Hi Loic,
On 10/26/20 10:34 AM, Loic Poulain wrote:
Hi Hemant,
That looks better IMHO, just small comments on locking.
[..]
+static ssize_t mhi_uci_write(struct file *file,
+ const char __user *buf,
+ size_t count,
+ loff_t *offp)
+{
+ struct uci_dev *udev = file->private_data;
+ struct mhi_device *mhi_dev = udev->mhi_dev;
+ struct device *dev = &mhi_dev->dev;
+ struct uci_chan *uchan = udev->uchan;
+ size_t bytes_xfered = 0;
+ int ret, nr_avail = 0;
+
+ /* if ul channel is not supported return error */
+ if (!buf || !count || !mhi_dev->ul_chan)
+ return -EINVAL;
+
+ dev_dbg(dev, "%s: to xfer: %zu bytes\n", __func__, count);
+
+ mutex_lock(&uchan->write_lock);
Maybe mutex_lock_interruptible is more appropriate here (same in read fops).
i agree, will return -EINTR if mutex_lock_interruptible returns < 0.
[..]
+static ssize_t mhi_uci_read(struct file *file,
+ char __user *buf,
+ size_t count,
+ loff_t *ppos)
+{
+ struct uci_dev *udev = file->private_data;
+ struct mhi_device *mhi_dev = udev->mhi_dev;
+ struct uci_chan *uchan = udev->uchan;
+ struct device *dev = &mhi_dev->dev;
+ struct uci_buf *ubuf;
+ size_t rx_buf_size;
+ char *ptr;
+ size_t to_copy;
+ int ret = 0;
+
+ /* if dl channel is not supported return error */
+ if (!buf || !mhi_dev->dl_chan)
+ return -EINVAL;
+
+ mutex_lock(&uchan->read_lock);
+ spin_lock_bh(&uchan->dl_pending_lock);
+ /* No data available to read, wait */
+ if (!uchan->cur_buf && list_empty(&uchan->dl_pending)) {
+ dev_dbg(dev, "No data available to read, waiting\n");
+
+ spin_unlock_bh(&uchan->dl_pending_lock);
+ ret = wait_event_interruptible(uchan->dl_wq,
+ (!udev->enabled ||
+
!list_empty(&uchan->dl_pending)));
If you need to protect dl_pending list against concurent access, you
need to do it in wait_event as well. I would suggest to lookg at
`wait_event_interruptible_lock_irq` function, that allows to pass a
locked spinlock as parameter. That would be safer and prevent this
lock/unlock dance.
When using this API difference is, first we take spin_lock_bh() and then
wait API is using spin_unlock_irq()/spin_lock_irq(). I am getting
"BUG: scheduling while atomic" when i use this way. When i changed
spin_lock_bh to spin_lock_irq then we got rid of the kernel BUG.
Thanks,
Hemant
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