On Wednesday 24 February 2010, Moore, Robert wrote: > > Rafael, > > I've got some issues with this design. > > First of all, are the two interfaces, acpi_remove_notify_handler() and > acpi_remove_gpe_handler(), really being used in such a way to require such > synchronization? I had a problem with that when I was trying to implement adding more than one system notify handler per device at the PCI level. Specifically, I was trying to create an extra layer of notify objects to be used by the PCI layer for installing ACPI system notify handlers such that every PCI device had one handler that might handle wakeup notifications as well as hotplug notifications. That didn't work, because I needed to remove a notify object from memory after calling acpi_remove_notify_handler() for the handler associated with it and I was unable to tell whether that was safe. The patch at http://patchwork.kernel.org/patch/80104/ solved this issue for me (BTW, you told me you'd have a look at this one :-)), but I think it generally is good to know a handler is not being executed after acpi_remove_notify_handler() or acpi_remove_gpe_handler() has been called for it. > Is there any way to limit their use to times where it is known that no > handlers will be executing? I don't think this is generally possible. Since the event handlers are called from a workqueue, we can't really guarantee any synchronization between them and the other threads unless we use a mechanism that will enforce it. > In addition, I'm afraid that this whole "events" mechanism, with an interface > to wait for event completion, and now the concept of adding "barriers" to the > event queue, is much too OS-specific for the core ACPICA code. OK, I'm not going to insist. However, I think that acpi_os_wait_events_complete() should be called before we try to acquire ACPI_MTX_EVENTS for the first time, because dropping it "temporarily" just in order to call acpi_os_wait_events_complete() really defeats the purpose of the locking. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
