• LongX Zhang's avatar
    driver core / PM: move the calling to device_pm_remove behind the calling to bus_remove_device · 4b6d1f12
    LongX Zhang authored
    We hit an hang issue when removing a mmc device on Medfield Android phone by sysfs interface.
    
    device_pm_remove will call pm_runtime_remove which would disable
    runtime PM of the device. After that pm_runtime_get* or
    pm_runtime_put* will be ignored. So if we disable the runtime PM
    before device really be removed, drivers' _remove callback may
    access HW even pm_runtime_get* fails. That is bad.
    
    Consider below call sequence when removing a device:
    device_del => device_pm_remove
                 => class_intf->remove_dev(dev, class_intf)  => pm_runtime_get_sync/put_sync
                 => bus_remove_device => device_release_driver => pm_runtime_get_sync/put_sync
    
    remove_dev might call pm_runtime_get_sync/put_sync.
    Then, generic device_release_driver also calls pm_runtime_get_sync/put_sync.
    Since device_del => device_pm_remove firstly, later _get_sync wouldn't really wake up the device.
    
    I git log -p to find the patch which moves the calling to device_pm_remove ahead.
    It's below patch:
    
    commit  775b64d2
    Author: Rafael J. Wysocki <rjw@sisk.pl>
    Date:   Sat Jan 12 20:40:46 2008 +0100
    
         PM: Acquire device locks on suspend
    
         This patch reorganizes the way suspend and resume notifications are
         sent to drivers.  The major changes are that now the PM core acquires
         every device semaphore before calling the methods, and calls to
         device_add() during suspends will fail, while calls to device_del()
         during suspends will block.
    
         It also provides a way to safely remove a suspended device with the
         help of the PM core, by using the device_pm_schedule_removal() callback
         introduced specifically for this purpose, and updates two drivers (msr
         and cpuid) that need to use it.
    
    As device_pm_schedule_removal is deleted by another patch, we need also revert other parts of the patch,
    i.e. move the calling of device_pm_remove after the calling to bus_remove_device.
    Signed-off-by: default avatarLongX Zhang <longx.zhang@intel.com>
    Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    4b6d1f12
core.c 50.7 KB