From: Hugh Dickins Date: Thu, 16 Apr 2009 20:55:29 +0000 (+0100) Subject: Revert "kobject: don't block for each kobject_uevent". X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=05f54c13cd0c;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git Revert "kobject: don't block for each kobject_uevent". This reverts commit f520360d93cdc37de5d972dac4bf3bdef6a7f6a7. 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: Tetsuo Handa Signed-off-by: Hugh Dickins Acked-by: Greg Kroah-Hartman Acked-by: Arjan van de Ven Acked-by: Will Newton Signed-off-by: Linus Torvalds --- diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 97a777ad4f59..dafeecf5b143 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -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: