Messages in this thread Patch in this message | | | Date | Thu, 16 Apr 2009 21:55:29 +0100 (BST) | From | Hugh Dickins <> | Subject | Please revert kobject_uevent UMH_NO_WAIT |
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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@i-love.sakura.ne.jp> Signed-off-by: Hugh Dickins <hugh@veritas.com> ---
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- 2.6.30-rc2/lib/kobject_uevent.c 2009-04-08 18:20:24.000000000 +0100 +++ linux/lib/kobject_uevent.c 2009-04-16 20:31:17.000000000 +0100 @@ -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:
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