Am Sonntag, den 20.09.2020, 10:44 +0200 schrieb Pavel Machek:
> Move prepare to wait around, so that normal GFP_KERNEL allocation can
> be used.
> 
> Signed-off-by: Pavel Machek (CIP) <pa...@denx.de>
> Acked-by: Alan Stern <st...@rowland.harvard.edu>

Ehm. Please recheck.

> diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
> index b2e09883c7e2..071f1debebba 100644
> --- a/drivers/usb/misc/yurex.c
> +++ b/drivers/usb/misc/yurex.c
> @@ -489,10 +489,10 @@ static ssize_t yurex_write(struct file *file, const 
> char __user *user_buffer,
>       }
>  
>       /* send the data as the control msg */
> -     prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
>       dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
>               dev->cntl_buffer[0]);
> -     retval = usb_submit_urb(dev->cntl_urb, GFP_ATOMIC);
> +     retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);

URB completes here. wake_up() returns the task to RUNNING.

> +     prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);

Task goes to TASK_INTERRUPTIBLE

>       if (retval >= 0)
>               timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);

Task turns into Sleeping Beauty until timeout

>       finish_wait(&dev->waitq, &wait);

And here task goes into error reporting as it checks timeout.

        Regards
                Oliver

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