On Fri, Jul 02, 2010 at 11:06:37PM +0200, Oleg Nesterov wrote:

On 07/02, Peter Zijlstra wrote:

quoted

On Fri, 2010-07-02 at 11:01 -0700, Sridhar Samudrala wrote:

quoted

 Does  it (Tejun's kthread_clone() patch) also  inherit the
cgroup of the caller?

Of course, its a simple do_fork() which inherits everything just as you
would expect from a similar sys_clone()/sys_fork() call.

Yes. And I'm afraid it can inherit more than we want. IIUC, this is called
from ioctl(), right?

Then the new thread becomes the natural child of the caller, and it shares
->mm with the parent. And files, dup_fd() without CLONE_FS.

Signals. Say, if you send SIGKILL to this new thread, it can't sleep in
TASK_INTERRUPTIBLE or KILLABLE after that. And this SIGKILL can be sent
just because the parent gets SIGQUIT or abother coredumpable signal.
Or the new thread can recieve SIGSTOP via ^Z.

Perhaps this is OK, I do not know. Just to remind that kernel_thread()
is merely clone(CLONE_VM).

Oleg.

Right. Doing this might break things like flush.  The signal and exit
behaviour needs to be examined carefully. I am also unsure whether
using such threads might be more expensive than inheriting kthreadd.

-- 
MST