Comment 9 for bug 708920

The following kernel stack was captured on a system in "fork() hangs" state via "echo t > /proc/sysrq-trigger". The code for libctest is here: https://gist.github.com/2d2b78987ea451c2edd6

<6>[853486.204130] libctest R running task 0 13658 1417 0x00000000
<4>[853486.204132] ffffffff00000000 0000000000000000 ffff88088b03a980 ffff8800e3489ea8
<4>[853486.204134] ffffffff810909f7 ffff88088b03aa48 ffff88088b03a980 ffff8800e3489ec8
<4>[853486.204137] ffffffff81109f04 ffff880889a27c80 0000000000008002 ffff8804d4470680
<4>[853486.204139] Call Trace:
<4>[853486.204141] [<ffffffff810909f7>] ? __call_rcu+0x77/0x1c0
<4>[853486.204143] [<ffffffff81109f04>] ? mntput_no_expire+0x24/0x110
<4>[853486.204145] [<ffffffff811078ab>] ? alloc_fd+0x4b/0x160
<4>[853486.204148] [<ffffffff810f79f0>] ? putname+0x30/0x50
<4>[853486.204150] [<ffffffff810eb526>] ? do_sys_open+0x106/0x160
<4>[853486.204152] [<ffffffff810eb5ab>] ? sys_open+0x1b/0x20
<4>[853486.204154] [<ffffffff81009ba8>] ? system_call_fastpath+0x16/0x1b
<4>[853486.204157] [<ffffffff81009b40>] ? system_call+0x0/0x52
<4>[853486.204159] [<ffffffff81009b40>] ? system_call+0x0/0x52