usb_udc_vbus_handler() can be invoked from interrupt context by irq
handlers of the gadget drivers, however, usb_udc_connect_control() has
to run in non-atomic context due to the following:
a. Some of the gadget driver implementations expect the ->pullup
callback to be invoked in non-atomic context.
b. usb_gadget_disconnect() acquires udc_lock which is a mutex.
Hence offload invocation of usb_udc_connect_control()
to workqueue.
UDC should not be pulled up unless gadget driver is bound. The new flag
"allow_connect" is now set by gadget_bind_driver() and cleared by
gadget_unbind_driver(). This prevents work item to pull up the gadget
even if queued when the gadget driver is already unbound.
Cc: [email protected]
Fixes: 1016fc0c096c ("USB: gadget: Fix obscure lockdep violation for udc_mutex")
Signed-off-by: Badhri Jagan Sridharan <[email protected]>
Reviewed-by: Alan Stern <[email protected]>
---
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().
Changes since v4:
- Addressing Alan Stern's comments:
** usb_udc_vbus_handler() now offloads invocation of usb_udc_connect_control()
* from workqueue.
** Dropped vbus_events list as this was redundant. Updating to the
* latest value is suffice
Changes since v5:
- Addressing Alan Stern's comments:
** Squashed allow_connect logic to this patch.
** Fixed comment length to wrap at 76
** Cancelling vbus_work in del_gadget()
Changes since v6:
- Added reviewed by tag
Changes since v7:
- None
---
drivers/usb/gadget/udc/core.c | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 52e6d2e84e35..d2e4f78c53e3 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -37,6 +37,9 @@ static const struct bus_type gadget_bus_type;
* @vbus: for udcs who care about vbus status, this value is real vbus status;
* 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.
+ * @allow_connect: Indicates whether UDC is allowed to be pulled up.
+ * Set/cleared by gadget_(un)bind_driver() after gadget driver is bound or
+ * unbound.
*
* This represents the internal data structure which is used by the UDC-class
* to hold information about udc driver and gadget together.
@@ -48,6 +51,8 @@ struct usb_udc {
struct list_head list;
bool vbus;
bool started;
+ bool allow_connect;
+ struct work_struct vbus_work;
};
static struct class *udc_class;
@@ -706,7 +711,7 @@ int usb_gadget_connect(struct usb_gadget *gadget)
goto out;
}
- if (gadget->deactivated) {
+ if (gadget->deactivated || !gadget->udc->allow_connect) {
/*
* If gadget is deactivated we only save new state.
* Gadget will be connected automatically after activation.
@@ -1086,6 +1091,13 @@ static void usb_udc_connect_control(struct usb_udc *udc)
usb_gadget_disconnect(udc->gadget);
}
+static void vbus_event_work(struct work_struct *work)
+{
+ struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
+
+ usb_udc_connect_control(udc);
+}
+
/**
* usb_udc_vbus_handler - updates the udc core vbus status, and try to
* connect or disconnect gadget
@@ -1094,6 +1106,14 @@ static void usb_udc_connect_control(struct usb_udc *udc)
*
* The udc driver calls it when it wants to connect or disconnect gadget
* according to vbus status.
+ *
+ * This function can be invoked from interrupt context by irq handlers of
+ * the gadget drivers, however, usb_udc_connect_control() has to run in
+ * non-atomic context due to the following:
+ * a. Some of the gadget driver implementations expect the ->pullup
+ * callback to be invoked in non-atomic context.
+ * b. usb_gadget_disconnect() acquires udc_lock which is a mutex.
+ * Hence offload invocation of usb_udc_connect_control() to workqueue.
*/
void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
{
@@ -1101,7 +1121,7 @@ void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
if (udc) {
udc->vbus = status;
- usb_udc_connect_control(udc);
+ schedule_work(&udc->vbus_work);
}
}
EXPORT_SYMBOL_GPL(usb_udc_vbus_handler);
@@ -1328,6 +1348,7 @@ int usb_add_gadget(struct usb_gadget *gadget)
mutex_lock(&udc_lock);
list_add_tail(&udc->list, &udc_list);
mutex_unlock(&udc_lock);
+ INIT_WORK(&udc->vbus_work, vbus_event_work);
ret = device_add(&udc->dev);
if (ret)
@@ -1459,6 +1480,7 @@ void usb_del_gadget(struct usb_gadget *gadget)
flush_work(&gadget->work);
device_del(&gadget->dev);
ida_free(&gadget_id_numbers, gadget->id_number);
+ cancel_work_sync(&udc->vbus_work);
device_unregister(&udc->dev);
}
EXPORT_SYMBOL_GPL(usb_del_gadget);
@@ -1527,6 +1549,7 @@ static int gadget_bind_driver(struct device *dev)
if (ret)
goto err_start;
usb_gadget_enable_async_callbacks(udc);
+ udc->allow_connect = true;
usb_udc_connect_control(udc);
kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
@@ -1558,6 +1581,8 @@ static void gadget_unbind_driver(struct device *dev)
kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
+ udc->allow_connect = false;
+ cancel_work_sync(&udc->vbus_work);
usb_gadget_disconnect(gadget);
usb_gadget_disable_async_callbacks(udc);
if (gadget->irq)
base-commit: d37537a1f7cf09e304fe7993cb5e732534a0fb22
--
2.41.0.162.gfafddb0af9-goog
usb_udc_connect_control(), soft_connect_store() and
usb_gadget_deactivate() can potentially race against each other to invoke
usb_gadget_connect()/usb_gadget_disconnect(). To prevent this, guard
udc->started, gadget->allow_connect, gadget->deactivate and
gadget->connect with connect_lock so that ->pullup() is only invoked when
the gadget is bound, started and not deactivated. The routines
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.
An earlier version of this commit was reverted due to the crash reported in
https://lore.kernel.org/all/[email protected]/.
commit 16737e78d190 ("usb: gadget: udc: core: Offload usb_udc_vbus_handler processing")
addresses the crash reported.
Cc: [email protected]
Fixes: 628ef0d273a6 ("usb: udc: add usb_udc_vbus_handler")
Signed-off-by: Badhri Jagan Sridharan <[email protected]>
---
v5 is the first version in this series.
Changes since v5:
** Fixed up commit message
** Wrapped comments at 76.
Changes since v6:
** Address Alan comments around style/presentation.
** Fixed code to acquire ->connect_lock before testing gadget->deactivated.
Changes since v7:
** Remove unused out labels reported by ktest robot
---
drivers/usb/gadget/udc/core.c | 155 +++++++++++++++++++++++-----------
1 file changed, 106 insertions(+), 49 deletions(-)
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index d2e4f78c53e3..83fd1de14784 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -40,6 +40,11 @@ static const struct bus_type gadget_bus_type;
* @allow_connect: Indicates whether UDC is allowed to be pulled up.
* Set/cleared by gadget_(un)bind_driver() after gadget driver is bound or
* unbound.
+ * @connect_lock: protects udc->started, gadget->connect,
+ * gadget->allow_connect and gadget->deactivate. The routines
+ * usb_gadget_connect_locked(), usb_gadget_disconnect_locked(),
+ * usb_udc_connect_control_locked(), usb_gadget_udc_start_locked() and
+ * usb_gadget_udc_stop_locked() are called with this lock held.
*
* This represents the internal data structure which is used by the UDC-class
* to hold information about udc driver and gadget together.
@@ -53,6 +58,7 @@ struct usb_udc {
bool started;
bool allow_connect;
struct work_struct vbus_work;
+ struct mutex connect_lock;
};
static struct class *udc_class;
@@ -692,17 +698,8 @@ int usb_gadget_vbus_disconnect(struct usb_gadget *gadget)
}
EXPORT_SYMBOL_GPL(usb_gadget_vbus_disconnect);
-/**
- * usb_gadget_connect - software-controlled connect to USB host
- * @gadget:the peripheral being connected
- *
- * Enables the D+ (or potentially D-) pullup. The host will start
- * enumerating this gadget when the pullup is active and a VBUS session
- * is active (the link is powered).
- *
- * Returns zero on success, else negative errno.
- */
-int usb_gadget_connect(struct usb_gadget *gadget)
+static int usb_gadget_connect_locked(struct usb_gadget *gadget)
+ __must_hold(&gadget->udc->connect_lock)
{
int ret = 0;
@@ -711,10 +708,12 @@ int usb_gadget_connect(struct usb_gadget *gadget)
goto out;
}
- if (gadget->deactivated || !gadget->udc->allow_connect) {
+ if (gadget->deactivated || !gadget->udc->allow_connect || !gadget->udc->started) {
/*
- * If gadget is deactivated we only save new state.
- * Gadget will be connected automatically after activation.
+ * If the gadget isn't usable (because it is deactivated,
+ * unbound, or not yet started), we only save the new state.
+ * The gadget will be connected automatically when it is
+ * activated/bound/started.
*/
gadget->connected = true;
goto out;
@@ -729,22 +728,31 @@ int usb_gadget_connect(struct usb_gadget *gadget)
return ret;
}
-EXPORT_SYMBOL_GPL(usb_gadget_connect);
/**
- * usb_gadget_disconnect - software-controlled disconnect from USB host
- * @gadget:the peripheral being disconnected
- *
- * Disables the D+ (or potentially D-) pullup, which the host may see
- * as a disconnect (when a VBUS session is active). Not all systems
- * support software pullup controls.
+ * usb_gadget_connect - software-controlled connect to USB host
+ * @gadget:the peripheral being connected
*
- * Following a successful disconnect, invoke the ->disconnect() callback
- * for the current gadget driver so that UDC drivers don't need to.
+ * Enables the D+ (or potentially D-) pullup. The host will start
+ * enumerating this gadget when the pullup is active and a VBUS session
+ * is active (the link is powered).
*
* Returns zero on success, else negative errno.
*/
-int usb_gadget_disconnect(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;
+}
+EXPORT_SYMBOL_GPL(usb_gadget_connect);
+
+static int usb_gadget_disconnect_locked(struct usb_gadget *gadget)
+ __must_hold(&gadget->udc->connect_lock)
{
int ret = 0;
@@ -756,7 +764,7 @@ int usb_gadget_disconnect(struct usb_gadget *gadget)
if (!gadget->connected)
goto out;
- if (gadget->deactivated) {
+ if (gadget->deactivated || !gadget->udc->started) {
/*
* If gadget is deactivated we only save new state.
* Gadget will stay disconnected after activation.
@@ -779,6 +787,30 @@ int usb_gadget_disconnect(struct usb_gadget *gadget)
return ret;
}
+
+/**
+ * usb_gadget_disconnect - software-controlled disconnect from USB host
+ * @gadget:the peripheral being disconnected
+ *
+ * Disables the D+ (or potentially D-) pullup, which the host may see
+ * as a disconnect (when a VBUS session is active). Not all systems
+ * support software pullup controls.
+ *
+ * Following a successful disconnect, invoke the ->disconnect() callback
+ * for the current gadget driver so that UDC drivers don't need to.
+ *
+ * Returns zero on success, else negative errno.
+ */
+int usb_gadget_disconnect(struct usb_gadget *gadget)
+{
+ int ret;
+
+ mutex_lock(&gadget->udc->connect_lock);
+ ret = usb_gadget_disconnect_locked(gadget);
+ mutex_unlock(&gadget->udc->connect_lock);
+
+ return ret;
+}
EXPORT_SYMBOL_GPL(usb_gadget_disconnect);
/**
@@ -796,13 +828,14 @@ int usb_gadget_deactivate(struct usb_gadget *gadget)
{
int ret = 0;
+ mutex_lock(&gadget->udc->connect_lock);
if (gadget->deactivated)
- goto out;
+ goto unlock;
if (gadget->connected) {
- ret = usb_gadget_disconnect(gadget);
+ ret = usb_gadget_disconnect_locked(gadget);
if (ret)
- goto out;
+ goto unlock;
/*
* If gadget was being connected before deactivation, we want
@@ -812,7 +845,8 @@ int usb_gadget_deactivate(struct usb_gadget *gadget)
}
gadget->deactivated = true;
-out:
+unlock:
+ mutex_unlock(&gadget->udc->connect_lock);
trace_usb_gadget_deactivate(gadget, ret);
return ret;
@@ -832,8 +866,9 @@ int usb_gadget_activate(struct usb_gadget *gadget)
{
int ret = 0;
+ mutex_lock(&gadget->udc->connect_lock);
if (!gadget->deactivated)
- goto out;
+ goto unlock;
gadget->deactivated = false;
@@ -842,9 +877,11 @@ int usb_gadget_activate(struct usb_gadget *gadget)
* while it was being deactivated, we call usb_gadget_connect().
*/
if (gadget->connected)
- ret = usb_gadget_connect(gadget);
+ ret = usb_gadget_connect_locked(gadget);
+ mutex_unlock(&gadget->udc->connect_lock);
-out:
+unlock:
+ mutex_unlock(&gadget->udc->connect_lock);
trace_usb_gadget_activate(gadget, ret);
return ret;
@@ -1083,19 +1120,22 @@ EXPORT_SYMBOL_GPL(usb_gadget_set_state);
/* ------------------------------------------------------------------------- */
-static void usb_udc_connect_control(struct usb_udc *udc)
+/* Acquire connect_lock before calling this function. */
+static void usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc->connect_lock)
{
if (udc->vbus)
- usb_gadget_connect(udc->gadget);
+ usb_gadget_connect_locked(udc->gadget);
else
- usb_gadget_disconnect(udc->gadget);
+ usb_gadget_disconnect_locked(udc->gadget);
}
static void vbus_event_work(struct work_struct *work)
{
struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
- usb_udc_connect_control(udc);
+ mutex_lock(&udc->connect_lock);
+ usb_udc_connect_control_locked(udc);
+ mutex_unlock(&udc->connect_lock);
}
/**
@@ -1144,7 +1184,7 @@ void usb_gadget_udc_reset(struct usb_gadget *gadget,
EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
/**
- * usb_gadget_udc_start - tells usb device controller to start up
+ * usb_gadget_udc_start_locked - 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
@@ -1155,8 +1195,11 @@ 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(struct usb_udc *udc)
+static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
+ __must_hold(&udc->connect_lock)
{
int ret;
@@ -1173,7 +1216,7 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
}
/**
- * usb_gadget_udc_stop - tells usb device controller we don't need it anymore
+ * usb_gadget_udc_stop_locked - 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
@@ -1182,8 +1225,11 @@ static inline int usb_gadget_udc_start(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(struct usb_udc *udc)
+static inline void usb_gadget_udc_stop_locked(struct usb_udc *udc)
+ __must_hold(&udc->connect_lock)
{
if (!udc->started) {
dev_err(&udc->dev, "UDC had already stopped\n");
@@ -1342,6 +1388,7 @@ int usb_add_gadget(struct usb_gadget *gadget)
udc->gadget = gadget;
gadget->udc = udc;
+ mutex_init(&udc->connect_lock);
udc->started = false;
@@ -1545,12 +1592,16 @@ static int gadget_bind_driver(struct device *dev)
if (ret)
goto err_bind;
- ret = usb_gadget_udc_start(udc);
- if (ret)
+ mutex_lock(&udc->connect_lock);
+ ret = usb_gadget_udc_start_locked(udc);
+ if (ret) {
+ mutex_unlock(&udc->connect_lock);
goto err_start;
+ }
usb_gadget_enable_async_callbacks(udc);
udc->allow_connect = true;
- usb_udc_connect_control(udc);
+ usb_udc_connect_control_locked(udc);
+ mutex_unlock(&udc->connect_lock);
kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
return 0;
@@ -1583,12 +1634,14 @@ static void gadget_unbind_driver(struct device *dev)
udc->allow_connect = false;
cancel_work_sync(&udc->vbus_work);
- usb_gadget_disconnect(gadget);
+ mutex_lock(&udc->connect_lock);
+ usb_gadget_disconnect_locked(gadget);
usb_gadget_disable_async_callbacks(udc);
if (gadget->irq)
synchronize_irq(gadget->irq);
udc->driver->unbind(gadget);
- usb_gadget_udc_stop(udc);
+ usb_gadget_udc_stop_locked(udc);
+ mutex_unlock(&udc->connect_lock);
mutex_lock(&udc_lock);
driver->is_bound = false;
@@ -1674,11 +1727,15 @@ static ssize_t soft_connect_store(struct device *dev,
}
if (sysfs_streq(buf, "connect")) {
- usb_gadget_udc_start(udc);
- usb_gadget_connect(udc->gadget);
+ mutex_lock(&udc->connect_lock);
+ usb_gadget_udc_start_locked(udc);
+ usb_gadget_connect_locked(udc->gadget);
+ mutex_unlock(&udc->connect_lock);
} else if (sysfs_streq(buf, "disconnect")) {
- usb_gadget_disconnect(udc->gadget);
- usb_gadget_udc_stop(udc);
+ mutex_lock(&udc->connect_lock);
+ usb_gadget_disconnect_locked(udc->gadget);
+ usb_gadget_udc_stop_locked(udc);
+ mutex_unlock(&udc->connect_lock);
} else {
dev_err(dev, "unsupported command '%s'\n", buf);
ret = -EINVAL;
--
2.41.0.162.gfafddb0af9-goog
On Fri, Jun 09, 2023 at 01:02:27AM +0000, Badhri Jagan Sridharan wrote:
> usb_udc_connect_control(), soft_connect_store() and
> usb_gadget_deactivate() can potentially race against each other to invoke
> usb_gadget_connect()/usb_gadget_disconnect(). To prevent this, guard
> udc->started, gadget->allow_connect, gadget->deactivate and
> gadget->connect with connect_lock so that ->pullup() is only invoked when
> the gadget is bound, started and not deactivated. The routines
> 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.
>
> An earlier version of this commit was reverted due to the crash reported in
> https://lore.kernel.org/all/[email protected]/.
> commit 16737e78d190 ("usb: gadget: udc: core: Offload usb_udc_vbus_handler processing")
> addresses the crash reported.
>
> Cc: [email protected]
> Fixes: 628ef0d273a6 ("usb: udc: add usb_udc_vbus_handler")
> Signed-off-by: Badhri Jagan Sridharan <[email protected]>
> ---
Reviewed-by: Alan Stern <[email protected]>