Freezer: avoid freezing kernel threads prematurely

[pandora-kernel.git] / kernel / power / process.c

diff --git a/kernel/power/process.c b/kernel/power/process.c
index b850173..e1bcded 100644 (file)
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -40,7 +40,7 @@ static inline void frozen_process(void)
                current->flags |= PF_FROZEN;
                wmb();
        }
-       clear_tsk_thread_flag(current, TIF_FREEZE);
+       clear_freeze_flag(current);
 }
 
 /* Refrigerator is place where frozen processes are stored :-). */
@@ -75,17 +75,16 @@ void refrigerator(void)
        current->state = save;
 }
 
-static inline void freeze_process(struct task_struct *p)
+static void freeze_task(struct task_struct *p)
 {
        unsigned long flags;
 
        if (!freezing(p)) {
                rmb();
                if (!frozen(p)) {
+                       set_freeze_flag(p);
                        if (p->state == TASK_STOPPED)
                                force_sig_specific(SIGSTOP, p);
-
-                       freeze(p);
                        spin_lock_irqsave(&p->sighand->siglock, flags);
                        signal_wake_up(p, p->state == TASK_STOPPED);
                        spin_unlock_irqrestore(&p->sighand->siglock, flags);
@@ -99,18 +98,13 @@ static void cancel_freezing(struct task_struct *p)
 
        if (freezing(p)) {
                pr_debug("  clean up: %s\n", p->comm);
-               do_not_freeze(p);
+               clear_freeze_flag(p);
                spin_lock_irqsave(&p->sighand->siglock, flags);
                recalc_sigpending_and_wake(p);
                spin_unlock_irqrestore(&p->sighand->siglock, flags);
        }
 }
 
-static inline int is_user_space(struct task_struct *p)
-{
-       return p->mm && !(p->flags & PF_BORROWED_MM);
-}
-
 static unsigned int try_to_freeze_tasks(int freeze_user_space)
 {
        struct task_struct *g, *p;
@@ -122,20 +116,34 @@ static unsigned int try_to_freeze_tasks(int freeze_user_space)
                todo = 0;
                read_lock(&tasklist_lock);
                do_each_thread(g, p) {
-                       if (!freezeable(p))
-                               continue;
-
-                       if (frozen(p))
+                       if (frozen(p) || !freezeable(p))
                                continue;
 
-                       if (p->state == TASK_TRACED && frozen(p->parent)) {
-                               cancel_freezing(p);
-                               continue;
+                       if (freeze_user_space) {
+                               if (p->state == TASK_TRACED &&
+                                   frozen(p->parent)) {
+                                       cancel_freezing(p);
+                                       continue;
+                               }
+                               /*
+                                * Kernel threads should not have TIF_FREEZE set
+                                * at this point, so we must ensure that either
+                                * p->mm is not NULL *and* PF_BORROWED_MM is
+                                * unset, or TIF_FRREZE is left unset.
+                                * The task_lock() is necessary to prevent races
+                                * with exit_mm() or use_mm()/unuse_mm() from
+                                * occuring.
+                                */
+                               task_lock(p);
+                               if (!p->mm || (p->flags & PF_BORROWED_MM)) {
+                                       task_unlock(p);
+                                       continue;
+                               }
+                               freeze_task(p);
+                               task_unlock(p);
+                       } else {
+                               freeze_task(p);
                        }
-                       if (freeze_user_space && !is_user_space(p))
-                               continue;
-
-                       freeze_process(p);
                        if (!freezer_should_skip(p))
                                todo++;
                } while_each_thread(g, p);
@@ -152,22 +160,16 @@ static unsigned int try_to_freeze_tasks(int freeze_user_space)
                 * but it cleans up leftover PF_FREEZE requests.
                 */
                printk("\n");
-               printk(KERN_ERR "Stopping %s timed out after %d seconds "
+               printk(KERN_ERR "Freezing of %s timed out after %d seconds "
                                "(%d tasks refusing to freeze):\n",
-                               freeze_user_space ? "user space processes" :
-                                       "kernel threads",
+                               freeze_user_space ? "user space " : "tasks ",
                                TIMEOUT / HZ, todo);
                show_state();
                read_lock(&tasklist_lock);
                do_each_thread(g, p) {
-                       if (freeze_user_space && !is_user_space(p))
-                               continue;
-
                        task_lock(p);
-                       if (freezeable(p) && !frozen(p) &&
-                           !freezer_should_skip(p))
+                       if (freezing(p) && !freezer_should_skip(p))
                                printk(KERN_ERR " %s\n", p->comm);
-
                        cancel_freezing(p);
                        task_unlock(p);
                } while_each_thread(g, p);
@@ -211,7 +213,7 @@ static void thaw_tasks(int thaw_user_space)
                if (!freezeable(p))
                        continue;
 
-               if (is_user_space(p) == !thaw_user_space)
+               if (!p->mm == thaw_user_space)
                        continue;
 
                thaw_process(p);