[PATCH][usercr]: Ghost tasks must be detached

Sukadev Bhattiprolu sukadev at linux.vnet.ibm.com
Wed Feb 9 11:02:16 PST 2011

Louis Rilling [Louis.Rilling at kerlabs.com] wrote:
| > | Are we still getting it with 2.6.37 ?
| > 
| > I am not currently getting the crash on 2.6.37 - I thought it was due to
| > the following commit which removed the check for task_detached() in
| > do_wait_thread().
| > 
| > 	commit 9cd80bbb07fcd6d4d037fad4297496d3b132ac6b
| > 	Author: Oleg Nesterov <oleg at redhat.com>
| > 	Date:   Thu Dec 17 15:27:15 2009 -0800
| I don't think that this introduced the bug. The bug triggers with EXIT_DEAD
| tasks, for which wait() must ignore (see below). So, the bug looks still there
| in 2.6.37.

Sorry, I did not mean to imply that the above commit caused the crash
you saw in Jun 2010.

I can reproduce a crash with 2.6.32 - where if container-init terminates
before a detached child, we get a crash when the detached child calls
proc_flush_mnt(). I suspected it was because do_wait_thread() skipped
over detached tasks (in 2.6.32).

The same test case does not crash on 2.6.37 - which includes the above commit.
The removes the check for detached tasks, my initial guess is that the above
commit, may have contributed to _fixing_ the crash in 2.6.37.


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