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authorMike Galbraith <efault@gmx.de>2012-10-28 12:19:23 -0700
committerIngo Molnar <mingo@kernel.org>2012-10-30 10:26:04 +0100
commit5258f386ea4e8454bc801fb443e8a4217da1947c (patch)
treec97487f040b95f83a2c9d31d51cbfe57f35e59e3 /kernel/sched
parent8ed92e51f99c2199c64cb33b4ba95ab12940a94c (diff)
downloadlinaro-lsk-5258f386ea4e8454bc801fb443e8a4217da1947c.tar.gz
sched/autogroup: Fix crash on reboot when autogroup is disabled
Due to these two commits: 8323f26ce342 sched: Fix race in task_group() 800d4d30c8f2 sched, autogroup: Stop going ahead if autogroup is disabled ... autogroup scheduling's dynamic knobs are wrecked. With both patches applied, all you have to do to crash a box is disable autogroup during boot up, then reboot.. boom, NULL pointer dereference due to 800d4d30 not allowing autogroup to move things, and 8323f26ce making that the only way to switch runqueues. Remove most of the (dysfunctional) knobs and turn the remaining sched_autogroup_enabled knob readonly. If the user fiddles with cgroups hereafter, once tasks are moved, autogroup won't mess with them again unless they call setsid(). No knobs, no glitz, nada, just a cute little thing folks can turn on if they don't want to muck about with cgroups and/or systemd. Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Xiaotian Feng <xtfeng@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Xiaotian Feng <dannyfeng@tencent.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> # v3.6 Link: http://lkml.kernel.org/r/1351451963.4999.8.camel@maggy.simpson.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/auto_group.c68
-rw-r--r--kernel/sched/auto_group.h9
2 files changed, 12 insertions, 65 deletions
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c
index 0984a21076a..0f1bacb005a 100644
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -110,6 +110,9 @@ out_fail:
bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
{
+ if (!sysctl_sched_autogroup_enabled)
+ return false;
+
if (tg != &root_task_group)
return false;
@@ -143,15 +146,11 @@ 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);
}
@@ -159,8 +158,11 @@ out:
/* Allocates GFP_KERNEL, cannot be called under any spinlock */
void sched_autogroup_create_attach(struct task_struct *p)
{
- struct autogroup *ag = autogroup_create();
+ struct autogroup *ag;
+ if (!sysctl_sched_autogroup_enabled)
+ return;
+ ag = autogroup_create();
autogroup_move_group(p, ag);
/* drop extra reference added by autogroup_create() */
autogroup_kref_put(ag);
@@ -176,11 +178,15 @@ EXPORT_SYMBOL(sched_autogroup_detach);
void sched_autogroup_fork(struct signal_struct *sig)
{
+ if (!sysctl_sched_autogroup_enabled)
+ return;
sig->autogroup = autogroup_task_get(current);
}
void sched_autogroup_exit(struct signal_struct *sig)
{
+ if (!sysctl_sched_autogroup_enabled)
+ return;
autogroup_kref_put(sig->autogroup);
}
@@ -193,58 +199,6 @@ static int __init setup_autogroup(char *str)
__setup("noautogroup", setup_autogroup);
-#ifdef CONFIG_PROC_FS
-
-int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
-{
- static unsigned long next = INITIAL_JIFFIES;
- struct autogroup *ag;
- int err;
-
- if (nice < -20 || nice > 19)
- return -EINVAL;
-
- err = security_task_setnice(current, nice);
- if (err)
- return err;
-
- if (nice < 0 && !can_nice(current, nice))
- return -EPERM;
-
- /* this is a heavy operation taking global locks.. */
- if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
- return -EAGAIN;
-
- next = HZ / 10 + jiffies;
- ag = autogroup_task_get(p);
-
- down_write(&ag->lock);
- err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
- if (!err)
- ag->nice = nice;
- up_write(&ag->lock);
-
- autogroup_kref_put(ag);
-
- return err;
-}
-
-void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
-{
- struct autogroup *ag = autogroup_task_get(p);
-
- if (!task_group_is_autogroup(ag->tg))
- goto out;
-
- down_read(&ag->lock);
- seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
- up_read(&ag->lock);
-
-out:
- autogroup_kref_put(ag);
-}
-#endif /* CONFIG_PROC_FS */
-
#ifdef CONFIG_SCHED_DEBUG
int autogroup_path(struct task_group *tg, char *buf, int buflen)
{
diff --git a/kernel/sched/auto_group.h b/kernel/sched/auto_group.h
index 8bd04714281..4552c6bf79d 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;
@@ -29,9 +24,7 @@ extern bool task_wants_autogroup(struct task_struct *p, struct task_group *tg);
static inline struct task_group *
autogroup_task_group(struct task_struct *p, struct task_group *tg)
{
- int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
-
- if (enabled && task_wants_autogroup(p, tg))
+ if (task_wants_autogroup(p, tg))
return p->signal->autogroup->tg;
return tg;