Revert "sched, autogroup: Stop going ahead if autogroup is disabled"

This reverts commit 800d4d30c8f20bd728e5741a3b77c4859a613f7c.

Between commits 8323f26ce342 ("sched: Fix race in task_group()") and
800d4d30c8f2 ("sched, autogroup: Stop going ahead if autogroup is
disabled"), autogroup is a wreck.

With both applied, all you have to do to crash a box is disable
autogroup during boot up, then reboot..  boom, NULL pointer dereference
due to commit 800d4d30c8f2 not allowing autogroup to move things, and
commit 8323f26ce342 making that the only way to switch runqueues:

  BUG: unable to handle kernel NULL pointer dereference at           (null)
  IP: [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90
  Pid: 7047, comm: systemd-user-se Not tainted 3.6.8-smp #7 MEDIONPC MS-7502/MS-7502
  RIP: effective_load.isra.43+0x50/0x90
  Process systemd-user-se (pid: 7047, threadinfo ffff880221dde000, task ffff88022618b3a0)
  Call Trace:
    select_task_rq_fair+0x255/0x780
    try_to_wake_up+0x156/0x2c0
    wake_up_state+0xb/0x10
    signal_wake_up+0x28/0x40
    complete_signal+0x1d6/0x250
    __send_signal+0x170/0x310
    send_signal+0x40/0x80
    do_send_sig_info+0x47/0x90
    group_send_sig_info+0x4a/0x70
    kill_pid_info+0x3a/0x60
    sys_kill+0x97/0x1a0
    ? vfs_read+0x120/0x160
    ? sys_read+0x45/0x90
    system_call_fastpath+0x16/0x1b
  Code: 49 0f af 41 50 31 d2 49 f7 f0 48 83 f8 01 48 0f 46 c6 48 2b 07 48 8b bf 40 01 00 00 48 85 ff 74 3a 45 31 c0 48 8b 8f 50 01 00 00 <48> 8b 11 4c 8b 89 80 00 00 00 49 89 d2 48 01 d0 45 8b 59 58 4c
  RIP  [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90
   RSP <ffff880221ddfbd8>
  CR2: 0000000000000000

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org # 2.6.39+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+ testing: "workqueue: convert BUG_ON()s in __queue_delayed_work() to WARN_ON_ONCE()s" - https://github.com/torvalds/linux/commit/fc4b514f2727f74a4587c31db87e0e93465518c3
linux/kernel.h: define SYMBOL_PREFIX

Define SYMBOL_PREFIX to be the same as CONFIG_SYMBOL_PREFIX if set by
the architecture, or "" otherwise. This avoids the need for ugly #ifdefs
whenever symbols are referenced in asm blocks.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
tcp: fix crashes in do_tcp_sendpages()

Recent network changes allowed high order pages being used
for skb fragments.

This uncovered a bug in do_tcp_sendpages() which was assuming its caller
provided an array of order-0 page pointers.

We only have to deal with a single page in this function, and its order
is irrelevant.

Reported-by: Willy Tarreau <w@1wt.eu>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Conflicts:
	net/ipv4/tcp.c