Messages in this thread | | | Date | Fri, 21 Dec 2007 22:31:34 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 4/4] usb: libusual: locking cleanup |
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On Fri, 21 Dec 2007 22:24:28 -0800 Pete Zaitcev <zaitcev@redhat.com> wrote:
> On Fri, 21 Dec 2007 00:00:04 -0800, Daniel Walker <dwalker@mvista.com> wrote: > > > I converted the usu_init_notify semaphore to normal mutex usage, and it > > should still prevent the request_module before the init routine is > > complete. Before it acted more like a complete, now the mutex protects > > two distinct section from running at the same time.. > > Let's see. > > > @@ -178,10 +179,7 @@ static int usu_probe_thread(void *arg) > > int rc; > > unsigned long flags; > > > > - /* A completion does not work here because it's counted. */ > > - down(&usu_init_notify); > > - up(&usu_init_notify); > > - > > + mutex_lock(&usu_probe_mutex); > > rc = request_module(bias_names[type]); > > When I tried it, usb-storage would not load with unresolved symbols. > It happens if child (usu_probe_thread) runs ahead of its parent > (usb_usual_init -> usb_register -> usu_probe). It's entirely possible, > depending on your scheduler.
afaict Daniel's change will fix that?
He releases usu_probe_mutex once the usb_register() has completed and this then allows the usb_probe_thread() to start working.
I'm still wondering if that theory has been tested though.
> I hate this down-up trick too
I'd be worried if you were proud of it ;)
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