Trying to build a kernel on a 48 core x86_64 box using make -j 64 and
I'm exploding in the scheduler.  I'm running (and building) kernel
f7b84a6ba7eaeba4e1df8feddca1473a7db369a5  There are three distinct
signatures of problems.  Some boots I'll see all 3 of these failures
sometimes only 1 or 2 of them.  That's the reason they are kinda split
up in dmesg.

1) gcc/3141 is trying to acquire lock:
 (&(&sem->wait_lock)->rlock){......}, at: [<ffffffff81223234>] __down_read_trylock+0x13/0x46

but task is already holding lock:
 (&rq->lock){-.-.-.}, at: [<ffffffff8103dd2d>] task_rq_lock+0x51/0x83

2) WARN() in kernel/sched_fair.c:1001 hrtick_start_fair()

3) NULL pointer dereference at 0000000000000168 in check_preempt_wakeup
      kernel/sched_fair.c

Full backtraces are in the attached dmesg.