On Friday, October 09, 2015 4:27 AM, Ian Abbott wrote:
> 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 <abbotti@xxxxxxxxx>
> ---
> 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 07bb197..88e9334 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;
> }
Ian,
No issues with this patch, just a comment:
checkpatch.pl reports some issue about the spinlock_t and mutex definitions
in comedidev.h:
CHECK: spinlock_t definition without comment
#177: FILE: drivers/staging/comedi/comedidev.h:177:
+ spinlock_t spin_lock;
CHECK: spinlock_t definition without comment
#540: FILE: drivers/staging/comedi/comedidev.h:540:
+ spinlock_t spinlock;
CHECK: struct mutex definition without comment
#541: FILE: drivers/staging/comedi/comedidev.h:541:
+ struct mutex mutex;
I know these are documented in the docbook comment for the structs but would
you mind adding some comments to the definitions to quiet checkpatch.pl?
Thanks,
Hartley
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