Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled"

This reverts commit 5258f386ea4e8454bc801fb443e8a4217da1947c,
because the underlying autogroups bug got fixed upstream in
a better way, via:

  fd8ef11730f1 Revert "sched, autogroup: Stop going ahead if autogroup is disabled"

Cc: Mike Galbraith <efault@gmx.de>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 57 insertions, 11 deletions

diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c
index 0f1bacb005a4..0984a21076a3 100644
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -110,9 +110,6 @@ 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;
 
@@ -146,11 +143,15 @@ 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);
 }
@@ -158,11 +159,8 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 void sched_autogroup_create_attach(struct task_struct *p)
 {
-        struct autogroup *ag;
+        struct autogroup *ag = autogroup_create();
 
-        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);
@@ -178,15 +176,11 @@ 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);
 }
 
@@ -199,6 +193,58 @@ 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)
 {