The patch titled
revert "kobject: don't block for each kobject_uevent"
has been added to the -mm tree. Its filename is
revert-kobject-dont-block-for-each-kobject_uevent.patch
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------------------------------------------------------
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
revert-kobject-dont-block-for-each-kobject_uevent.patch
mm-pass-correct-mm-when-growing-stack.patch
mm-disable-preemption-in-apply_to_pte_range.patch
getrusage-fill-ru_maxrss-value.patch
prio_tree-debugging-patch.patch
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