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    SubjectRe: [PATCH 2/7] ACPI / scan: Introduce common code for ACPI-based device hotplug
    Date
    On Wednesday, February 20, 2013 01:23:34 PM Toshi Kani wrote:
    > On Wed, 2013-02-20 at 14:23 +0100, Rafael J. Wysocki wrote:
    > > On Tuesday, February 19, 2013 03:43:08 PM Yasuaki Ishimatsu wrote:
    > :
    > > >
    > > > > - status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device, ej_event);
    > > > > - if (ACPI_FAILURE(status)) {
    > > > > - put_device(&acpi_device->dev);
    > > > > - kfree(ej_event);
    > > > > + acpi_evaluate_hotplug_ost(acpi_device->handle, ost_source,
    > > > > + ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
    > > > > + get_device(&acpi_device->dev);
    > > > > + ret = acpi_scan_hot_remove(acpi_device);
    > > >
    > > > Why don't you use acpi_os_hotplug_execute()? Do you have some reason?
    > >
    > > Yes, I do. acpi_eject_store() is run in a separate thread anyway (started by
    > > user space), so there's no need to use the workqueue for delayed execution here
    > > and we are under acpi_scan_lock anyway, so there shouldn't be any concurrency
    > > issues.
    >
    > Well, there is an issue... I just tested your patchset and hit the
    > following hang when I tried to delete a container through its sysfs
    > eject. This thread got stuck in trying to delete the sysfs eject file
    > of the container. I believe this is because the shell is still opening
    > this sysfs eject file.

    You're right.

    > PID: 1518 TASK: ffff88005f09c950 CPU: 1 COMMAND: "bash"
    > #0 [ffff88003392baf8] __schedule at ffffffff8151ba75
    > #1 [ffff88003392bb70] schedule at ffffffff8151bdc7
    > #2 [ffff88003392bb80] schedule_timeout at ffffffff8151aa55
    > #3 [ffff88003392bc00] wait_for_common at ffffffff8151bc43
    > #4 [ffff88003392bc70] wait_for_completion at ffffffff8151bd60
    > #5 [ffff88003392bc80] sysfs_addrm_finish at ffffffff811984ad
    > #6 [ffff88003392bcd0] sysfs_hash_and_remove at ffffffff81196deb
    > #7 [ffff88003392bd10] sysfs_remove_file at ffffffff81197051
    > #8 [ffff88003392bd40] device_remove_file at ffffffff81332950
    > #9 [ffff88003392bd50] acpi_device_unregister at ffffffff812a0556
    > #10 [ffff88003392bd80] acpi_bus_remove at ffffffff812a0658
    > #11 [ffff88003392bda0] acpi_bus_trim at ffffffff812a090e
    > #12 [ffff88003392bdd0] acpi_scan_hot_remove at ffffffff812a09c9
    > #13 [ffff88003392be30] acpi_eject_store at ffffffff812a0b45
    > #14 [ffff88003392be70] dev_attr_store at ffffffff81332038
    > #15 [ffff88003392be80] sysfs_write_file at ffffffff81197212
    > #16 [ffff88003392bee0] vfs_write at ffffffff8113a3cb
    > #17 [ffff88003392bf20] sys_write at ffffffff8113a5fd
    > #18 [ffff88003392bf80] system_call_fastpath at ffffffff81523759
    > RIP: 00000033a16e4950 RSP: 00007fff4a5f5368 RFLAGS: 00000206
    > RAX: 0000000000000001 RBX: ffffffff81523759 RCX: ffffffffffffffff
    > RDX: 0000000000000002 RSI: 00007f2f8a3d8000 RDI: 0000000000000001
    > RBP: 00007f2f8a3d8000 R8: 000000000000000a R9: 00007f2f8a3c4740
    > R10: 00007f2f8a3c4740 R11: 0000000000000246 R12: 00000033a19b1260
    > R13: 0000000000000002 R14: ffff880000000000 R15: ffff88003395d680
    > ORIG_RAX: 0000000000000001 CS: 0033 SS: 002b

    Well, admittedly, I didn't think about this situation.

    Since the eject attribute is under the device we're going to remove, the
    removal has to be done from a different thread (e.g. workqueue).

    OK, I'll fix up the patch.

    Thanks,
    Rafael


    --
    I speak only for myself.
    Rafael J. Wysocki, Intel Open Source Technology Center.


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