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Subject[PATCH 4.10 119/167] usb: gadget: f_hid: Use spinlock instead of mutex
Date
4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Krzysztof Opasiak <kopasiak90@gmail.com>

commit 33e4c1a9987a1fc3b42c3b534100b5b006d55c61 upstream.

As IN request has to be allocated in set_alt() and released in
disable() we cannot use mutex to protect it as we cannot sleep
in those funcitons. Let's replace this mutex with a spinlock.

Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/gadget/function/f_hid.c | 57 +++++++++++++++++++++---------------
1 file changed, 34 insertions(+), 23 deletions(-)

--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -50,12 +50,12 @@ struct f_hidg {

/* recv report */
struct list_head completed_out_req;
- spinlock_t spinlock;
+ spinlock_t read_spinlock;
wait_queue_head_t read_queue;
unsigned int qlen;

/* send report */
- struct mutex lock;
+ spinlock_t write_spinlock;
bool write_pending;
wait_queue_head_t write_queue;
struct usb_request *req;
@@ -258,20 +258,20 @@ static ssize_t f_hidg_read(struct file *
if (!access_ok(VERIFY_WRITE, buffer, count))
return -EFAULT;

- spin_lock_irqsave(&hidg->spinlock, flags);
+ spin_lock_irqsave(&hidg->read_spinlock, flags);

#define READ_COND (!list_empty(&hidg->completed_out_req))

/* wait for at least one buffer to complete */
while (!READ_COND) {
- spin_unlock_irqrestore(&hidg->spinlock, flags);
+ spin_unlock_irqrestore(&hidg->read_spinlock, flags);
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;

if (wait_event_interruptible(hidg->read_queue, READ_COND))
return -ERESTARTSYS;

- spin_lock_irqsave(&hidg->spinlock, flags);
+ spin_lock_irqsave(&hidg->read_spinlock, flags);
}

/* pick the first one */
@@ -286,7 +286,7 @@ static ssize_t f_hidg_read(struct file *

req = list->req;
count = min_t(unsigned int, count, req->actual - list->pos);
- spin_unlock_irqrestore(&hidg->spinlock, flags);
+ spin_unlock_irqrestore(&hidg->read_spinlock, flags);

/* copy to user outside spinlock */
count -= copy_to_user(buffer, req->buf + list->pos, count);
@@ -308,9 +308,9 @@ static ssize_t f_hidg_read(struct file *
return ret;
}
} else {
- spin_lock_irqsave(&hidg->spinlock, flags);
+ spin_lock_irqsave(&hidg->read_spinlock, flags);
list_add(&list->list, &hidg->completed_out_req);
- spin_unlock_irqrestore(&hidg->spinlock, flags);
+ spin_unlock_irqrestore(&hidg->read_spinlock, flags);

wake_up(&hidg->read_queue);
}
@@ -321,13 +321,16 @@ static ssize_t f_hidg_read(struct file *
static void f_hidg_req_complete(struct usb_ep *ep, struct usb_request *req)
{
struct f_hidg *hidg = (struct f_hidg *)ep->driver_data;
+ unsigned long flags;

if (req->status != 0) {
ERROR(hidg->func.config->cdev,
"End Point Request ERROR: %d\n", req->status);
}

+ spin_lock_irqsave(&hidg->write_spinlock, flags);
hidg->write_pending = 0;
+ spin_unlock_irqrestore(&hidg->write_spinlock, flags);
wake_up(&hidg->write_queue);
}

@@ -335,18 +338,19 @@ static ssize_t f_hidg_write(struct file
size_t count, loff_t *offp)
{
struct f_hidg *hidg = file->private_data;
+ unsigned long flags;
ssize_t status = -ENOMEM;

if (!access_ok(VERIFY_READ, buffer, count))
return -EFAULT;

- mutex_lock(&hidg->lock);
+ spin_lock_irqsave(&hidg->write_spinlock, flags);

#define WRITE_COND (!hidg->write_pending)

/* write queue */
while (!WRITE_COND) {
- mutex_unlock(&hidg->lock);
+ spin_unlock_irqrestore(&hidg->write_spinlock, flags);
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;

@@ -354,17 +358,20 @@ static ssize_t f_hidg_write(struct file
hidg->write_queue, WRITE_COND))
return -ERESTARTSYS;

- mutex_lock(&hidg->lock);
+ spin_lock_irqsave(&hidg->write_spinlock, flags);
}

+ hidg->write_pending = 1;
count = min_t(unsigned, count, hidg->report_length);
+
+ spin_unlock_irqrestore(&hidg->write_spinlock, flags);
status = copy_from_user(hidg->req->buf, buffer, count);

if (status != 0) {
ERROR(hidg->func.config->cdev,
"copy_from_user error\n");
- mutex_unlock(&hidg->lock);
- return -EINVAL;
+ status = -EINVAL;
+ goto release_write_pending;
}

hidg->req->status = 0;
@@ -372,19 +379,23 @@ static ssize_t f_hidg_write(struct file
hidg->req->length = count;
hidg->req->complete = f_hidg_req_complete;
hidg->req->context = hidg;
- hidg->write_pending = 1;

status = usb_ep_queue(hidg->in_ep, hidg->req, GFP_ATOMIC);
if (status < 0) {
ERROR(hidg->func.config->cdev,
"usb_ep_queue error on int endpoint %zd\n", status);
- hidg->write_pending = 0;
- wake_up(&hidg->write_queue);
+ goto release_write_pending;
} else {
status = count;
}

- mutex_unlock(&hidg->lock);
+ return status;
+release_write_pending:
+ spin_lock_irqsave(&hidg->write_spinlock, flags);
+ hidg->write_pending = 0;
+ spin_unlock_irqrestore(&hidg->write_spinlock, flags);
+
+ wake_up(&hidg->write_queue);

return status;
}
@@ -451,9 +462,9 @@ static void hidg_set_report_complete(str

req_list->req = req;

- spin_lock_irqsave(&hidg->spinlock, flags);
+ spin_lock_irqsave(&hidg->read_spinlock, flags);
list_add_tail(&req_list->list, &hidg->completed_out_req);
- spin_unlock_irqrestore(&hidg->spinlock, flags);
+ spin_unlock_irqrestore(&hidg->read_spinlock, flags);

wake_up(&hidg->read_queue);
break;
@@ -577,13 +588,13 @@ static void hidg_disable(struct usb_func
usb_ep_disable(hidg->in_ep);
usb_ep_disable(hidg->out_ep);

- spin_lock_irqsave(&hidg->spinlock, flags);
+ spin_lock_irqsave(&hidg->read_spinlock, flags);
list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
free_ep_req(hidg->out_ep, list->req);
list_del(&list->list);
kfree(list);
}
- spin_unlock_irqrestore(&hidg->spinlock, flags);
+ spin_unlock_irqrestore(&hidg->read_spinlock, flags);
}

static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
@@ -743,8 +754,8 @@ static int hidg_bind(struct usb_configur
if (status)
goto fail;

- mutex_init(&hidg->lock);
- spin_lock_init(&hidg->spinlock);
+ spin_lock_init(&hidg->write_spinlock);
+ spin_lock_init(&hidg->read_spinlock);
init_waitqueue_head(&hidg->write_queue);
init_waitqueue_head(&hidg->read_queue);
INIT_LIST_HEAD(&hidg->completed_out_req);

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