[PATCH v4 3/3] usb: gadget: udc: core: Offload usb_udc_vbus_handler processing

From: Badhri Jagan Sridharan
Date: Mon May 29 2023 - 19:48:40 EST

chipidea udc calls usb_udc_vbus_handler from udc_start gadget
ops causing a deadlock. Avoid this by offloading usb_udc_vbus_handler
processing.

============================================
WARNING: possible recursive locking detected
640-rc1-000-devel-00005-gcda3c69ebc14 #1 Not tainted
-------------------------------------------

CPU0
----
lock(&udc->connect_lock);
lock(&udc->connect_lock);

DEADLOCK

stack backtrace:
CPU: 1 PID: 566 Comm: echo Not tainted 640-rc1-000-devel-00005-gcda3c69ebc14 #1
Hardware name: Freescale iMX7 Dual (Device Tree)
unwind_backtrace from show_stack+0x10/0x14
show_stack from dump_stack_lvl+0x70/0xb0
dump_stack_lvl from __lock_acquire+0x924/0x22c4
__lock_acquire from lock_acquire+0x100/0x370
lock_acquire from __mutex_lock+0xa8/0xfb4
__mutex_lock from mutex_lock_nested+0x1c/0x24
mutex_lock_nested from usb_udc_vbus_handler+0x1c/0x60
usb_udc_vbus_handler from ci_udc_start+0x74/0x9c
ci_udc_start from gadget_bind_driver+0x130/0x230
gadget_bind_driver from really_probe+0xd8/0x3fc
really_probe from __driver_probe_device+0x94/0x1f0
__driver_probe_device from driver_probe_device+0x2c/0xc4
driver_probe_device from __driver_attach+0x114/0x1cc
__driver_attach from bus_for_each_dev+0x7c/0xcc
bus_for_each_dev from bus_add_driver+0xd4/0x200
bus_add_driver from driver_register+0x7c/0x114
driver_register from usb_gadget_register_driver_owner+0x40/0xe0
usb_gadget_register_driver_owner from gadget_dev_desc_UDC_store+0xd4/0x110
gadget_dev_desc_UDC_store from configfs_write_iter+0xac/0x118
configfs_write_iter from vfs_write+0x1b4/0x40c
vfs_write from ksys_write+0x70/0xf8
ksys_write from ret_fast_syscall+0x0/0x1c

Fixes: 0db213ea8eed ("Revert "Revert "usb: gadget: udc: core: Prevent redundant calls to pullup""")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Stephan Gerhold <stephan@xxxxxxxxxxx>
Closes: https://lore.kernel.org/all/ZF4bMptC3Lf2Hnee@xxxxxxxxxxx/
Reported-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
Closes: https://lore.kernel.org/all/ZF4BvgsOyoKxdPFF@xxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Reported-by: Alistair <alistair@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/0cf8c588b701d7cf25ffe1a9217b81716e6a5c51.camel@xxxxxxxxxxxxx/
Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
---
Changes since v1:
- Address Alan Stern's comment on usb_udc_vbus_handler invocation from
atomic context:
* vbus_events_lock is now a spinlock and allocations in
* usb_udc_vbus_handler are atomic now.

Changes since v2:
- Addressing Alan Stern's comments:
** connect_lock is now held by callers of
* usb_gadget_pullup_update_locked() and gadget_(un)bind_driver() does
* notdirectly hold the lock.

** Both usb_gadget_(dis)connect() and usb_udc_vbus_handler() would
* set/clear udc->vbus and invoke usb_gadget_pullup_update_locked.

** Add "unbinding" to prevent new connections after the gadget is being
* unbound.

Changes since v3:
** Made a minor cleanup which I missed to do in v3 in
* usb_udc_vbus_handler().
---
drivers/usb/gadget/udc/core.c | 269 ++++++++++++++++------------------
1 file changed, 123 insertions(+), 146 deletions(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 4641153e9706..26380e621e9f 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -38,9 +38,10 @@ static const struct bus_type gadget_bus_type;
* for udcs who do not care about vbus status, this value is always true
* @started: the UDC's started state. True if the UDC had started.
* @connect_lock: protects udc->vbus, udc->started, gadget->connect, gadget->deactivate related
- * functions. usb_gadget_connect_locked, usb_gadget_disconnect_locked,
- * usb_udc_connect_control_locked, usb_gadget_udc_start_locked, usb_gadget_udc_stop_locked are
- * called with this lock held.
+ * functions. usb_gadget_pullup_update_locked called with this lock held.
+ * @vbus_events: list head for processing vbus updates on usb_udc_vbus_handler.
+ * @vbus_events_lock: protects vbus_events list
+ * @vbus_work: work item that invokes usb_gadget_pullup_update_locked.
*
* This represents the internal data structure which is used by the UDC-class
* to hold information about udc driver and gadget together.
@@ -53,6 +54,20 @@ struct usb_udc {
bool vbus;
bool started;
struct mutex connect_lock;
+ struct list_head vbus_events;
+ spinlock_t vbus_events_lock;
+ struct work_struct vbus_work;
+ bool unbinding;
+};
+
+/**
+ * struct vbus_event - used to notify vbus updates posted through usb_udc_vbus_handler.
+ * @vbus_on: true when vbus is on. false other wise.
+ * @node: list node for maintaining a list of pending updates to be processed.
+ */
+struct vbus_event {
+ bool vbus_on;
+ struct list_head node;
};

static struct class *udc_class;
@@ -693,40 +708,46 @@ int usb_gadget_vbus_disconnect(struct usb_gadget *gadget)
EXPORT_SYMBOL_GPL(usb_gadget_vbus_disconnect);

/* Internal version of usb_gadget_connect needs to be called with connect_lock held. */
-static int usb_gadget_connect_locked(struct usb_gadget *gadget)
+static int usb_gadget_pullup_update_locked(struct usb_gadget *gadget)
__must_hold(&gadget->udc->connect_lock)
{
int ret = 0;
+ bool connect = !gadget->deactivated && gadget->udc->started && gadget->udc->vbus &&
+ !gadget->udc->unbinding;

if (!gadget->ops->pullup) {
ret = -EOPNOTSUPP;
goto out;
}

- if (gadget->connected)
- goto out;
-
- if (gadget->deactivated || !gadget->udc->started) {
- /*
- * If gadget is deactivated we only save new state.
- * Gadget will be connected automatically after activation.
- *
- * udc first needs to be started before gadget can be pulled up.
- */
- gadget->connected = true;
- goto out;
+ if (connect != gadget->connected) {
+ ret = gadget->ops->pullup(gadget, connect);
+ if (!ret)
+ gadget->connected = connect;
+ mutex_lock(&udc_lock);
+ if (!connect)
+ gadget->udc->driver->disconnect(gadget);
+ mutex_unlock(&udc_lock);
}

- ret = gadget->ops->pullup(gadget, 1);
- if (!ret)
- gadget->connected = 1;
-
out:
trace_usb_gadget_connect(gadget, ret);

return ret;
}

+static int usb_gadget_set_vbus(struct usb_gadget *gadget, bool vbus)
+{
+ int ret;
+
+ mutex_lock(&gadget->udc->connect_lock);
+ gadget->udc->vbus = vbus;
+ ret = usb_gadget_pullup_update_locked(gadget);
+ mutex_unlock(&gadget->udc->connect_lock);
+
+ return ret;
+}
+
/**
* usb_gadget_connect - software-controlled connect to USB host
* @gadget:the peripheral being connected
@@ -739,56 +760,10 @@ static int usb_gadget_connect_locked(struct usb_gadget *gadget)
*/
int usb_gadget_connect(struct usb_gadget *gadget)
{
- int ret;
-
- mutex_lock(&gadget->udc->connect_lock);
- ret = usb_gadget_connect_locked(gadget);
- mutex_unlock(&gadget->udc->connect_lock);
-
- return ret;
+ return usb_gadget_set_vbus(gadget, true);
}
EXPORT_SYMBOL_GPL(usb_gadget_connect);

-/* Internal version of usb_gadget_disconnect needs to be called with connect_lock held. */
-static int usb_gadget_disconnect_locked(struct usb_gadget *gadget)
- __must_hold(&gadget->udc->connect_lock)
-{
- int ret = 0;
-
- if (!gadget->ops->pullup) {
- ret = -EOPNOTSUPP;
- goto out;
- }
-
- if (!gadget->connected)
- goto out;
-
- if (gadget->deactivated || !gadget->udc->started) {
- /*
- * If gadget is deactivated we only save new state.
- * Gadget will stay disconnected after activation.
- *
- * udc should have been started before gadget being pulled down.
- */
- gadget->connected = false;
- goto out;
- }
-
- ret = gadget->ops->pullup(gadget, 0);
- if (!ret)
- gadget->connected = 0;
-
- mutex_lock(&udc_lock);
- if (gadget->udc->driver)
- gadget->udc->driver->disconnect(gadget);
- mutex_unlock(&udc_lock);
-
-out:
- trace_usb_gadget_disconnect(gadget, ret);
-
- return ret;
-}
-
/**
* usb_gadget_disconnect - software-controlled disconnect from USB host
* @gadget:the peripheral being disconnected
@@ -803,16 +778,22 @@ static int usb_gadget_disconnect_locked(struct usb_gadget *gadget)
* Returns zero on success, else negative errno.
*/
int usb_gadget_disconnect(struct usb_gadget *gadget)
+{
+ return usb_gadget_set_vbus(gadget, false);
+}
+EXPORT_SYMBOL_GPL(usb_gadget_disconnect);
+
+static int usb_gadget_set_deactivate(struct usb_gadget *gadget, bool deactivate)
{
int ret;

mutex_lock(&gadget->udc->connect_lock);
- ret = usb_gadget_disconnect_locked(gadget);
+ gadget->deactivated = deactivate;
+ ret = usb_gadget_pullup_update_locked(gadget);
mutex_unlock(&gadget->udc->connect_lock);

return ret;
}
-EXPORT_SYMBOL_GPL(usb_gadget_disconnect);

/**
* usb_gadget_deactivate - deactivate function which is not ready to work
@@ -829,26 +810,7 @@ int usb_gadget_deactivate(struct usb_gadget *gadget)
{
int ret = 0;

- if (gadget->deactivated)
- goto out;
-
- mutex_lock(&gadget->udc->connect_lock);
- if (gadget->connected) {
- ret = usb_gadget_disconnect_locked(gadget);
- if (ret)
- goto unlock;
-
- /*
- * If gadget was being connected before deactivation, we want
- * to reconnect it in usb_gadget_activate().
- */
- gadget->connected = true;
- }
- gadget->deactivated = true;
-
-unlock:
- mutex_unlock(&gadget->udc->connect_lock);
-out:
+ ret = usb_gadget_set_deactivate(gadget, true);
trace_usb_gadget_deactivate(gadget, ret);

return ret;
@@ -868,21 +830,7 @@ int usb_gadget_activate(struct usb_gadget *gadget)
{
int ret = 0;

- if (!gadget->deactivated)
- goto out;
-
- mutex_lock(&gadget->udc->connect_lock);
- gadget->deactivated = false;
-
- /*
- * If gadget has been connected before deactivation, or became connected
- * while it was being deactivated, we call usb_gadget_connect().
- */
- if (gadget->connected)
- ret = usb_gadget_connect_locked(gadget);
- mutex_unlock(&gadget->udc->connect_lock);
-
-out:
+ ret = usb_gadget_set_deactivate(gadget, false);
trace_usb_gadget_activate(gadget, ret);

return ret;
@@ -1121,13 +1069,28 @@ EXPORT_SYMBOL_GPL(usb_gadget_set_state);

/* ------------------------------------------------------------------------- */

-/* Acquire connect_lock before calling this function. */
-static void usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc->connect_lock)
+static void vbus_event_work(struct work_struct *work)
{
- if (udc->vbus && udc->started)
- usb_gadget_connect_locked(udc->gadget);
- else
- usb_gadget_disconnect_locked(udc->gadget);
+ struct vbus_event *event, *n;
+ struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
+ unsigned long flags;
+
+ spin_lock_irqsave(&udc->vbus_events_lock, flags);
+ list_for_each_entry_safe(event, n, &udc->vbus_events, node) {
+ list_del(&event->node);
+ /* OK to drop the lock here as it suffice to syncrhronize udc->vbus_events node
+ * retrieval and deletion against usb_udc_vbus_handler. usb_udc_vbus_handler does
+ * list_add_tail so n would be the same even if the lock is dropped.
+ */
+ spin_unlock_irqrestore(&udc->vbus_events_lock, flags);
+ mutex_lock(&udc->connect_lock);
+ udc->vbus = event->vbus_on;
+ usb_gadget_pullup_update_locked(udc->gadget);
+ kfree(event);
+ mutex_unlock(&udc->connect_lock);
+ spin_lock_irqsave(&udc->vbus_events_lock, flags);
+ }
+ spin_unlock_irqrestore(&udc->vbus_events_lock, flags);
}

/**
@@ -1141,14 +1104,24 @@ static void usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc
*/
void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
{
- struct usb_udc *udc = gadget->udc;
+ struct usb_udc *udc;
+ struct vbus_event *vbus_event;
+ unsigned long flags;

- mutex_lock(&udc->connect_lock);
- if (udc) {
- udc->vbus = status;
- usb_udc_connect_control_locked(udc);
- }
- mutex_unlock(&udc->connect_lock);
+ if (!gadget || !gadget->udc)
+ return;
+
+ udc = gadget->udc;
+
+ vbus_event = kzalloc(sizeof(*vbus_event), GFP_ATOMIC);
+ if (!vbus_event)
+ return;
+
+ spin_lock_irqsave(&udc->vbus_events_lock, flags);
+ vbus_event->vbus_on = status;
+ list_add_tail(&vbus_event->node, &udc->vbus_events);
+ spin_unlock_irqrestore(&udc->vbus_events_lock, flags);
+ schedule_work(&udc->vbus_work);
}
EXPORT_SYMBOL_GPL(usb_udc_vbus_handler);

@@ -1170,7 +1143,7 @@ void usb_gadget_udc_reset(struct usb_gadget *gadget,
EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);

/**
- * usb_gadget_udc_start_locked - tells usb device controller to start up
+ * usb_gadget_udc_start - tells usb device controller to start up
* @udc: The UDC to be started
*
* This call is issued by the UDC Class driver when it's about
@@ -1181,11 +1154,8 @@ EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
* necessary to have it powered on.
*
* Returns zero on success, else negative errno.
- *
- * Caller should acquire connect_lock before invoking this function.
*/
-static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
- __must_hold(&udc->connect_lock)
+static inline int usb_gadget_udc_start(struct usb_udc *udc)
{
int ret;

@@ -1194,15 +1164,17 @@ static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
return -EBUSY;
}

+ mutex_lock(&udc->connect_lock);
ret = udc->gadget->ops->udc_start(udc->gadget, udc->driver);
if (!ret)
udc->started = true;
+ mutex_unlock(&udc->connect_lock);

return ret;
}

/**
- * usb_gadget_udc_stop_locked - tells usb device controller we don't need it anymore
+ * usb_gadget_udc_stop - tells usb device controller we don't need it anymore
* @udc: The UDC to be stopped
*
* This call is issued by the UDC Class driver after calling
@@ -1211,19 +1183,18 @@ static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
* The details are implementation specific, but it can go as
* far as powering off UDC completely and disable its data
* line pullups.
- *
- * Caller should acquire connect lock before invoking this function.
*/
-static inline void usb_gadget_udc_stop_locked(struct usb_udc *udc)
- __must_hold(&udc->connect_lock)
+static inline void usb_gadget_udc_stop(struct usb_udc *udc)
{
if (!udc->started) {
dev_err(&udc->dev, "UDC had already stopped\n");
return;
}

+ mutex_lock(&udc->connect_lock);
udc->gadget->ops->udc_stop(udc->gadget);
udc->started = false;
+ mutex_unlock(&udc->connect_lock);
}

/**
@@ -1362,6 +1333,7 @@ int usb_add_gadget(struct usb_gadget *gadget)
if (!udc)
goto error;

+ udc->unbinding = true;
device_initialize(&udc->dev);
udc->dev.release = usb_udc_release;
udc->dev.class = udc_class;
@@ -1375,6 +1347,9 @@ int usb_add_gadget(struct usb_gadget *gadget)
udc->gadget = gadget;
gadget->udc = udc;
mutex_init(&udc->connect_lock);
+ INIT_LIST_HEAD(&udc->vbus_events);
+ spin_lock_init(&udc->vbus_events_lock);
+ INIT_WORK(&udc->vbus_work, vbus_event_work);

udc->started = false;

@@ -1474,6 +1449,17 @@ char *usb_get_gadget_udc_name(void)
}
EXPORT_SYMBOL_GPL(usb_get_gadget_udc_name);

+static int usb_gadget_set_unbinding(struct usb_udc *udc, bool status)
+{
+ int ret;
+
+ mutex_lock(&udc->connect_lock);
+ udc->unbinding = status;
+ ret = usb_gadget_pullup_update_locked(udc->gadget);
+ mutex_unlock(&udc->connect_lock);
+
+ return ret;
+}
/**
* usb_add_gadget_udc - adds a new gadget to the udc class driver list
* @parent: the parent device to this udc. Usually the controller
@@ -1576,15 +1562,11 @@ static int gadget_bind_driver(struct device *dev)
if (ret)
goto err_bind;

- mutex_lock(&udc->connect_lock);
- ret = usb_gadget_udc_start_locked(udc);
- if (ret) {
- mutex_unlock(&udc->connect_lock);
+ ret = usb_gadget_udc_start(udc);
+ if (ret)
goto err_start;
- }
usb_gadget_enable_async_callbacks(udc);
- usb_udc_connect_control_locked(udc);
- mutex_unlock(&udc->connect_lock);
+ usb_gadget_set_unbinding(udc, false);

kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
return 0;
@@ -1615,14 +1597,13 @@ static void gadget_unbind_driver(struct device *dev)

kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);

- mutex_lock(&udc->connect_lock);
- usb_gadget_disconnect_locked(gadget);
+ usb_gadget_set_unbinding(udc, true);
+ cancel_work_sync(&udc->vbus_work);
usb_gadget_disable_async_callbacks(udc);
if (gadget->irq)
synchronize_irq(gadget->irq);
udc->driver->unbind(gadget);
- usb_gadget_udc_stop_locked(udc);
- mutex_unlock(&udc->connect_lock);
+ usb_gadget_udc_stop(udc);

mutex_lock(&udc_lock);
driver->is_bound = false;
@@ -1708,15 +1689,11 @@ static ssize_t soft_connect_store(struct device *dev,
}

if (sysfs_streq(buf, "connect")) {
- mutex_lock(&udc->connect_lock);
- usb_gadget_udc_start_locked(udc);
- usb_gadget_connect_locked(udc->gadget);
- mutex_unlock(&udc->connect_lock);
+ usb_gadget_udc_start(udc);
+ usb_udc_vbus_handler(udc->gadget, true);
} else if (sysfs_streq(buf, "disconnect")) {
- mutex_lock(&udc->connect_lock);
- usb_gadget_disconnect_locked(udc->gadget);
- usb_gadget_udc_stop_locked(udc);
- mutex_unlock(&udc->connect_lock);
+ usb_udc_vbus_handler(udc->gadget, false);
+ usb_gadget_udc_stop(udc);
} else {
dev_err(dev, "unsupported command '%s'\n", buf);
ret = -EINVAL;
--
2.41.0.rc0.172.g3f132b7071-goog