FYI, we noticed the below changes on

commit eeb61e53ea19be0c4015b00b2e8b3b2185436f2b ("sched: Fix race between task_group and sched_task_group")


+---------------------------+------------+------------+
|                           | xfs-for-li | eeb61e53ea |
+---------------------------+------------+------------+
| boot_successes            | 0          | 0          |
| boot_failures             | 54         | 10         |
| BUG:kernel_boot_hang      | 54         | 10         |
| INFO:suspicious_RCU_usage | 0          | 10         |
| backtrace:do_fork         | 0          | 10         |
+---------------------------+------------+------------+


[    0.054010] ftrace: allocating 44163 entries in 87 pages
[    0.072399] 
[    0.073480] ===============================
[    0.074916] [ INFO: suspicious RCU usage. ]
[    0.076000] 3.18.0-rc2-g05da589 #861 Not tainted
[    0.076000] -------------------------------
[    0.076000] kernel/sched/core.c:7449 suspicious rcu_dereference_check() usage!
[    0.076000] 
[    0.076000] other info that might help us debug this:
[    0.076000] 
[    0.076000] 
[    0.076000] rcu_scheduler_active = 1, debug_locks = 0
[    0.076000] 2 locks held by swapper/0/0:
[    0.076000]  #0:  (&p->pi_lock){......}, at: [<c1069318>] task_rq_lock+0x28/0xba
[    0.076000]  #1:  (&rq->lock){-.....}, at: [<c1069336>] task_rq_lock+0x46/0xba
[    0.076000] 
[    0.076000] stack backtrace:
[    0.076000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.18.0-rc2-g05da589 #861
[    0.076000] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    0.076000]  00000000 00000000 c209be98 c1b238b0 00000001 c209beb4 c108ba6a c1f54e96
[    0.076000]  c20a3550 d30c0000 d370c300 c20b28a0 c209bed4 c10731b6 00000000 00003550
[    0.076000]  00200246 d30c0000 00000000 00000000 c209bedc c1073285 c209bef0 c10cb273
[    0.076000] Call Trace:
[    0.076000]  [<c1b238b0>] dump_stack+0x48/0x60
[    0.076000]  [<c108ba6a>] lockdep_rcu_suspicious+0xd3/0xdc
[    0.076000]  [<c10731b6>] sched_move_task+0xd1/0x17c
[    0.076000]  [<c1073285>] cpu_cgroup_fork+0xd/0xf
[    0.076000]  [<c10cb273>] cgroup_post_fork+0xe1/0xec
[    0.076000]  [<c10464a4>] copy_process+0x1652/0x181f
[    0.076000]  [<c1b1c321>] ? rest_init+0x116/0x116
[    0.076000]  [<c1073f5b>] ? sched_clock_cpu+0x11b/0x136
[    0.076000]  [<c1b1c321>] ? rest_init+0x116/0x116
[    0.076000]  [<c10467c7>] do_fork+0x7d/0x632
[    0.076000]  [<c1088ad7>] ? trace_hardirqs_on_caller+0x160/0x17b
[    0.076000]  [<c1b1c321>] ? rest_init+0x116/0x116
[    0.076000]  [<c1088afd>] ? trace_hardirqs_on+0xb/0xd
[    0.076000]  [<c106ce9c>] ? nr_context_switches+0xb2/0xe4
[    0.076000]  [<c1b1c321>] ? rest_init+0x116/0x116
[    0.076000]  [<c1046d9b>] kernel_thread+0x1f/0x24
[    0.076000]  [<c1b1c22a>] rest_init+0x1f/0x116
[    0.076000]  [<c222db5b>] start_kernel+0x3fd/0x404
[    0.076000]  [<c222d2af>] i386_start_kernel+0x79/0x7d
[    0.076113] Getting VERSION: 50014
[    0.077525] Getting VERSION: 50014
[    0.080016] Getting ID: 0



	--yliu