The patch titled revert "kobject: don't block for each kobject_uevent" has been removed from the -mm tree. Its filename was revert-kobject-dont-block-for-each-kobject_uevent.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: revert "kobject: don't block for each kobject_uevent" From: Hugh Dickins <hugh@xxxxxxxxxxx> Revert 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. Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Hugh Dickins <hugh@xxxxxxxxxxx> Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN lib/kobject_uevent.c~revert-kobject-dont-block-for-each-kobject_uevent lib/kobject_uevent.c --- a/lib/kobject_uevent.c~revert-kobject-dont-block-for-each-kobject_uevent +++ a/lib/kobject_uevent.c @@ -258,7 +258,7 @@ int kobject_uevent_env(struct kobject *k goto exit; retval = call_usermodehelper(argv[0], argv, - env->envp, UMH_NO_WAIT); + env->envp, UMH_WAIT_EXEC); } exit: _ Patches currently in -mm which might be from hugh@xxxxxxxxxxx are origin.patch clocksource-pass-clocksource-to-read-callback.patch mm-disable-preemption-in-apply_to_pte_range.patch getrusage-fill-ru_maxrss-value.patch prio_tree-debugging-patch.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html