Commit 05f54c13 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds

Revert "kobject: don't block for each kobject_uevent".

This reverts commit f520360d.

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.

An alternative would be to keep the UMH_NO_WAIT, and complicate the code
to allocate and free these resources correctly? but 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.
Reported-by: default avatarTetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
Acked-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Acked-by: default avatarWill Newton <will.newton@gmail.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 35c80d5f
......@@ -258,7 +258,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
goto exit;
retval = call_usermodehelper(argv[0], argv,
env->envp, UMH_NO_WAIT);
env->envp, UMH_WAIT_EXEC);
}
exit:
......
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