On Fri, 25 Jan 2013 09:58:42 -0300, Pablo Pessolani said:
My question is: Is there any know consequence if I enable preemption before copy_to_user/copy_from user (keeping the spinlock locked) and then disable preemption again after the copy?????
Well, at that point, you potentially have "a spinlock locked during operations that can be preempted", which you noted is "not recommended". The generic problem is that while you're spinning, you can get hit with a preempt, which ends up rescheduling or other fun stuff, and the preempting thread ends up calling into the same code - at which point you'll possibly deadlock because the second thread is now blocked on the spinlock that the first thread holds... You're much better off either restructuring your code so you don't do anything that can preempt, or fix your locking in other ways so the problem can't arise.