unlocked_ioctl vs normal ioctl

Question

In my driver\'s file_operations structure, I have:

struct file_operations Fops = {
  read:    device_read,
  write:   device_write,
  unlocked_ioctl:   device_io         


        

Answer 1

Read this LWN article: http://lwn.net/Articles/119652/

Also sometime between 2.6.33 and a 2.6.35 rc (use git-diff to find out which commit) the kernel now WARNs when only .ioctl is defined.

This is a move towards more explicit and fine-grained locking. Also note only changing the function signature and pointer will compile but will introduce the possibility of race conditions (two userspace apps doing ioctl calls at same time).