On Thu, May 19, 2016 at 03:30:32PM +0200, Pali Rohár wrote: > On Monday 25 April 2016 22:06:11 Gabriele Mazzotta wrote: > > 2016-04-18 14:35 GMT+02:00 Pali Rohár <pali.rohar@xxxxxxxxx>: > > > On Tuesday 29 March 2016 15:11:35 Rafael J. Wysocki wrote: > > >> On Monday, March 28, 2016 10:33:09 AM Darren Hart wrote: > > >> > On Thu, Mar 24, 2016 at 12:24:56PM +0100, Gabriele Mazzotta wrote: > > >> > > 2016-03-24 10:39 GMT+01:00 Pali Rohár <pali.rohar@xxxxxxxxx>: > > >> > > > On Monday 21 March 2016 16:13:34 Gabriele Mazzotta wrote: > > >> > > >> 2016-03-21 13:17 GMT+01:00 Pali Rohár <pali.rohar@xxxxxxxxx>: > > >> > > >> > On Friday 18 March 2016 23:44:23 Gabriele Mazzotta wrote: > > >> > > >> >> +#ifdef CONFIG_PM_SLEEP > > >> > > >> >> +static void ACPI_SYSTEM_XFACE rbtn_acpi_clear_flag(void *context) > > >> > > >> >> +{ > > >> > > >> >> + struct rbtn_data *rbtn_data = context; > > >> > > >> >> + > > >> > > >> >> + rbtn_data->suspended = false; > > >> > > >> >> +} > > >> > > >> >> + > > >> > > >> >> +static int rbtn_suspend(struct device *dev) > > >> > > >> >> +{ > > >> > > >> >> + struct acpi_device *device = to_acpi_device(dev); > > >> > > >> >> + struct rbtn_data *rbtn_data = acpi_driver_data(device); > > >> > > >> >> + > > >> > > >> >> + rbtn_data->suspended = true; > > >> > > >> >> + > > >> > > >> >> + return 0; > > >> > > >> >> +} > > >> > > >> >> + > > >> > > >> >> +static int rbtn_resume(struct device *dev) > > >> > > >> >> +{ > > >> > > >> >> + struct acpi_device *device = to_acpi_device(dev); > > >> > > >> >> + struct rbtn_data *rbtn_data = acpi_driver_data(device); > > >> > > >> >> + acpi_status status; > > >> > > >> >> + > > >> > > >> >> + /* > > >> > > >> >> + * Clear the flag only after we received the extra > > >> > > >> >> + * ACPI notification. > > >> > > >> >> + */ > > >> > > >> >> + status = acpi_os_execute(OSL_NOTIFY_HANDLER, > > >> > > >> >> + rbtn_acpi_clear_flag, rbtn_data); > > >> > > >> >> + if (ACPI_FAILURE(status)) > > >> > > >> >> + rbtn_data->suspended = false; > > >> > > >> > > > >> > > >> > I case when acpi_os_execute success it calls rbtn_acpi_clear_flag, > > >> > > >> > right? And that will set suspended to false. When acpi_os_execute fails, > > >> > > >> > then it set suspended too to false... Then whole acpi_os_execute doing > > >> > > >> > just "barrier" after which suspended flag can be set to false. So I > > >> > > >> > think rbtn_acpi_clear_flag function is not needed here. > > >> > > >> > > > >> > > >> > Cannot you pass NULL or empty function pointer as callback? Or what was > > >> > > >> > reason to do that flag clearing at "two places"? > > >> > > >> > > >> > > >> acpi_os_execute doesn't wait for the callback to be executed, so > > >> > > >> I can't clear the flag from rbtn_resume. > > >> > > > > > >> > > > acpi_os_execute calls callback asynchronously later? Or what exactly do it? > > >> > > > > >> > > In this case, it adds the callback to the kacpi_notify_wq workqueue > > >> > > for deferred execution. > > >> > > > >> > +Rafael for context/advice on the use of acpi_os_execute here. > > >> > > > >> > This is true, but a quick scan through that call path doesn't tell me why we > > >> > would need to call it here instead of just setting rbtn_data->suspended = false. > > >> > The comment suggests waiting for the event, but is that what this is doing? It > > >> > appears to me to be immediately scheduling the function to a work queue, not > > >> > waiting for the event notifier. > > >> > > >> I think this is supposed to work as a barrier. That is, it will only run after > > >> all events in the queue have been processed. > > >> > > >> I'm not sure if that's necessary, though. > > >> > > >> Thanks, > > >> Rafael > > >> > > > > > > Darren, Gabriele, what is state of this patch? Bug is not still fixed, > > > right? > > > > Yes, the bug is still there and this patch fixes it. > > > > Just to make it clear, we need the barrier. Andrei could reproduce > > the bug without it [1], but not with it, as he confirmed in this > > thread [2]. > > > > [1] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8001 > > [2] http://article.gmane.org/gmane.linux.drivers.platform.x86.devel/8937 > > Ok, so it means that somebody (who understand ACPI) should review code > and accept it or show what is needed to fix. Plus maybe adds more > comments how that "barrier" works as I was first confused... > > Darren, Rafael, can you do review of this patch? > Pali and Gabriele have responded to all questions raised. I have some reservations that this solution is still a bit racy, but it does fix the problem for the affected users. I've queued this. Thanks for your patience. -- Darren Hart Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html