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    SubjectRe: Please revert kobject_uevent UMH_NO_WAIT
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    On Thu, Apr 16, 2009 at 10:30 PM, Arjan van de Ven
    <arjan@linux.intel.com> wrote:
    > Greg KH wrote:
    >>
    >> On Thu, Apr 16, 2009 at 09:55:29PM +0100, Hugh Dickins wrote:
    >>>
    >>> Please revert commit f520360d93cdc37de5d972dac4bf3bdef6a7f6a7
    >>> "kobject: don't block for each kobject_uevent".
    >>>
    >>> Tetsuo Handa, running a kernel with CONFIG_DEBUG_PAGEALLOC=y
    >>> and CONFIG_UEVENT_HELPER_PATH=/sbin/hotplug, has been hitting RCU
    >>> detected CPU stalls: it's been spinning in the loop where do_execve()
    >>> counts up the args (but why wasn't fixup_exception working? dunno).
    >>>
    >>> The recent change, switching kobject_uevent_env() from UMH_WAIT_EXEC
    >>> to UMH_NO_WAIT, is broken: the exec uses args on the local stack here,
    >>> and an env which is kfreed as soon as call_usermodehelper() returns.
    >>> It very much needs to wait for the exec to be done.
    >>>
    >>> Or keep the UMH_NO_WAIT, and complicate the code to allocate and free
    >>> these resources correctly?  No, as GregKH pointed out when making the
    >>> commit, CONFIG_UEVENT_HELPER_PATH="" is a much better optimization -
    >>> though some distros are still saying /sbin/hotplug in their .config,
    >>> yet with no such binary in their initrd or their root.
    >>>
    >>> Or...
    >>>
    >>> [PATCH] revert kobject_uevent UMH_NO_WAIT
    >>>
    >>> Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
    >>> Signed-off-by: Hugh Dickins <hugh@veritas.com>
    >>
    >> Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
    >
    > Acked-by: Arjan van de Ven <arjan@linux.intel.com>
    > as well
    >
    > not worth the hassle if this breaks too much

    Acked-by: Will Newton <will.newton@gmail.com>

    It's causing crashes for me too (reported 10 days ago).

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