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authorMike Galbraith2012-12-03 06:25:25 +0100
committerLinus Torvalds2012-12-03 11:10:24 -0800
commitfd8ef11730f1d03d5d6555aa53126e9e34f52f12 (patch)
treeb5121d6016bf20b46ae0fdc760b9e2f4e836bf21 /kernel/sched
parentd3594ea2b343fbbabaaebeb4ce4e1f29e88ab6b3 (diff)
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>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/auto_group.c4
-rw-r--r--kernel/sched/auto_group.h5
2 files changed, 0 insertions, 9 deletions
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c
index 0984a21076a3..15f60d01198b 100644
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -143,15 +143,11 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
p->signal->autogroup = autogroup_kref_get(ag);
- if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
- goto out;
-
t = p;
do {
sched_move_task(t);
} while_each_thread(p, t);
-out:
unlock_task_sighand(p, &flags);
autogroup_kref_put(prev);
}
diff --git a/kernel/sched/auto_group.h b/kernel/sched/auto_group.h
index 8bd047142816..443232ebbb53 100644
--- a/kernel/sched/auto_group.h
+++ b/kernel/sched/auto_group.h
@@ -4,11 +4,6 @@
#include <linux/rwsem.h>
struct autogroup {
- /*
- * reference doesn't mean how many thread attach to this
- * autogroup now. It just stands for the number of task
- * could use this autogroup.
- */
struct kref kref;
struct task_group *tg;
struct rw_semaphore lock;