/devlink/.../supplier
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		This file is a symlink to the supplier device's sysfs directory.
+
+What:		/sys/class/devlink/.../sync_state_only
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		This file indicates if the device link is limited to only
+		affecting the syncing of the hardware and software state of the
+		supplier device.
+
+		This will be one of the following strings:
+
+		'0'
+		'1' - Affects runtime power management
+
+		'0' means the device link can affect other device behaviors
+		like binding/unbinding, suspend/resume, runtime power
+		management, etc.
+
+		'1' means the device link will only affect the syncing of
+		hardware and software state of the supplier device after boot
+		up and doesn't not affect other behaviors of the devices.
diff --git a/Documentation/ABI/testing/sysfs-devices-consumer b/Documentation/ABI/testing/sysfs-devices-consumer
new file mode 100644
index 000000000000..1f06d74d1c3c
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-consumer
@@ -0,0 +1,8 @@
+What:		/sys/devices/.../consumer:<consumer>
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		The /sys/devices/.../consumer:<consumer> are symlinks to device
+		links where this device is the supplier. <consumer> denotes the
+		name of the consumer in that device link. There can be zero or
+		more of these symlinks for a given device.
diff --git a/Documentation/ABI/testing/sysfs-devices-supplier b/Documentation/ABI/testing/sysfs-devices-supplier
new file mode 100644
index 000000000000..a919e0db5e90
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-supplier
@@ -0,0 +1,8 @@
+What:		/sys/devices/.../supplier:<supplier>
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		The /sys/devices/.../supplier:<supplier> are symlinks to device
+		links where this device is the consumer. <supplier> denotes the
+		name of the supplier in that device link. There can be zero or
+		more of these symlinks for a given device.
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 791b7530599f..81c8ef088d3a 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -235,6 +235,186 @@ void device_pm_move_to_tail(struct device *dev)
 	device_links_read_unlock(idx);
 }
 
+#define to_devlink(dev)	container_of((dev), struct device_link, link_dev)
+
+static ssize_t status_show(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	char *status;
+
+	switch (to_devlink(dev)->status) {
+	case DL_STATE_NONE:
+		status = "not tracked"; break;
+	case DL_STATE_DORMANT:
+		status = "dormant"; break;
+	case DL_STATE_AVAILABLE:
+		status = "available"; break;
+	case DL_STATE_CONSUMER_PROBE:
+		status = "consumer probing"; break;
+	case DL_STATE_ACTIVE:
+		status = "active"; break;
+	case DL_STATE_SUPPLIER_UNBIND:
+		status = "supplier unbinding"; break;
+	default:
+		status = "unknown"; break;
+	}
+	return sprintf(buf, "%s\n", status);
+}
+static DEVICE_ATTR_RO(status);
+
+static ssize_t auto_remove_on_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct device_link *link = to_devlink(dev);
+	char *str;
+
+	if (link->flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
+		str = "supplier unbind";
+	else if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER)
+		str = "consumer unbind";
+	else
+		str = "never";
+
+	return sprintf(buf, "%s\n", str);
+}
+static DEVICE_ATTR_RO(auto_remove_on);
+
+static ssize_t runtime_pm_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct device_link *link = to_devlink(dev);
+
+	return sprintf(buf, "%d\n", !!(link->flags & DL_FLAG_PM_RUNTIME));
+}
+static DEVICE_ATTR_RO(runtime_pm);
+
+static ssize_t sync_state_only_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct device_link *link = to_devlink(dev);
+
+	return sprintf(buf, "%d\n", !!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
+}
+static DEVICE_ATTR_RO(sync_state_only);
+
+static struct attribute *devlink_attrs[] = {
+	&dev_attr_status.attr,
+	&dev_attr_auto_remove_on.attr,
+	&dev_attr_runtime_pm.attr,
+	&dev_attr_sync_state_only.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(devlink);
+
+static void devlink_dev_release(struct device *dev)
+{
+	kfree(to_devlink(dev));
+}
+
+static struct class devlink_class = {
+	.name = "devlink",
+	.owner = THIS_MODULE,
+	.dev_groups = devlink_groups,
+	.dev_release = devlink_dev_release,
+};
+
+static int devlink_add_symlinks(struct device *dev,
+				struct class_interface *class_intf)
+{
+	int ret;
+	size_t len;
+	struct device_link *link = to_devlink(dev);
+	struct device *sup = link->supplier;
+	struct device *con = link->consumer;
+	char *buf;
+
+	len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+	len += strlen("supplier:") + 1;
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = sysfs_create_link(&link->link_dev.kobj, &sup->kobj, "supplier");
+	if (ret)
+		goto out;
+
+	ret = sysfs_create_link(&link->link_dev.kobj, &con->kobj, "consumer");
+	if (ret)
+		goto err_con;
+
+	snprintf(buf, len, "consumer:%s", dev_name(con));
+	ret = sysfs_create_link(&sup->kobj, &link->link_dev.kobj, buf);
+	if (ret)
+		goto err_con_dev;
+
+	snprintf(buf, len, "supplier:%s", dev_name(sup));
+	ret = sysfs_create_link(&con->kobj, &link->link_dev.kobj, buf);
+	if (ret)
+		goto err_sup_dev;
+
+	goto out;
+
+err_sup_dev:
+	snprintf(buf, len, "consumer:%s", dev_name(con));
+	sysfs_remove_link(&sup->kobj, buf);
+err_con_dev:
+	sysfs_remove_link(&link->link_dev.kobj, "consumer");
+err_con:
+	sysfs_remove_link(&link->link_dev.kobj, "supplier");
+out:
+	kfree(buf);
+	return ret;
+}
+
+static void devlink_remove_symlinks(struct device *dev,
+				   struct class_interface *class_intf)
+{
+	struct device_link *link = to_devlink(dev);
+	size_t len;
+	struct device *sup = link->supplier;
+	struct device *con = link->consumer;
+	char *buf;
+
+	sysfs_remove_link(&link->link_dev.kobj, "consumer");
+	sysfs_remove_link(&link->link_dev.kobj, "supplier");
+
+	len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+	len += strlen("supplier:") + 1;
+	buf = kzalloc(len, GFP_KERNEL);
+	if (!buf) {
+		WARN(1, "Unable to properly free device link symlinks!\n");
+		return;
+	}
+
+	snprintf(buf, len, "supplier:%s", dev_name(sup));
+	sysfs_remove_link(&con->kobj, buf);
+	snprintf(buf, len, "consumer:%s", dev_name(con));
+	sysfs_remove_link(&sup->kobj, buf);
+	kfree(buf);
+}
+
+static struct class_interface devlink_class_intf = {
+	.class = &devlink_class,
+	.add_dev = devlink_add_symlinks,
+	.remove_dev = devlink_remove_symlinks,
+};
+
+static int __init devlink_class_init(void)
+{
+	int ret;
+
+	ret = class_register(&devlink_class);
+	if (ret)
+		return ret;
+
+	ret = class_interface_register(&devlink_class_intf);
+	if (ret)
+		class_unregister(&devlink_class);
+
+	return ret;
+}
+postcore_initcall(devlink_class_init);
+
 #define DL_MANAGED_LINK_FLAGS (DL_FLAG_AUTOREMOVE_CONSUMER | \
 			       DL_FLAG_AUTOREMOVE_SUPPLIER | \
 			       DL_FLAG_AUTOPROBE_CONSUMER  | \
@@ -407,13 +587,6 @@ struct device_link *device_link_add(struct device *consumer,
 
 	refcount_set(&link->rpm_active, 1);
 
-	if (flags & DL_FLAG_PM_RUNTIME) {
-		if (flags & DL_FLAG_RPM_ACTIVE)
-			refcount_inc(&link->rpm_active);
-
-		pm_runtime_new_link(consumer);
-	}
-
 	get_device(supplier);
 	link->supplier = supplier;
 	INIT_LIST_HEAD(&link->s_node);
@@ -423,6 +596,25 @@ struct device_link *device_link_add(struct device *consumer,
 	link->flags = flags;
 	kref_init(&link->kref);
 
+	link->link_dev.class = &devlink_class;
+	device_set_pm_not_required(&link->link_dev);
+	dev_set_name(&link->link_dev, "%s:%s",
+		     dev_name(supplier), dev_name(consumer));
+	if (device_register(&link->link_dev)) {
+		put_device(consumer);
+		put_device(supplier);
+		kfree(link);
+		link = NULL;
+		goto out;
+	}
+
+	if (flags & DL_FLAG_PM_RUNTIME) {
+		if (flags & DL_FLAG_RPM_ACTIVE)
+			refcount_inc(&link->rpm_active);
+
+		pm_runtime_new_link(consumer);
+	}
+
 	/* Determine the initial link state. */
 	if (flags & DL_FLAG_STATELESS)
 		link->status = DL_STATE_NONE;
@@ -545,7 +737,7 @@ static void device_link_free(struct device_link *link)
 
 	put_device(link->consumer);
 	put_device(link->supplier);
-	kfree(link);
+	device_unregister(&link->link_dev);
 }
 
 #ifdef CONFIG_SRCU
@@ -1141,6 +1333,9 @@ static void device_links_purge(struct device *dev)
 {
 	struct device_link *link, *ln;
 
+	if (dev->class == &devlink_class)
+		return;
+
 	mutex_lock(&wfs_lock);
 	list_del(&dev->links.needs_suppliers);
 	mutex_unlock(&wfs_lock);
diff --git a/include/linux/device.h b/include/linux/device.h
index ac8e37cd716a..4c10afed9cd6 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -386,34 +386,6 @@ enum device_link_state {
 #define DL_FLAG_MANAGED			BIT(6)
 #define DL_FLAG_SYNC_STATE_ONLY		BIT(7)
 
-/**
- * struct device_link - Device link representation.
- * @supplier: The device on the supplier end of the link.
- * @s_node: Hook to the supplier device's list of links to consumers.
- * @consumer: The device on the consumer end of the link.
- * @c_node: Hook to the consumer device's list of links to suppliers.
- * @status: The state of the link (with respect to the presence of drivers).
- * @flags: Link flags.
- * @rpm_active: Whether or not the consumer device is runtime-PM-active.
- * @kref: Count repeated addition of the same link.
- * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
- * @supplier_preactivated: Supplier has been made active before consumer probe.
- */
-struct device_link {
-	struct device *supplier;
-	struct list_head s_node;
-	struct device *consumer;
-	struct list_head c_node;
-	enum device_link_state status;
-	u32 flags;
-	refcount_t rpm_active;
-	struct kref kref;
-#ifdef CONFIG_SRCU
-	struct rcu_head rcu_head;
-#endif
-	bool supplier_preactivated; /* Owned by consumer probe. */
-};
-
 /**
  * enum dl_dev_state - Device driver presence tracking information.
  * @DL_DEV_NO_DRIVER: There is no driver attached to the device.
@@ -624,6 +596,36 @@ struct device {
 #endif
 };
 
+/**
+ * struct device_link - Device link representation.
+ * @supplier: The device on the supplier end of the link.
+ * @s_node: Hook to the supplier device's list of links to consumers.
+ * @consumer: The device on the consumer end of the link.
+ * @c_node: Hook to the consumer device's list of links to suppliers.
+ * @link_dev: device used to expose link details in sysfs
+ * @status: The state of the link (with respect to the presence of drivers).
+ * @flags: Link flags.
+ * @rpm_active: Whether or not the consumer device is runtime-PM-active.
+ * @kref: Count repeated addition of the same link.
+ * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
+ * @supplier_preactivated: Supplier has been made active before consumer probe.
+ */
+struct device_link {
+	struct device *supplier;
+	struct list_head s_node;
+	struct device *consumer;
+	struct list_head c_node;
+	struct device link_dev;
+	enum device_link_state status;
+	u32 flags;
+	refcount_t rpm_active;
+	struct kref kref;
+#ifdef CONFIG_SRCU
+	struct rcu_head rcu_head;
+#endif
+	bool supplier_preactivated; /* Owned by consumer probe. */
+};
+
 static inline struct device *kobj_to_dev(struct kobject *kobj)
 {
 	return container_of(kobj, struct device, kobj);
-- 
2.27.0.rc0.183.gde8f92d652-goog

[PATCH v3 2/3] driver core: Add state_synced sysfs file for devices that support it

[Saravana Kannan]

This can be used to check if a device supports sync_state() callbacks
and therefore keeps resources left on by the bootloader enabled till all
its consumers have probed.

This can also be used to check if sync_state() has been called for a
device or whether it is still trying to keep resources enabled because
they were left enabled by the bootloader and all its consumers haven't
probed yet.

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 .../ABI/testing/sysfs-devices-state_synced    | 24 +++++++++++++++++++
 drivers/base/dd.c                             | 22 +++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-state_synced

diff --git a/Documentation/ABI/testing/sysfs-devices-state_synced b/Documentation/ABI/testing/sysfs-devices-state_synced
new file mode 100644
index 000000000000..0c922d7d02fc
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-state_synced
@@ -0,0 +1,24 @@
+What:		/sys/devices/.../state_synced
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		The /sys/devices/.../state_synced attribute is only present for
+		devices whose bus types or driver provides the .sync_state()
+		callback. The number read from it (0 or 1) reflects the value
+		of the device's 'state_synced' field. A value of 0 means the
+		.sync_state() callback hasn't been called yet. A value of 1
+		means the .sync_state() callback has been called.
+
+		Generally, if a device has sync_state() support and has some of
+		the resources it provides enabled at the time the kernel starts
+		(Eg: enabled by hardware reset or bootloader or anything that
+		run before the kernel starts), then it'll keep those resources
+		enabled and in a state that's compatible with the state they
+		were in at the start of the kernel. The device will stop doing
+		this only when the sync_state() callback has been called --
+		which happens only when all its consumer devices are registered
+		and have probed successfully. Resources that were left disabled
+		at the time the kernel starts are not affected or limited in
+		any way by sync_state() callbacks.
+
+
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 9a1d940342ac..7c04b88daac3 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -463,6 +463,18 @@ static void driver_deferred_probe_add_trigger(struct device *dev,
 		driver_deferred_probe_trigger();
 }
 
+static ssize_t state_synced_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	bool val;
+
+	device_lock(dev);
+	val = dev->state_synced;
+	device_unlock(dev);
+	return sprintf(buf, "%u\n", val);
+}
+static DEVICE_ATTR_RO(state_synced);
+
 static int really_probe(struct device *dev, struct device_driver *drv)
 {
 	int ret = -EPROBE_DEFER;
@@ -536,9 +548,16 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 		goto dev_groups_failed;
 	}
 
+	if (dev_has_sync_state(dev) &&
+	    device_create_file(dev, &dev_attr_state_synced)) {
+		dev_err(dev, "state_synced sysfs add failed\n");
+		goto dev_sysfs_state_synced_failed;
+	}
+
 	if (test_remove) {
 		test_remove = false;
 
+		device_remove_file(dev, &dev_attr_state_synced);
 		device_remove_groups(dev, drv->dev_groups);
 
 		if (dev->bus->remove)
@@ -568,6 +587,8 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 		 drv->bus->name, __func__, dev_name(dev), drv->name);
 	goto done;
 
+dev_sysfs_state_synced_failed:
+	device_remove_groups(dev, drv->dev_groups);
 dev_groups_failed:
 	if (dev->bus->remove)
 		dev->bus->remove(dev);
@@ -1105,6 +1126,7 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 
 		pm_runtime_put_sync(dev);
 
+		device_remove_file(dev, &dev_attr_state_synced);
 		device_remove_groups(dev, drv->dev_groups);
 
 		if (dev->bus && dev->bus->remove)
-- 
2.27.0.rc0.183.gde8f92d652-goog

[PATCH v3 3/3] driver core: Add waiting_for_supplier sysfs file for devices

[Saravana Kannan]

This would be useful to check if a device is not probing because it's
waiting for a supplier to be added and then linked to before it can
probe.

To reduce sysfs clutter, this file is added only if it can ever be 1.
So, if fw_devlink is disabled or set to permissive, this file is not
added. Also, this file is removed once the device probes as it's no
longer relevant.

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 .../sysfs-devices-waiting_for_supplier        | 17 ++++++++++++
 drivers/base/core.c                           | 26 +++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-waiting_for_supplier

diff --git a/Documentation/ABI/testing/sysfs-devices-waiting_for_supplier b/Documentation/ABI/testing/sysfs-devices-waiting_for_supplier
new file mode 100644
index 000000000000..59d073d20db6
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-waiting_for_supplier
@@ -0,0 +1,17 @@
+What:		/sys/devices/.../waiting_for_supplier
+Date:		May 2020
+Contact:	Saravana Kannan <saravanak@google.com>
+Description:
+		The /sys/devices/.../waiting_for_supplier attribute is only
+		present when fw_devlink kernel command line option is enabled
+		and is set to something stricter than "permissive".  It is
+		removed once a device probes successfully (because the
+		information is no longer relevant). The number read from it (0
+		or 1) reflects whether the device is waiting for one or more
+		suppliers to be added and then linked to using device links
+		before the device can probe.
+
+		A value of 0 means the device is not waiting for any suppliers
+		to be added before it can probe.  A value of 1 means the device
+		is waiting for one or more suppliers to be added before it can
+		probe.
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 81c8ef088d3a..dfd4e94ef790 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1033,6 +1033,22 @@ static void device_link_drop_managed(struct device_link *link)
 	kref_put(&link->kref, __device_link_del);
 }
 
+static ssize_t waiting_for_supplier_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	bool val;
+
+	device_lock(dev);
+	mutex_lock(&wfs_lock);
+	val = !list_empty(&dev->links.needs_suppliers)
+	      && dev->links.need_for_probe;
+	mutex_unlock(&wfs_lock);
+	device_unlock(dev);
+	return sprintf(buf, "%u\n", val);
+}
+static DEVICE_ATTR_RO(waiting_for_supplier);
+
 /**
  * device_links_driver_bound - Update device links after probing its driver.
  * @dev: Device to update the links for.
@@ -1057,6 +1073,7 @@ void device_links_driver_bound(struct device *dev)
 	mutex_lock(&wfs_lock);
 	list_del_init(&dev->links.needs_suppliers);
 	mutex_unlock(&wfs_lock);
+	device_remove_file(dev, &dev_attr_waiting_for_supplier);
 
 	device_links_write_lock();
 
@@ -2126,8 +2143,16 @@ static int device_add_attrs(struct device *dev)
 			goto err_remove_dev_groups;
 	}
 
+	if (fw_devlink_flags && !fw_devlink_is_permissive()) {
+		error = device_create_file(dev, &dev_attr_waiting_for_supplier);
+		if (error)
+			goto err_remove_dev_online;
+	}
+
 	return 0;
 
+ err_remove_dev_online:
+	device_remove_file(dev, &dev_attr_online);
  err_remove_dev_groups:
 	device_remove_groups(dev, dev->groups);
  err_remove_type_groups:
@@ -2145,6 +2170,7 @@ static void device_remove_attrs(struct device *dev)
 	struct class *class = dev->class;
 	const struct device_type *type = dev->type;
 
+	device_remove_file(dev, &dev_attr_waiting_for_supplier);
 	device_remove_file(dev, &dev_attr_online);
 	device_remove_groups(dev, dev->groups);
 
-- 
2.27.0.rc0.183.gde8f92d652-goog

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Saravana Kannan]

On Thu, May 21, 2020 at 12:18 PM Saravana Kannan <saravanak@google.com> wrote:
>
> With fw_devlink and with sync_state() callback features, there's a lot
> of device/device link related information that's not available in sysfs.
>
> Exposing these details to user space can be very useful in understanding
> suspend/resume issues, runtime pm issues, probing issues, figuring out
> the modules that'd be needed for first stage init, etc. In fact, an
> earlier verion of this series was very helpful in debugging and
> validating the recent memory leak fix[1].
>
> This series is based on driver-core-next and [1] cherry-picked on top of
> it.
>
> [1] - https://lore.kernel.org/lkml/20200519063000.128819-1-saravanak@google.com/
>
> v1->v2:
> Patch 1/4
> - New patch
> Patch 2/4
> - Fixed the warnings I saw before that were related to incorrect
>   sysfs removal code when a device link is deleted.
> - Fixed error handling in device_link_add()
> - Split up flags into more meaningful files.
> - Added status file.
> Patch 3/4
> - Fixed error handling that Greg pointed out before.
> Patch 4/4
> - New patch
>
> v2->v3:
> - Dropped patch 1/4 from v2 since it was already picked up. So numbering
>   has shifted.
> Patch 1/3
> - Added documentation
>
> Saravana Kannan (3):
>   driver core: Expose device link details in sysfs
>   driver core: Add state_synced sysfs file for devices that support it
>   driver core: Add waiting_for_supplier sysfs file for devices
>
>  Documentation/ABI/testing/sysfs-class-devlink | 126 ++++++++++
>  .../ABI/testing/sysfs-devices-consumer        |   8 +
>  .../ABI/testing/sysfs-devices-state_synced    |  24 ++
>  .../ABI/testing/sysfs-devices-supplier        |   8 +
>  .../sysfs-devices-waiting_for_supplier        |  17 ++
>  drivers/base/core.c                           | 237 +++++++++++++++++-
>  drivers/base/dd.c                             |  22 ++
>  include/linux/device.h                        |  58 ++---
>  8 files changed, 464 insertions(+), 36 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-devlink
>  create mode 100644 Documentation/ABI/testing/sysfs-devices-consumer
>  create mode 100644 Documentation/ABI/testing/sysfs-devices-state_synced
>  create mode 100644 Documentation/ABI/testing/sysfs-devices-supplier
>  create mode 100644 Documentation/ABI/testing/sysfs-devices-waiting_for_supplier

Friendly reminder.

-Saravana

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Greg Kroah-Hartman]

On Thu, May 28, 2020 at 02:18:23PM -0700, Saravana Kannan wrote:
> On Thu, May 21, 2020 at 12:18 PM Saravana Kannan <saravanak@google.com> wrote:
> >
> > With fw_devlink and with sync_state() callback features, there's a lot
> > of device/device link related information that's not available in sysfs.
> >
> > Exposing these details to user space can be very useful in understanding
> > suspend/resume issues, runtime pm issues, probing issues, figuring out
> > the modules that'd be needed for first stage init, etc. In fact, an
> > earlier verion of this series was very helpful in debugging and
> > validating the recent memory leak fix[1].
> >
> > This series is based on driver-core-next and [1] cherry-picked on top of
> > it.
> >
> > [1] - https://lore.kernel.org/lkml/20200519063000.128819-1-saravanak@google.com/
> >
> > v1->v2:
> > Patch 1/4
> > - New patch
> > Patch 2/4
> > - Fixed the warnings I saw before that were related to incorrect
> >   sysfs removal code when a device link is deleted.
> > - Fixed error handling in device_link_add()
> > - Split up flags into more meaningful files.
> > - Added status file.
> > Patch 3/4
> > - Fixed error handling that Greg pointed out before.
> > Patch 4/4
> > - New patch
> >
> > v2->v3:
> > - Dropped patch 1/4 from v2 since it was already picked up. So numbering
> >   has shifted.
> > Patch 1/3
> > - Added documentation
> >
> > Saravana Kannan (3):
> >   driver core: Expose device link details in sysfs
> >   driver core: Add state_synced sysfs file for devices that support it
> >   driver core: Add waiting_for_supplier sysfs file for devices
> >
> >  Documentation/ABI/testing/sysfs-class-devlink | 126 ++++++++++
> >  .../ABI/testing/sysfs-devices-consumer        |   8 +
> >  .../ABI/testing/sysfs-devices-state_synced    |  24 ++
> >  .../ABI/testing/sysfs-devices-supplier        |   8 +
> >  .../sysfs-devices-waiting_for_supplier        |  17 ++
> >  drivers/base/core.c                           | 237 +++++++++++++++++-
> >  drivers/base/dd.c                             |  22 ++
> >  include/linux/device.h                        |  58 ++---
> >  8 files changed, 464 insertions(+), 36 deletions(-)
> >  create mode 100644 Documentation/ABI/testing/sysfs-class-devlink
> >  create mode 100644 Documentation/ABI/testing/sysfs-devices-consumer
> >  create mode 100644 Documentation/ABI/testing/sysfs-devices-state_synced
> >  create mode 100644 Documentation/ABI/testing/sysfs-devices-supplier
> >  create mode 100644 Documentation/ABI/testing/sysfs-devices-waiting_for_supplier
> 
> Friendly reminder.

Looks semi-sane, but it's too close to the merge window at the moment
for me to take this.  If there's no objections by the time 5.8-rc1 is
out, I'll queue it up in my tree for 5.9-rc1.

thanks,

greg k-h

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Saravana Kannan]

On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> Looks semi-sane, but it's too close to the merge window at the moment
> for me to take this.  If there's no objections by the time 5.8-rc1 is
> out, I'll queue it up in my tree for 5.9-rc1.

Another friendly reminder :)

-Saravana

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Saravana Kannan]

On Tue, Jun 16, 2020 at 8:45 PM Saravana Kannan <saravanak@google.com> wrote:
>
> On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > Looks semi-sane, but it's too close to the merge window at the moment
> > for me to take this.  If there's no objections by the time 5.8-rc1 is
> > out, I'll queue it up in my tree for 5.9-rc1.
>
> Another friendly reminder :)

*nudge* *nudge*

-Saravana

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Greg Kroah-Hartman]

On Mon, Jul 06, 2020 at 03:45:02PM -0700, Saravana Kannan wrote:
> On Tue, Jun 16, 2020 at 8:45 PM Saravana Kannan <saravanak@google.com> wrote:
> >
> > On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > > Looks semi-sane, but it's too close to the merge window at the moment
> > > for me to take this.  If there's no objections by the time 5.8-rc1 is
> > > out, I'll queue it up in my tree for 5.9-rc1.
> >
> > Another friendly reminder :)
> 
> *nudge* *nudge*

Looks sane, given no objections, let's see what linux-next thinks about
it...

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Saravana Kannan]

On Fri, Jul 10, 2020 at 6:23 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Mon, Jul 06, 2020 at 03:45:02PM -0700, Saravana Kannan wrote:
> > On Tue, Jun 16, 2020 at 8:45 PM Saravana Kannan <saravanak@google.com> wrote:
> > >
> > > On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> wrote:
> > > > Looks semi-sane, but it's too close to the merge window at the moment
> > > > for me to take this.  If there's no objections by the time 5.8-rc1 is
> > > > out, I'll queue it up in my tree for 5.9-rc1.
> > >
> > > Another friendly reminder :)
> >
> > *nudge* *nudge*
>
> Looks sane, given no objections, let's see what linux-next thinks about
> it...

Thanks!

-Saravana

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Marek Szyprowski]

Hi Greg and Saravana,

On 10.07.2020 15:23, Greg Kroah-Hartman wrote:
> On Mon, Jul 06, 2020 at 03:45:02PM -0700, Saravana Kannan wrote:
>> On Tue, Jun 16, 2020 at 8:45 PM Saravana Kannan <saravanak@google.com> wrote:
>>> On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
>>> <gregkh@linuxfoundation.org> wrote:
>>>> Looks semi-sane, but it's too close to the merge window at the moment
>>>> for me to take this.  If there's no objections by the time 5.8-rc1 is
>>>> out, I'll queue it up in my tree for 5.9-rc1.
>>> Another friendly reminder :)
>> *nudge* *nudge*
> Looks sane, given no objections, let's see what linux-next thinks about
> it...

linux-next is not very happy from this patchset... Starting from 
next-20200713 I see a few new issues on various Samsung Exynos based 
boards. Here are examples from Exynos4412-based Odroid U3 board (ARM 
32bit, kernel compiled from exynos_defconfig):

BUG: sleeping function called from invalid context at 
kernel/locking/mutex.c:935
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 12, name: kworker/0:1
2 locks held by kworker/0:1/12:
  #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: 
process_one_work+0x174/0x7dc
  #1: ee921f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at: 
process_one_work+0x174/0x7dc
Preemption disabled at:
[<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W 
5.8.0-rc3-00022-g287905e68dd2 #8753
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: rcu_gp srcu_invoke_callbacks
[<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
[<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
[<c0517f04>] (dump_stack) from [<c0159188>] (___might_sleep+0x288/0x2d8)
[<c0159188>] (___might_sleep) from [<c0abbd1c>] (__mutex_lock+0x48/0xb18)
[<c0abbd1c>] (__mutex_lock) from [<c0abc808>] (mutex_lock_nested+0x1c/0x24)
[<c0abc808>] (mutex_lock_nested) from [<c064590c>] (device_del+0x30/0x39c)
[<c064590c>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
[<c0645c9c>] (device_unregister) from [<c01b10fc>] 
(srcu_invoke_callbacks+0xcc/0x154)
[<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>] 
(process_one_work+0x234/0x7dc)
[<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
[<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
[<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
Exception stack(0xee921fb0 to 0xee921ff8)


BUG: scheduling while atomic: kworker/0:0/5/0x00000201
3 locks held by kworker/0:0/5:
  #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: 
process_one_work+0x174/0x7dc
  #1: ee907f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at: 
process_one_work+0x174/0x7dc
  #2: c11367e4 (kernfs_mutex){+.+.}-{3:3}, at: 
kernfs_remove_by_name_ns+0x24/0x94
Modules linked in:
Preemption disabled at:
[<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G        W 
5.8.0-rc3-00022-g287905e68dd2 #8753
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: rcu_gp srcu_invoke_callbacks
[<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
[<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
[<c0517f04>] (dump_stack) from [<c0158da0>] (__schedule_bug+0x88/0xe0)
[<c0158da0>] (__schedule_bug) from [<c0ab7f88>] (__schedule+0x5d0/0x83c)
[<c0ab7f88>] (__schedule) from [<c0ab8258>] (schedule+0x64/0x124)
[<c0ab8258>] (schedule) from [<c0ab8768>] 
(schedule_preempt_disabled+0x14/0x20)
[<c0ab8768>] (schedule_preempt_disabled) from [<c0abc1ec>] 
(__mutex_lock+0x518/0xb18)
[<c0abc1ec>] (__mutex_lock) from [<c0abc808>] (mutex_lock_nested+0x1c/0x24)
[<c0abc808>] (mutex_lock_nested) from [<c0362fc0>] 
(kernfs_remove_by_name_ns+0x24/0x94)
[<c0362fc0>] (kernfs_remove_by_name_ns) from [<c0644eac>] 
(device_remove_class_symlinks+0x70/0x94)
[<c0644eac>] (device_remove_class_symlinks) from [<c0645994>] 
(device_del+0xb8/0x39c)
[<c0645994>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
[<c0645c9c>] (device_unregister) from [<c01b10fc>] 
(srcu_invoke_callbacks+0xcc/0x154)
[<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>] 
(process_one_work+0x234/0x7dc)
[<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
[<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
[<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
Exception stack(0xee907fb0 to 0xee907ff8)
sysfs: cannot create duplicate filename 
'/devices/virtual/devlink/regulator.28:cpu0'

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5 at kernel/sched/core.c:3897 
preempt_count_sub+0x104/0x108
DEBUG_LOCKS_WARN_ON(val > preempt_count())
Modules linked in:
CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G        W 
5.8.0-rc3-00022-g287905e68dd2 #8753
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: rcu_gp srcu_invoke_callbacks
[<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
[<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
[<c0517f04>] (dump_stack) from [<c01270a8>] (__warn+0xf0/0x108)
[<c01270a8>] (__warn) from [<c0127134>] (warn_slowpath_fmt+0x74/0xb8)
[<c0127134>] (warn_slowpath_fmt) from [<c0158efc>] 
(preempt_count_sub+0x104/0x108)
[<c0158efc>] (preempt_count_sub) from [<c012fee4>] 
(__local_bh_enable_ip+0x74/0x16c)
[<c012fee4>] (__local_bh_enable_ip) from [<c01b1108>] 
(srcu_invoke_callbacks+0xd8/0x154)
[<c01b1108>] (srcu_invoke_callbacks) from [<c01493c4>] 
(process_one_work+0x234/0x7dc)
[<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
[<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
[<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
Exception stack(0xee907fb0 to 0xee907ff8)
7fa0:                                     00000000 00000000 00000000 
00000000
7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
7fe0: 00000000 00000000 00000000 00000000 00000013 00000000
irq event stamp: 2274
hardirqs last  enabled at (2273): [<c02b3274>] __slab_free+0x2b0/0x480
hardirqs last disabled at (2274): [<c012fecc>] 
__local_bh_enable_ip+0x5c/0x16c
softirqs last  enabled at (2184): [<c010174c>] __do_softirq+0x50c/0x608
softirqs last disabled at (2056): [<c01b10e4>] 
srcu_invoke_callbacks+0xb4/0x154
---[ end trace eaa99e7b5e453175 ]---

PU: 0 PID: 1 Comm: swapper/0 Tainted: G        W 
5.8.0-rc3-00022-g287905e68dd2 #8753
Hardware name: Samsung Exynos (Flattened Device Tree)
[<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
[<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
[<c0517f04>] (dump_stack) from [<c0365474>] (sysfs_warn_dup+0x58/0x64)
[<c0365474>] (sysfs_warn_dup) from [<c03655a8>] 
(sysfs_create_dir_ns+0xe0/0xf4)
[<c03655a8>] (sysfs_create_dir_ns) from [<c051f218>] 
(kobject_add_internal+0xb8/0x370)
[<c051f218>] (kobject_add_internal) from [<c051f69c>] 
(kobject_add+0x5c/0xbc)
[<c051f69c>] (kobject_add) from [<c0647338>] (device_add+0x100/0x744)
[<c0647338>] (device_add) from [<c0647b88>] (device_link_add+0x1f4/0x5d0)
[<c0647b88>] (device_link_add) from [<c0582f60>] (_regulator_get+0xf4/0x280)
[<c0582f60>] (_regulator_get) from [<c0803da4>] 
(dev_pm_opp_set_regulators+0xf8/0x210)
[<c0803da4>] (dev_pm_opp_set_regulators) from [<c080df80>] 
(cpufreq_init+0xb8/0x304)
[<c080df80>] (cpufreq_init) from [<c080aae0>] (cpufreq_online+0x2c8/0x9f8)
[<c080aae0>] (cpufreq_online) from [<c080b2ac>] (cpufreq_add_dev+0x8c/0xc0)
[<c080b2ac>] (cpufreq_add_dev) from [<c0649854>] 
(subsys_interface_register+0xa8/0xf4)
[<c0649854>] (subsys_interface_register) from [<c0808184>] 
(cpufreq_register_driver+0x178/0x294)
[<c0808184>] (cpufreq_register_driver) from [<c080ddac>] 
(dt_cpufreq_probe+0xd8/0x1f4)
[<c080ddac>] (dt_cpufreq_probe) from [<c064e048>] 
(platform_drv_probe+0x6c/0xa4)
[<c064e048>] (platform_drv_probe) from [<c064b664>] 
(really_probe+0x200/0x48c)
[<c064b664>] (really_probe) from [<c064ba58>] 
(driver_probe_device+0x78/0x1fc)
[<c064ba58>] (driver_probe_device) from [<c064be40>] 
(device_driver_attach+0x58/0x60)
[<c064be40>] (device_driver_attach) from [<c064bf24>] 
(__driver_attach+0xdc/0x174)
[<c064bf24>] (__driver_attach) from [<c0649470>] 
(bus_for_each_dev+0x68/0xb4)
[<c0649470>] (bus_for_each_dev) from [<c064a7a4>] 
(bus_add_driver+0x158/0x214)
[<c064a7a4>] (bus_add_driver) from [<c064cdf8>] (driver_register+0x78/0x110)
[<c064cdf8>] (driver_register) from [<c0102378>] 
(do_one_initcall+0x8c/0x424)
[<c0102378>] (do_one_initcall) from [<c1001158>] 
(kernel_init_freeable+0x190/0x204)
[<c1001158>] (kernel_init_freeable) from [<c0ab7104>] 
(kernel_init+0x8/0x118)
[<c0ab7104>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20)
Exception stack(0xee8f1fb0 to 0xee8f1ff8)
...
BUG: sleeping function called from invalid context at 
kernel/locking/mutex.c:935
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5, name: kworker/0:0
INFO: lockdep is turned off.
Preemption disabled at:
[<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G        W 
5.8.0-rc3-00022-g287905e68dd2 #8753
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: rcu_gp srcu_invoke_callbacks
[<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
[<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
[<c0517f04>] (dump_stack) from [<c0159188>] (___might_sleep+0x288/0x2d8)
[<c0159188>] (___might_sleep) from [<c0abbd1c>] (__mutex_lock+0x48/0xb18)
[<c0abbd1c>] (__mutex_lock) from [<c0abc808>] (mutex_lock_nested+0x1c/0x24)
[<c0abc808>] (mutex_lock_nested) from [<c064590c>] (device_del+0x30/0x39c)
[<c064590c>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
[<c0645c9c>] (device_unregister) from [<c01b10fc>] 
(srcu_invoke_callbacks+0xcc/0x154)
[<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>] 
(process_one_work+0x234/0x7dc)
[<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
[<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
[<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
Exception stack(0xee907fb0 to 0xee907ff8)
...
kobject_add_internal failed for regulator.28:cpu0 with -EEXIST, don't 
try to register things with the same name in the same directory.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Saravana Kannan]

On Wed, Jul 15, 2020 at 1:22 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
>
> Hi Greg and Saravana,
>
> On 10.07.2020 15:23, Greg Kroah-Hartman wrote:
> > On Mon, Jul 06, 2020 at 03:45:02PM -0700, Saravana Kannan wrote:
> >> On Tue, Jun 16, 2020 at 8:45 PM Saravana Kannan <saravanak@google.com> wrote:
> >>> On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
> >>> <gregkh@linuxfoundation.org> wrote:
> >>>> Looks semi-sane, but it's too close to the merge window at the moment
> >>>> for me to take this.  If there's no objections by the time 5.8-rc1 is
> >>>> out, I'll queue it up in my tree for 5.9-rc1.
> >>> Another friendly reminder :)
> >> *nudge* *nudge*
> > Looks sane, given no objections, let's see what linux-next thinks about
> > it...
>
> linux-next is not very happy from this patchset... Starting from
> next-20200713 I see a few new issues on various Samsung Exynos based
> boards. Here are examples from Exynos4412-based Odroid U3 board (ARM
> 32bit, kernel compiled from exynos_defconfig):

Thanks for the bug reports.

> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:935
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 12, name: kworker/0:1
> 2 locks held by kworker/0:1/12:
>   #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
> process_one_work+0x174/0x7dc
>   #1: ee921f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at:
> process_one_work+0x174/0x7dc
> Preemption disabled at:
> [<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154

Sigh... probably some SRCU screw up when the device link is deleted.
I'll look at it by the end of this week. If you don't mind, what SRCU
debug config caught this for you? That way, I can reproduce it on my
end.

-Saravana

> CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W
> 5.8.0-rc3-00022-g287905e68dd2 #8753
> Hardware name: Samsung Exynos (Flattened Device Tree)
> Workqueue: rcu_gp srcu_invoke_callbacks
> [<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
> [<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
> [<c0517f04>] (dump_stack) from [<c0159188>] (___might_sleep+0x288/0x2d8)
> [<c0159188>] (___might_sleep) from [<c0abbd1c>] (__mutex_lock+0x48/0xb18)
> [<c0abbd1c>] (__mutex_lock) from [<c0abc808>] (mutex_lock_nested+0x1c/0x24)
> [<c0abc808>] (mutex_lock_nested) from [<c064590c>] (device_del+0x30/0x39c)
> [<c064590c>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
> [<c0645c9c>] (device_unregister) from [<c01b10fc>]
> (srcu_invoke_callbacks+0xcc/0x154)
> [<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>]
> (process_one_work+0x234/0x7dc)
> [<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
> [<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
> [<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee921fb0 to 0xee921ff8)
>
>
> BUG: scheduling while atomic: kworker/0:0/5/0x00000201
> 3 locks held by kworker/0:0/5:
>   #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
> process_one_work+0x174/0x7dc
>   #1: ee907f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at:
> process_one_work+0x174/0x7dc
>   #2: c11367e4 (kernfs_mutex){+.+.}-{3:3}, at:
> kernfs_remove_by_name_ns+0x24/0x94
> Modules linked in:
> Preemption disabled at:
> [<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
> CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G        W
> 5.8.0-rc3-00022-g287905e68dd2 #8753
> Hardware name: Samsung Exynos (Flattened Device Tree)
> Workqueue: rcu_gp srcu_invoke_callbacks
> [<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
> [<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
> [<c0517f04>] (dump_stack) from [<c0158da0>] (__schedule_bug+0x88/0xe0)
> [<c0158da0>] (__schedule_bug) from [<c0ab7f88>] (__schedule+0x5d0/0x83c)
> [<c0ab7f88>] (__schedule) from [<c0ab8258>] (schedule+0x64/0x124)
> [<c0ab8258>] (schedule) from [<c0ab8768>]
> (schedule_preempt_disabled+0x14/0x20)
> [<c0ab8768>] (schedule_preempt_disabled) from [<c0abc1ec>]
> (__mutex_lock+0x518/0xb18)
> [<c0abc1ec>] (__mutex_lock) from [<c0abc808>] (mutex_lock_nested+0x1c/0x24)
> [<c0abc808>] (mutex_lock_nested) from [<c0362fc0>]
> (kernfs_remove_by_name_ns+0x24/0x94)
> [<c0362fc0>] (kernfs_remove_by_name_ns) from [<c0644eac>]
> (device_remove_class_symlinks+0x70/0x94)
> [<c0644eac>] (device_remove_class_symlinks) from [<c0645994>]
> (device_del+0xb8/0x39c)
> [<c0645994>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
> [<c0645c9c>] (device_unregister) from [<c01b10fc>]
> (srcu_invoke_callbacks+0xcc/0x154)
> [<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>]
> (process_one_work+0x234/0x7dc)
> [<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
> [<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
> [<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee907fb0 to 0xee907ff8)
> sysfs: cannot create duplicate filename
> '/devices/virtual/devlink/regulator.28:cpu0'
>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 5 at kernel/sched/core.c:3897
> preempt_count_sub+0x104/0x108
> DEBUG_LOCKS_WARN_ON(val > preempt_count())
> Modules linked in:
> CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G        W
> 5.8.0-rc3-00022-g287905e68dd2 #8753
> Hardware name: Samsung Exynos (Flattened Device Tree)
> Workqueue: rcu_gp srcu_invoke_callbacks
> [<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
> [<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
> [<c0517f04>] (dump_stack) from [<c01270a8>] (__warn+0xf0/0x108)
> [<c01270a8>] (__warn) from [<c0127134>] (warn_slowpath_fmt+0x74/0xb8)
> [<c0127134>] (warn_slowpath_fmt) from [<c0158efc>]
> (preempt_count_sub+0x104/0x108)
> [<c0158efc>] (preempt_count_sub) from [<c012fee4>]
> (__local_bh_enable_ip+0x74/0x16c)
> [<c012fee4>] (__local_bh_enable_ip) from [<c01b1108>]
> (srcu_invoke_callbacks+0xd8/0x154)
> [<c01b1108>] (srcu_invoke_callbacks) from [<c01493c4>]
> (process_one_work+0x234/0x7dc)
> [<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
> [<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
> [<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee907fb0 to 0xee907ff8)
> 7fa0:                                     00000000 00000000 00000000
> 00000000
> 7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000
> 7fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> irq event stamp: 2274
> hardirqs last  enabled at (2273): [<c02b3274>] __slab_free+0x2b0/0x480
> hardirqs last disabled at (2274): [<c012fecc>]
> __local_bh_enable_ip+0x5c/0x16c
> softirqs last  enabled at (2184): [<c010174c>] __do_softirq+0x50c/0x608
> softirqs last disabled at (2056): [<c01b10e4>]
> srcu_invoke_callbacks+0xb4/0x154
> ---[ end trace eaa99e7b5e453175 ]---
>
> PU: 0 PID: 1 Comm: swapper/0 Tainted: G        W
> 5.8.0-rc3-00022-g287905e68dd2 #8753
> Hardware name: Samsung Exynos (Flattened Device Tree)
> [<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
> [<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
> [<c0517f04>] (dump_stack) from [<c0365474>] (sysfs_warn_dup+0x58/0x64)
> [<c0365474>] (sysfs_warn_dup) from [<c03655a8>]
> (sysfs_create_dir_ns+0xe0/0xf4)
> [<c03655a8>] (sysfs_create_dir_ns) from [<c051f218>]
> (kobject_add_internal+0xb8/0x370)
> [<c051f218>] (kobject_add_internal) from [<c051f69c>]
> (kobject_add+0x5c/0xbc)
> [<c051f69c>] (kobject_add) from [<c0647338>] (device_add+0x100/0x744)
> [<c0647338>] (device_add) from [<c0647b88>] (device_link_add+0x1f4/0x5d0)
> [<c0647b88>] (device_link_add) from [<c0582f60>] (_regulator_get+0xf4/0x280)
> [<c0582f60>] (_regulator_get) from [<c0803da4>]
> (dev_pm_opp_set_regulators+0xf8/0x210)
> [<c0803da4>] (dev_pm_opp_set_regulators) from [<c080df80>]
> (cpufreq_init+0xb8/0x304)
> [<c080df80>] (cpufreq_init) from [<c080aae0>] (cpufreq_online+0x2c8/0x9f8)
> [<c080aae0>] (cpufreq_online) from [<c080b2ac>] (cpufreq_add_dev+0x8c/0xc0)
> [<c080b2ac>] (cpufreq_add_dev) from [<c0649854>]
> (subsys_interface_register+0xa8/0xf4)
> [<c0649854>] (subsys_interface_register) from [<c0808184>]
> (cpufreq_register_driver+0x178/0x294)
> [<c0808184>] (cpufreq_register_driver) from [<c080ddac>]
> (dt_cpufreq_probe+0xd8/0x1f4)
> [<c080ddac>] (dt_cpufreq_probe) from [<c064e048>]
> (platform_drv_probe+0x6c/0xa4)
> [<c064e048>] (platform_drv_probe) from [<c064b664>]
> (really_probe+0x200/0x48c)
> [<c064b664>] (really_probe) from [<c064ba58>]
> (driver_probe_device+0x78/0x1fc)
> [<c064ba58>] (driver_probe_device) from [<c064be40>]
> (device_driver_attach+0x58/0x60)
> [<c064be40>] (device_driver_attach) from [<c064bf24>]
> (__driver_attach+0xdc/0x174)
> [<c064bf24>] (__driver_attach) from [<c0649470>]
> (bus_for_each_dev+0x68/0xb4)
> [<c0649470>] (bus_for_each_dev) from [<c064a7a4>]
> (bus_add_driver+0x158/0x214)
> [<c064a7a4>] (bus_add_driver) from [<c064cdf8>] (driver_register+0x78/0x110)
> [<c064cdf8>] (driver_register) from [<c0102378>]
> (do_one_initcall+0x8c/0x424)
> [<c0102378>] (do_one_initcall) from [<c1001158>]
> (kernel_init_freeable+0x190/0x204)
> [<c1001158>] (kernel_init_freeable) from [<c0ab7104>]
> (kernel_init+0x8/0x118)
> [<c0ab7104>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee8f1fb0 to 0xee8f1ff8)
> ...
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:935
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5, name: kworker/0:0
> INFO: lockdep is turned off.
> Preemption disabled at:
> [<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
> CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G        W
> 5.8.0-rc3-00022-g287905e68dd2 #8753
> Hardware name: Samsung Exynos (Flattened Device Tree)
> Workqueue: rcu_gp srcu_invoke_callbacks
> [<c011184c>] (unwind_backtrace) from [<c010d250>] (show_stack+0x10/0x14)
> [<c010d250>] (show_stack) from [<c0517f04>] (dump_stack+0xbc/0xe8)
> [<c0517f04>] (dump_stack) from [<c0159188>] (___might_sleep+0x288/0x2d8)
> [<c0159188>] (___might_sleep) from [<c0abbd1c>] (__mutex_lock+0x48/0xb18)
> [<c0abbd1c>] (__mutex_lock) from [<c0abc808>] (mutex_lock_nested+0x1c/0x24)
> [<c0abc808>] (mutex_lock_nested) from [<c064590c>] (device_del+0x30/0x39c)
> [<c064590c>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
> [<c0645c9c>] (device_unregister) from [<c01b10fc>]
> (srcu_invoke_callbacks+0xcc/0x154)
> [<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>]
> (process_one_work+0x234/0x7dc)
> [<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
> [<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
> [<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee907fb0 to 0xee907ff8)
> ...
> kobject_add_internal failed for regulator.28:cpu0 with -EEXIST, don't
> try to register things with the same name in the same directory.
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>

Re: [PATCH v3 0/3] driver core: Add device link related sysfs files

[Marek Szyprowski]

Hi Saravana,

On 15.07.2020 10:53, Saravana Kannan wrote:
> On Wed, Jul 15, 2020 at 1:22 AM Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
>> On 10.07.2020 15:23, Greg Kroah-Hartman wrote:
>>> On Mon, Jul 06, 2020 at 03:45:02PM -0700, Saravana Kannan wrote:
>>>> On Tue, Jun 16, 2020 at 8:45 PM Saravana Kannan <saravanak@google.com> wrote:
>>>>> On Fri, May 29, 2020 at 5:30 AM Greg Kroah-Hartman
>>>>> <gregkh@linuxfoundation.org> wrote:
>>>>>> Looks semi-sane, but it's too close to the merge window at the moment
>>>>>> for me to take this.  If there's no objections by the time 5.8-rc1 is
>>>>>> out, I'll queue it up in my tree for 5.9-rc1.
>>>>> Another friendly reminder :)
>>>> *nudge* *nudge*
>>> Looks sane, given no objections, let's see what linux-next thinks about
>>> it...
>> linux-next is not very happy from this patchset... Starting from
>> next-20200713 I see a few new issues on various Samsung Exynos based
>> boards. Here are examples from Exynos4412-based Odroid U3 board (ARM
>> 32bit, kernel compiled from exynos_defconfig):
> Thanks for the bug reports.
>
>> BUG: sleeping function called from invalid context at
>> kernel/locking/mutex.c:935
>> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 12, name: kworker/0:1
>> 2 locks held by kworker/0:1/12:
>>    #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
>> process_one_work+0x174/0x7dc
>>    #1: ee921f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at:
>> process_one_work+0x174/0x7dc
>> Preemption disabled at:
>> [<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
> Sigh... probably some SRCU screw up when the device link is deleted.
> I'll look at it by the end of this week. If you don't mind, what SRCU
> debug config caught this for you? That way, I can reproduce it on my
> end.

Just the options enabled in the default exynos_defconfig in current 
linux-next. I didn't check any particular options yet.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v3 1/3] driver core: Expose device link details in sysfs

[Guenter Roeck]

Hi,

On Thu, May 21, 2020 at 12:17:58PM -0700, Saravana Kannan wrote:
> It's helpful to be able to look at device link details from sysfs. So,
> expose it in sysfs.
> 
> Say device-A is supplier of device-B. These are the additional files
> this patch would create:
> 
> /sys/class/devlink/device-A:device-B/
> 	auto_remove_on
> 	consumer/ -> .../device-B/
> 	runtime_pm
> 	status
> 	supplier/ -> .../device-A/
> 	sync_state_only
> 
> /sys/devices/.../device-A/
> 	consumer:device-B/ -> /sys/class/devlink/device-A:device-B/
> 
> /sys/devices/.../device-B/
> 	supplier:device-A/ -> /sys/class/devlink/device-A:device-B/
> 
> That way:
> To get a list of all the device link in the system:
> ls /sys/class/devlink/
> 
> To get the consumer names and links of a device:
> ls -d /sys/devices/.../device-X/consumer:*
> 
> To get the supplier names and links of a device:
> ls -d /sys/devices/.../device-X/supplier:*
> 
> Signed-off-by: Saravana Kannan <saravanak@google.com>

This patch creates a lot of noise in linux-next when booting various
qemu images. Example log output as well as bisect results below.
Reverting the patch fixes the problem.

Guenter

---
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:935
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 13, name: kworker/0:1
2 locks held by kworker/0:1/13:
 #0: c78048a4 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x1a0/0x728
 #1: c78ebf18 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at: process_one_work+0x1a0/0x728
Preemption disabled at:
[<c0085bb4>] srcu_invoke_callbacks+0xc0/0x158
CPU: 0 PID: 13 Comm: kworker/0:1 Not tainted 5.8.0-rc5-next-20200715 #1
Hardware name: Freescale i.MX25 (Device Tree Support)
Workqueue: rcu_gp srcu_invoke_callbacks
[<c0010fe4>] (unwind_backtrace) from [<c000e740>] (show_stack+0x10/0x18)
[<c000e740>] (show_stack) from [<c050985c>] (dump_stack+0x20/0x2c)
[<c050985c>] (dump_stack) from [<c00496e4>] (___might_sleep+0x1d0/0x2cc)
[<c00496e4>] (___might_sleep) from [<c09105e8>] (__mutex_lock+0x38/0x654)
[<c09105e8>] (__mutex_lock) from [<c0910c20>] (mutex_lock_nested+0x1c/0x28)
[<c0910c20>] (mutex_lock_nested) from [<c05b25dc>] (device_del+0x2c/0x3f0)
[<c05b25dc>] (device_del) from [<c05b2a10>] (__device_link_free_srcu+0x50/0x64)
[<c05b2a10>] (__device_link_free_srcu) from [<c0085bc4>] (srcu_invoke_callbacks+0xd0/0x158)
[<c0085bc4>] (srcu_invoke_callbacks) from [<c003ad2c>] (process_one_work+0x284/0x728)
[<c003ad2c>] (process_one_work) from [<c003b1fc>] (worker_thread+0x2c/0x52c)
[<c003b1fc>] (worker_thread) from [<c0042df8>] (kthread+0x154/0x180)
[<c0042df8>] (kthread) from [<c0008530>] (ret_from_fork+0x14/0x24)
Exception stack(0xc78ebfb0 to 0xc78ebff8)
bfa0:                                     00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
BUG: scheduling while atomic: kworker/0:1/13/0x00000201
3 locks held by kworker/0:1/13:
 #0: c78048a4 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x1a0/0x728
 #1: c78ebf18 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at: process_one_work+0x1a0/0x728
 #2: c0cf5710 (gdp_mutex){+.+.}-{3:3}, at: cleanup_glue_dir.part.14+0x14/0xa0
Modules linked in:
Preemption disabled at:
[<c0085bb4>] srcu_invoke_callbacks+0xc0/0x158
CPU: 0 PID: 13 Comm: kworker/0:1 Tainted: G        W         5.8.0-rc5-next-20200715 #1
Hardware name: Freescale i.MX25 (Device Tree Support)
Workqueue: rcu_gp srcu_invoke_callbacks
[<c0010fe4>] (unwind_backtrace) from [<c000e740>] (show_stack+0x10/0x18)
[<c000e740>] (show_stack) from [<c050985c>] (dump_stack+0x20/0x2c)
[<c050985c>] (dump_stack) from [<c0049910>] (__schedule_bug+0x88/0xf0)
[<c0049910>] (__schedule_bug) from [<c090e148>] (__schedule+0x5f0/0x824)
[<c090e148>] (__schedule) from [<c090e3d0>] (schedule+0x54/0x128)
[<c090e3d0>] (schedule) from [<c090e838>] (schedule_preempt_disabled+0x14/0x28)
[<c090e838>] (schedule_preempt_disabled) from [<c0910744>] (__mutex_lock+0x194/0x654)
[<c0910744>] (__mutex_lock) from [<c0910c20>] (mutex_lock_nested+0x1c/0x28)
[<c0910c20>] (mutex_lock_nested) from [<c05b1d5c>] (cleanup_glue_dir.part.14+0x14/0xa0)
[<c05b1d5c>] (cleanup_glue_dir.part.14) from [<c05b296c>] (device_del+0x3bc/0x3f0)
[<c05b296c>] (device_del) from [<c05b2a10>] (__device_link_free_srcu+0x50/0x64)
[<c05b2a10>] (__device_link_free_srcu) from [<c0085bc4>] (srcu_invoke_callbacks+0xd0/0x158)
[<c0085bc4>] (srcu_invoke_callbacks) from [<c003ad2c>] (process_one_work+0x284/0x728)
[<c003ad2c>] (process_one_work) from [<c003b1fc>] (worker_thread+0x2c/0x52c)
[<c003b1fc>] (worker_thread) from [<c0042df8>] (kthread+0x154/0x180)
[<c0042df8>] (kthread) from [<c0008530>] (ret_from_fork+0x14/0x24)
Exception stack(0xc78ebfb0 to 0xc78ebff8)
bfa0:                                     00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
------------[ cut here ]------------

---
# bad: [ca0e494af5edb59002665bf12871e94b4163a257] Add linux-next specific files for 20200715
# good: [11ba468877bb23f28956a35e896356252d63c983] Linux 5.8-rc5
git bisect start 'HEAD' 'v5.8-rc5'
# good: [8a21074e4724ce86b4e1a8fdc271081a86303014] Merge remote-tracking branch 'crypto/master'
git bisect good 8a21074e4724ce86b4e1a8fdc271081a86303014
# good: [71f459b5cd96681f615e5c920b3a38ab89e8b5f1] Merge remote-tracking branch 'audit/next'
git bisect good 71f459b5cd96681f615e5c920b3a38ab89e8b5f1
# bad: [5a310f73f874211ee7aa570b308d50def85aff1c] Merge remote-tracking branch 'thunderbolt/next'
git bisect bad 5a310f73f874211ee7aa570b308d50def85aff1c
# good: [db01f1b1e840f46bdd64c6c846e7b3246bdff55a] Merge remote-tracking branch 'kvm/linux-next'
git bisect good db01f1b1e840f46bdd64c6c846e7b3246bdff55a
# bad: [89947fbc4b34bfdef7ade2b26274e78b32d4e39f] Merge remote-tracking branch 'usb/usb-next'
git bisect bad 89947fbc4b34bfdef7ade2b26274e78b32d4e39f
# bad: [c845fc08689b52c05c0201614ac89f7978caa169] Merge remote-tracking branch 'driver-core/driver-core-next'
git bisect bad c845fc08689b52c05c0201614ac89f7978caa169
# good: [4621ddca720ceb9b45725acd428e0389e3c0b59b] Merge remote-tracking branch 'drivers-x86/for-next'
git bisect good 4621ddca720ceb9b45725acd428e0389e3c0b59b
# good: [fac3dee864e971dff81dd4969c361b2b373109c0] Merge remote-tracking branch 'leds/for-next'
git bisect good fac3dee864e971dff81dd4969c361b2b373109c0
# good: [55c7549819e438f40a3ef1d8ac5c38b73390bcb7] scripts: add dummy report mode to add_namespace.cocci
git bisect good 55c7549819e438f40a3ef1d8ac5c38b73390bcb7
# good: [fe940d7362e6d7a5e5086581d0462e00ba766992] driver core: Drop mention of obsolete bus rwsem from kernel-doc
git bisect good fe940d7362e6d7a5e5086581d0462e00ba766992
# bad: [da6d647598a6d182eb6a0344a7b14ae005244399] driver core: Add waiting_for_supplier sysfs file for devices
git bisect bad da6d647598a6d182eb6a0344a7b14ae005244399
# bad: [8fd456ec0cf03875908d6b67c1cd20cf0a7b4474] driver core: Add state_synced sysfs file for devices that support it
git bisect bad 8fd456ec0cf03875908d6b67c1cd20cf0a7b4474
# bad: [287905e68dd29873bcb7986a8290cd1e4cfde600] driver core: Expose device link details in sysfs
git bisect bad 287905e68dd29873bcb7986a8290cd1e4cfde600
# first bad commit: [287905e68dd29873bcb7986a8290cd1e4cfde600] driver core: Expose device link details in sysfs

Re: [PATCH v3 1/3] driver core: Expose device link details in sysfs

[Saravana Kannan]

On Wed, Jul 15, 2020 at 3:14 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> Hi,
>
> On Thu, May 21, 2020 at 12:17:58PM -0700, Saravana Kannan wrote:
> > It's helpful to be able to look at device link details from sysfs. So,
> > expose it in sysfs.
> >
> > Say device-A is supplier of device-B. These are the additional files
> > this patch would create:
> >
> >
> > Signed-off-by: Saravana Kannan <saravanak@google.com>
>
> This patch creates a lot of noise in linux-next when booting various
> qemu images. Example log output as well as bisect results below.
> Reverting the patch fixes the problem.

Thanks for reporting it. Marek reported it last night too. I'll take a
look at this before the end of the week (probably tomorrow).

-Saravana