Oliver Neukum <oneukum@xxxxxxxx> wrote:
>
> On 17.09.24 12:01, Jeongjun Park wrote:
>
> > Okay, I understand. Then I think it would be appropriate to do
> > the patch below to prevent blocking, but I have one question.
> >
> > Currently, many misc usb drivers do not seem to handle the
> > O_NONBLOCK flag when using mutex_lock. If this is really
>
> Yes. The quality of many drivers could be improved.
> Feel free to make patches. However, the lack of quality elsewhere
> does not justify a regression. Hence code fixing drivers already
> correctly supporting O_NONBLOCK must be correct in that regard.
>
> > necessary code, I think it would require code modifications to
> > other functions inside iowarrior and many misc usb drivers.
> >
> > What do you think about this?
>
> The formatting seems to be broken. In terms of content it is good.
Oh, this format was sent broken. I'm sending you the patch below again.
I'll send you a new patch with this patch right away.
And I'll try to write a patch for other functions and misc usbs that don't
support O_NONBLOCK properly soon.
Regards,
Jeongjun Park
---
drivers/usb/misc/iowarrior.c | 46 ++++++++++++++++++++++++++++--------
1 file changed, 36 insertions(+), 10 deletions(-)
diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c
index 6d28467ce352..dbf0ed04f7c3 100644
--- a/drivers/usb/misc/iowarrior.c
+++ b/drivers/usb/misc/iowarrior.c
@@ -277,28 +277,45 @@ static ssize_t iowarrior_read(struct file *file, char __user *buffer,
struct iowarrior *dev;
int read_idx;
int offset;
+ int retval = 0;
dev = file->private_data;
+ if (file->f_flags & O_NONBLOCK) {
+ retval = mutex_trylock(&dev->mutex);
+ if (!retval)
+ return -EAGAIN;
+ } else {
+ retval = mutex_lock_interruptible(&dev->mutex);
+ if (retval)
+ return -ERESTARTSYS;
+ }
+
/* verify that the device wasn't unplugged */
- if (!dev || !dev->present)
- return -ENODEV;
+ if (!dev->present) {
+ retval = -ENODEV;
+ goto exit;
+ }
dev_dbg(&dev->interface->dev, "minor %d, count = %zd\n",
dev->minor, count);
/* read count must be packet size (+ time stamp) */
if ((count != dev->report_size)
- && (count != (dev->report_size + 1)))
- return -EINVAL;
+ && (count != (dev->report_size + 1))) {
+ retval = -EINVAL;
+ goto exit;
+ }
/* repeat until no buffer overrun in callback handler occur */
do {
atomic_set(&dev->overflow_flag, 0);
if ((read_idx = read_index(dev)) == -1) {
/* queue empty */
- if (file->f_flags & O_NONBLOCK)
- return -EAGAIN;
+ if (file->f_flags & O_NONBLOCK) {
+ retval = -EAGAIN;
+ goto exit;
+ }
else {
//next line will return when there is either new data, or the device is unplugged
int r = wait_event_interruptible(dev->read_wait,
@@ -309,28 +326,37 @@ static ssize_t iowarrior_read(struct file *file, char __user *buffer,
-1));
if (r) {
//we were interrupted by a signal
- return -ERESTART;
+ retval = -ERESTART;
+ goto exit;
}
if (!dev->present) {
//The device was unplugged
- return -ENODEV;
+ retval = -ENODEV;
+ goto exit;
}
if (read_idx == -1) {
// Can this happen ???
- return 0;
+ retval = 0;
+ goto exit;
}
}
}
offset = read_idx * (dev->report_size + 1);
if (copy_to_user(buffer, dev->read_queue + offset, count)) {
- return -EFAULT;
+ retval = -EFAULT;
+ goto exit;
}
} while (atomic_read(&dev->overflow_flag));
read_idx = ++read_idx == MAX_INTERRUPT_BUFFER ? 0 : read_idx;
atomic_set(&dev->read_idx, read_idx);
+ mutex_unlock(&dev->mutex);
return count;
+
+exit:
+ mutex_unlock(&dev->mutex);
+ return retval;
}
/*
--
>
> Regards
> Oliver
