Re: closefd: closes a file of any process

On Sat, Jun 24, 2000 at 11:01:43AM +0100, Tigran Aivazian wrote:
> On Fri, 23 Jun 2000, Manfred Spraul wrote:
> 
> > From: "Tigran Aivazian" <[e-mail]>
> > >
> > > So, I still think that at the moment there is NO (neither kernel nor
> > > userspace) way to close a given process' file descriptor. To do that one
> > > needs to (at least, there are lots of other issues!) enhance the lock
> > > subsystem to get rid of all references to 'current' context (used for
> > > deadlock avoidance detection, presumably).
> > 
> > I don't see the the deadlock, where is the problem?
> 
> the problem is not a deadlock but the fact that locking algorithms refer
> to 'current' explicitly - see the problem now?

At least in a 2.2.x kernel the only locks.c's function called from
filp_close is locks_remove_posix, and the only reference to current 
is in the call to locks_wake_up_blocks:

                if (wait) {
                        /* Let the blocked process remove waiter from the
                         * block list when it gets scheduled.
                         */
                        current->policy |= SCHED_YIELD;
                        schedule();
                } else {
                        /* Remove waiter from the block list, because by the
                         * time it wakes up blocker won't exist any more.
                         */
                        locks_delete_block(blocker, waiter);
                }

__but__ filp calls locs_wake_up_blocks __always__ with wait = 0

so it seems there is no a problem here

	Ulisses

                Debian/GNU Linux: a dream come true
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