Messages in this thread | | | Subject | Re: [PATCH v9 4/4] bus: mhi: Add userspace client interface driver | From | Hemant Kumar <> | Date | Mon, 26 Oct 2020 18:18:57 -0700 |
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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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