On 03/30, Oleg Nesterov wrote: > > On 03/29, Al Viro wrote: > > > > On Sun, Mar 29, 2009 at 11:36:35PM +0200, Oleg Nesterov wrote: > > > > ... or just do that to fs_struct. After finding that there's no outside > > > > users. Commenst? > > > > > > This is even worse. Not only we race with our sub-threads, we race > > > with CLONE_FS processes. > > > > > > We can't mark fs_struct after finding that there's no outside users > > > lockless. Because we can't know whether this is "after" or not, we > > > can't trust "atomic_read(fs->count) <= n_fs". > > > > We can lock fs_struct in question, go through the threads, then mark > > or bail out. With cloning a reference to fs_struct protected by the > > same lock. > > Yes, this is what I meant, copy_fs() needs this lock too, > > > FWIW, I'm not at all sure that we want atomic_t for refcount in that > > case... > > I think you are right, because exit_fs() should take fs->lock as well. > > But, again. What whould we do when check_unsafe_exec() takes fs->lock > and sees that this ->fs is already marked? Ah, I am stupid. There is no another process if this flag is set. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
