fd8ef11730
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 commit800d4d30c8not allowing autogroup to move things, and commit8323f26ce3making 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>
60 lines
1.3 KiB
C
60 lines
1.3 KiB
C
#ifdef CONFIG_SCHED_AUTOGROUP
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#include <linux/kref.h>
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#include <linux/rwsem.h>
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struct autogroup {
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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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unsigned long id;
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int nice;
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};
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extern void autogroup_init(struct task_struct *init_task);
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extern void autogroup_free(struct task_group *tg);
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static inline bool task_group_is_autogroup(struct task_group *tg)
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{
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return !!tg->autogroup;
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}
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extern bool task_wants_autogroup(struct task_struct *p, struct task_group *tg);
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static inline struct task_group *
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autogroup_task_group(struct task_struct *p, struct task_group *tg)
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{
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int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
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if (enabled && task_wants_autogroup(p, tg))
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return p->signal->autogroup->tg;
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return tg;
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}
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extern int autogroup_path(struct task_group *tg, char *buf, int buflen);
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#else /* !CONFIG_SCHED_AUTOGROUP */
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static inline void autogroup_init(struct task_struct *init_task) { }
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static inline void autogroup_free(struct task_group *tg) { }
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static inline bool task_group_is_autogroup(struct task_group *tg)
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{
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return 0;
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}
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static inline struct task_group *
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autogroup_task_group(struct task_struct *p, struct task_group *tg)
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{
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return tg;
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}
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#ifdef CONFIG_SCHED_DEBUG
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static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
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{
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return 0;
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}
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#endif
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#endif /* CONFIG_SCHED_AUTOGROUP */
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