• Jean Delvare's avatar
    platform: reorder platform_device_del · dc4c15d4
    Jean Delvare authored
    In platform_device_del(), we currently delete the device resources
    first, then we delete the device itself. This causes a (minor) bug to
    occur when one unregisters a platform device before unregistering its
    platform driver, and the driver is requesting (in .probe()) and
    releasing (in .remove()) a resource of the device. The device
    resources are already gone by the time the driver gets the chance to
    release the resources it had been requesting, causing an error like:
    Trying to free nonexistent resource <0000000000000295-0000000000000296>
    
    If the platform driver is unregistered first, the problem doesn't
    occur, as the driver will have the opportunity to release the
    resources it had requested before the device resources themselves are
    released. It's a bit odd that unregistering the driver first or the
    device first doesn't lead to the same result.
    
    So I believe that we should delete the device first in
    platform_device_del(). I've searched the git history and found that it
    used to be the case before 2.6.8, but was changed here:
    
    http://www.kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commitdiff;h=96ef7b3689936ee1e64b711511342026a8ce459c
    
    > 2004/07/14 16:09:44-07:00 dtor_core
    > [PATCH] Driver core: Fix OOPS in device_platform_unregister
    > 
    > Driver core: platform_device_unregister should release resources first
    >              and only then call device_unregister, otherwise if there
    >              are no more references to the device it will be freed and
    >              the fucntion will try to access freed memory.  
    
    However we now have an explicit call to put_device() at the end of
    platform_device_unregister() so I guess the original problem no longer
    exists and it is safe to revert that change.
    Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    dc4c15d4
platform.c 16.7 KB