Re: Adding pulse support to gpio(4), gpioctl(8)

[Marc Balmer <mbalmer%NetBSD.org@localhost>]

Am 24.08.11 04:50, schrieb Mouse:
>>> Well, you need to open it first, before you can to ioctl, and if
>>> only one process can open it, only one process can ioctl it, right?
>> Wrong.
> 
> Agreed.
> 
>> Multiple threads can ioctl and nobody prevents one from having a
>> single process with multiple threads (pthreads, if you like).
> 
> Not only that, but even without threading, there are at least two ways
> I can think of offhand that a file descriptor, once opened, can end up
> in multiple processes' open file tables: fork() and SCM_RIGHTS.  (There
> are probably others, too.)

What can be done about this?  Do any drivers protect themselves against
the situation where after a fork() the parent and the child process can
access the file descriptor without causing mayhem?

What is the best way, or common practive to make driver really mpsafe?