Messages in this thread | | | Date | Thu, 26 Dec 2013 11:53:10 +0900 | From | Yasuaki Ishimatsu <> | Subject | Re: [PATCH 7/10] ACPI / hotplug: Move container-specific code out of the core |
| |
HI Rafael,
(2013/12/26 10:01), Rafael J. Wysocki wrote: > On Monday, December 23, 2013 02:58:38 PM Rafael J. Wysocki wrote: >> On Saturday, December 14, 2013 06:07:06 AM Rafael J. Wysocki wrote: >>> On Friday, December 13, 2013 02:17:32 PM Yasuaki Ishimatsu wrote: >>>> (2013/12/13 13:56), Rafael J. Wysocki wrote: >>>>> On Friday, December 13, 2013 11:56:32 AM Yasuaki Ishimatsu wrote: >>>>>> Hi Rafael, >>>>> >>>>> Hi, >>>>> >>>>>> Please share your more detailed idea. I started to implement the following >>>>>> idea. But the idea has one problem. >>>>>> >>>>>>>>> The eject work flow can be: >>>>>>>>> (1) an eject event occurs, >>>>>>>>> (2) the container "physical" device fails offline in acpi_scan_hot_remove() >>>>>>>>> emmitting, say, KOBJ_CHANGE for the "physical" device, >>>>>>>>> (3) user space notices the KOBJ_CHANGE and does the cleanup as needed, >>>>>>>>> (4) user space changes the "physical" container device flag controlling >>>>>>>>> offline to 0, >>>>>>>>> (5) user space uses the sysfs "eject" attribute of the ACPI container object >>>>>>>>> to finally eject the container, >>>>>>>>> (6) the offline in acpi_scan_hot_remove() is now successful, because the >>>>>>>>> flag controlling it has been set to 0 in step (4), >>>>>>>>> (7) the "physical" container device goes away before executing _EJ0, >>>>>>>>> (8) the container is ejected. >>>>>> >>>>>> I want to emit KOBJ_CHANGE before offlining devices on container device at (2). >>>>>> But acpi_scan_hot_remove() offlines devices on container device at first. >>>>>> So when offline container device, devices on container has been offlined. >>>>>> >>>>>> Thus the idea cannot fulfill my necessary feature. >>>>> >>>>> Well, in that case we need to treat containers in a special way at the ACPI >>>>> level. Which is a bit unfortunate so to speak. >>>>> >>>>> To that end I'd try to add a new flag to struct acpi_hotplug_profile, say >>>>> .verify_offline, such that if set, it would cause acpi_scan_hot_remove() to >>>>> check if all of the "physical" companions of the top-level device are offline >>>>> to start with, and if not, it would just emit KOBJ_CHANGE for the companions >>>>> that are not offline and bail out. >>>>> >>>>> So the above algorithm would become: >>>>> >>>>> (1) an eject event occurs, >>>>> (2) acpi_scan_hot_remove() checks the verify_offline flag in the target device's >>>>> scan_handler structure, >>>>> (3) if set (it would always be set for containers), acpi_scan_hot_remove() >>>>> checks the status of the target device's "physical" companions; if at least >>>>> one of them is offline, KOBJ_CHANGE is emitted for that "physical" device, >>>>> and acpi_scan_hot_remove() returns, [I guess we can just emit KOBJ_CHANGE >>>>> for the first companion that is not offline at this point.] >>>>> (4) user space notices the KOBJ_CHANGE and does the cleanup as needed; in the >>>>> process it carries out the offline operation for the container's "physical" >>>>> companion (there's only one such companion for each container), [That >>>>> operation for the container itself is trivial, but to succeed it requires >>>>> all devices below the container to be taken offline in advance.] >>>>> (5) user space uses the sysfs "eject" attribute of the ACPI container object >>>>> to finally eject the container, >>>>> (6) acpi_scan_hot_remove() is now successful, because the container's "physical" >>>>> companion is now offline, >>>>> (7) the "physical" container device goes away before executing _EJ0, >>>>> (8) the container is ejected. >>>>> >>>>> I think that should work for you. >>>> >>>> This idea seems to same as your previous work. >>>> http://lkml.org/lkml/2013/2/23/97 >>> >>> No, it is not. That one didn't involve physical device representations. >>> >>>> How about add autoremove flag into acpi_hotplug_profile and check it as follow: >>> >>> This is very similar to "enable" except that it generates the uevent and >>> "enable" doesn't. You might as well modify "enable" to trigger a uevent if >>> eject is not enabled (note that with the latest patches in linux-next "enable" >>> only applies to eject). >>> >>> That said I don't think we should generate any uevents for struct acpi_device >>> objects, because they are not devices. >>> >>>> --- >>>> drivers/acpi/scan.c | 5 +++++ >>>> 1 file changed, 5 insertions(+) >>>> >>>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c >>>> index 5383c81..c43d110 100644 >>>> --- a/drivers/acpi/scan.c >>>> +++ b/drivers/acpi/scan.c >>>> @@ -409,6 +409,11 @@ static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data) >>>> ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED; >>>> goto err_out; >>>> } >>>> + if (!handler->hotplug.autoremove) { >>>> + kobject_uevent(&device->dev.kobj, KOBJ_CHANGE); >>>> + ost_code = ACPI_OST_SC_EJECT_NON_SPECIFIC_FAILURE; >>>> + goto err_out; >>>> + } >>>> acpi_evaluate_hotplug_ost(handle, ACPI_NOTIFY_EJECT_REQUEST, >>>> ACPI_OST_SC_EJECT_IN_PROGRESS, NULL); >>>> break; >>>> >>>> Adding the check into "acpi_hotplug_notify_cb()", user need not change the >>>> flag for removing container device by "sysfs eject". >>> >>> Which is utterly confusing. There is no reason whatsoever why the sysfs eject >>> attribute should work differently from the event-triggered eject. Quite the >>> opposite is the case: it should work in the same way in my opinion so that it >>> is possible to test the eject code path using that attribute. >>> >>> I'm traveling now, but when I get back home (next week), I'll try to implement >>> the thing I was talking about above. >> >> It took some more time than I had expected, but I finally was able to get to that. >> >> The following two patches implement the idea. This is the minimum (in my opinion) >> implementation and it may be extended in some ways. >> >> Patch [1/2] introduces a new demand_offline flag for struct acpi_hotplug_profile >> that makes acpi_scan_hot_remove() check the offline status of the device object's >> companion physical devices to start with and return -EBUSY if at least one of them >> is not offline. >> >> Patch [2/2] uses that flag to implement the container handling. The details are >> in the changelog, but that's how it is supposed to work. >> >> During the initial namespace scan the container ACPI scan handler should create >> "physical" system container device under /sys/devices/system/container/ for >> each ACPI container object (the sysfs name of that device should be the same as >> the sysfs name of the corresponding container object and they should be linked >> to each other via the firmware_node and physical_node symbolic links, respectively). >> Those system container devices are initially online. >> >> When a container eject event happens, acpi_scan_hot_remove() will notice that >> hotplug.demand_offline is set in the device object's scan handler and will >> check the online status of its "physical" companion device, which is online >> (that is the system container device the above paragraph is about). That will >> cause KOBJ_CHANGE to be emitted for the system container device and -EBUSY to >> be returned by acpi_scan_hot_remove(). >> >> Now, user space needs to offline the system container device through its online >> sysfs attribute (that should be present, because the bus type for containers >> provides the online and offline callbacks). However, the offline for system >> container devices will only succeed if the physical devices right below the >> container are all offline, so user space will have to offline those devices >> before attempting to offline the system container device itself. When >> finished, user space can trigger the container removal with the help of the >> eject sysfs attribute of the ACPI container object pointed to by the system >> container device's firmware_node link (this time the check in >> acpi_scan_hot_remove() will succeed, because the system container device in >> question is now offline). >> >> The way it is implemented is a bit hackish (the driver_data pointer is slightly >> abused), but that's a special case and I wanted to avoid adding new fields to >> struct device just for handling it. >> >> The patches haven't been tested yet. I'm going to do that later today, but >> first I need to take care of some other things, so that has to wait. >
Thank you for implementing your idea.
> The series of the two patches: > > [1/2] ACPI / hotplug: Add demand_offline hotplug profile flag > https://patchwork.kernel.org/patch/3396711/ > > [2/2] ACPI / hotplug / driver core: Handle containers in a special way > https://patchwork.kernel.org/patch/3399081/ > > has been tested now and seems to work as expected, at least for a container > that has no children (that's one I could simulate easily in a meaningful way). > > For this reason, if there are no objections, I'll resend them as an official > submission during the next couple of days.
I'm testing these patches now. If I have a comment, I send it to these threads.
Thanks, Yasuaki Ishimatsu
> > Thanks! >
| |