Re: Linux 2.4.1-ac15

From: Christoph Hellwig (hch@caldera.de)
Date: Mon Feb 19 2001 - 08:25:39 EST


In article <30512.982588558@ocs3.ocs-net> you wrote:
> No need for a callin routine, you can get this for free as part of
> normal scheduling. The sequence goes :-
>
> if (use_count == 0) {
> module_unregister();
> wait_for_at_least_one_schedule_on_every_cpu();
> if (use_count != 0) {
> module_register(); /* lost the unregister race */
> }
> else {
> /* nobody can enter the module now */
> module_release_resources();
> unlink_module_from_list();
> wait_for_at_least_one_schedule_on_every_cpu();
> free_module_storage();
> }
> }
>
> wait_for_at_least_one_schedule_on_every_cpu() prevents the next
> operation until at least one schedule has been executed on every cpu.
> Whether this is done as a call back or a separate kernel thread that
> schedules itself on every cpu or the current process scheduling itself
> on every cpu is an implementation detail. All that matters is that any
> other cpu that might have been accessing the module has gone through
> schedule and therefore is no longer accessing the module's data or
> code.

You just reinvented the read-copy-update model
(http://www.rdrop.com/users/paulmck/rclock/intro/rclock_intro.html)...

The mail proposing that locking model for module unloading is not yet
in the arvhices, sorry.

        Christoph

P.S. Weren't you Cc:'ed on that mail?

-- 
Of course it doesn't work. We've performed a software upgrade.
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This archive was generated by hypermail 2b29 : Fri Feb 23 2001 - 21:00:19 EST