From d5eb3a742109015cd794e536fe0968197b917e05 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Fri, 9 Oct 2015 12:26:52 +0100 Subject: [PATCH] staging: comedi: don't use mutex when polling file The main mutex in a comedi device can get held for quite a while when processing comedi instructions, so for performance reasons, the "read" and "write" file operations do not use it; they use use the `attach_lock` rwsemaphore to protect against the comedi device becoming detached at an inopportune moment. Do the same for the "poll" file operation. Signed-off-by: Ian Abbott Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 1d6bef285821..fe25287c5688 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -2264,7 +2264,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) struct comedi_device *dev = cfp->dev; struct comedi_subdevice *s, *s_read; - mutex_lock(&dev->mutex); + down_read(&dev->attach_lock); if (!dev->attached) { dev_dbg(dev->class_dev, "no driver attached\n"); @@ -2294,7 +2294,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) } done: - mutex_unlock(&dev->mutex); + up_read(&dev->attach_lock); return mask; } -- 2.20.1