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Revert "sched, autogroup: Stop going ahead if autogroup is disabled"
This reverts commit800d4d30c8
. Between commits8323f26ce3
("sched: Fix race in task_group()") and800d4d30c8
("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 commit800d4d30c8
not allowing autogroup to move things, and commit8323f26ce3
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>
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parent
d3594ea2b3
commit
fd8ef11730
@ -143,15 +143,11 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
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p->signal->autogroup = autogroup_kref_get(ag);
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if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
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goto out;
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t = p;
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do {
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sched_move_task(t);
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} while_each_thread(p, t);
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out:
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unlock_task_sighand(p, &flags);
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autogroup_kref_put(prev);
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}
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@ -4,11 +4,6 @@
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#include <linux/rwsem.h>
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struct autogroup {
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/*
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* reference doesn't mean how many thread attach to this
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* autogroup now. It just stands for the number of task
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* could use this autogroup.
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*/
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struct kref kref;
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struct task_group *tg;
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struct rw_semaphore lock;
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