Re: [RFC] Race condition?

[Dave Hansen]

Oliver Neukum wrote:
> Am Freitag, 2. August 2002 15:46 schrieb Kasper Dupont:
> 
>>Is there a race condition in this piece of code from do_fork in
> 
> It would seem so. Perhaps the BKL was taken previously.
> 

Even if it was, I doubt the code ever knowingly relied upon it.  If I 
know that I'm protected under a lock, I rarely go to the trouble of 
atomic operations.

The root of the problem is that the reference count is being relied on 
for the wrong thing.  There is a race on p->user between the
dup_task_struct() and whenever the atomic_inc(&p->user->__count) 
occcurs.   The user reference count needs to be incremented in 
dup_task_struct(), before the copy occurs.
-- 
Dave Hansen
[e-mail]