Ingo Molnar wrote:
* Paulo Marques <[EMAIL PROTECTED]> wrote:
looking at the problem from another angle: wouldnt this be something
that would benefit from freeze_processes()/unfreeze_processes(), and
hence no locking would be required?
I also considered this, but it seemed a little too "blunt" to stop
everything (including completely unrelated processes and kernel
threads) just to remove a module.
'just to remove a module' is very, very rare, on the timescale of most
kernel ops. Almost no distro does it. Furthermore, because we want to do
CPU-hotplug that way, we really want to make
freeze_processes()/unfreeze_processes() 'instantaneous' to the human -
and it is that already. (if it isnt in some case we can make it so)
Ok. I started to look at this approach and realized that module.c
already does this:
....
static int __unlink_module(void *_mod)
{
struct module *mod = _mod;
list_del(&mod->list);
return 0;
}
/* Free a module, remove from lists, etc (must hold module mutex). */
static void free_module(struct module *mod)
{
/* Delete from various lists */
stop_machine_run(__unlink_module, mod, NR_CPUS);
....
However stop_machine_run doesn't seem like the right thing to do,
because users of the "modules" list don't seem to do anything to prevent
preemption. Am I missing something?
Does freeze_processes() / unfreeze_processes() solve this by only
freezing processes that have voluntarily scheduled (opposed to just
being preempted)?
--
Paulo Marques - www.grupopie.com
"The Computer made me do it."
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