Re: Please revert kobject_uevent UMH_NO_WAIT

[Arjan van de Ven]

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@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx>
>
> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

Acked-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
as well

not worth the hassle if this breaks too much
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