[PATCH] swsusp: Untangle freeze_processes

Move the loop from freeze_processes() to a separate function and call it
independently for user space processes and kernel threads so that the order
of freezing tasks is clearly visible.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@suspend2.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 54 insertions, 30 deletions

diff --git a/kernel/power/process.c b/kernel/power/process.c
index fd0ebb942f50..99eeb119b06d 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -86,24 +86,23 @@ static inline int is_user_space(struct task_struct *p)
         return p->mm && !(p->flags & PF_BORROWED_MM);
 }
 
-/* 0 = success, else # of processes that we failed to stop */
-int freeze_processes(void)
+static unsigned int try_to_freeze_tasks(int freeze_user_space)
 {
-        int todo, nr_user, user_frozen;
-        unsigned long start_time;
         struct task_struct *g, *p;
+        unsigned long end_time;
+        unsigned int todo;
 
-        printk("Stopping tasks... ");
-        start_time = jiffies;
-        user_frozen = 0;
+        end_time = jiffies + TIMEOUT;
         do {
-                nr_user = todo = 0;
+                todo = 0;
                 read_lock(&tasklist_lock);
                 do_each_thread(g, p) {
                         if (!freezeable(p))
                                 continue;
+
                         if (frozen(p))
                                 continue;
+
                         if (p->state == TASK_TRACED &&
                             (frozen(p->parent) ||
                              p->parent->state == TASK_STOPPED)) {
@@ -111,51 +110,76 @@ int freeze_processes(void)
                                 continue;
                         }
                         if (is_user_space(p)) {
+                                if (!freeze_user_space)
+                                        continue;
+
                                 /* Freeze the task unless there is a vfork
                                  * completion pending
                                  */
                                 if (!p->vfork_done)
                                         freeze_process(p);
-                                nr_user++;
                         } else {
-                                /* Freeze only if the user space is frozen */
-                                if (user_frozen)
-                                        freeze_process(p);
-                                todo++;
+                                if (freeze_user_space)
+                                        continue;
+
+                                freeze_process(p);
                         }
+                        todo++;
                 } while_each_thread(g, p);
                 read_unlock(&tasklist_lock);
-                todo += nr_user;
-                if (!user_frozen && !nr_user) {
-                        sys_sync();
-                        start_time = jiffies;
-                }
-                user_frozen = !nr_user;
                 yield();                        /* Yield is okay here */
-                if (todo && time_after(jiffies, start_time + TIMEOUT))
+                if (todo && time_after(jiffies, end_time))
                         break;
-        } while(todo);
+        } while (todo);
 
-        /* This does not unfreeze processes that are already frozen
-         * (we have slightly ugly calling convention in that respect,
-         * and caller must call thaw_processes() if something fails),
-         * but it cleans up leftover PF_FREEZE requests.
-         */
         if (todo) {
+                /* This does not unfreeze processes that are already frozen
+                 * (we have slightly ugly calling convention in that respect,
+                 * and caller must call thaw_processes() if something fails),
+                 * but it cleans up leftover PF_FREEZE requests.
+                 */
                 printk("\n");
-                printk(KERN_ERR "Stopping tasks timed out "
-                        "after %d seconds (%d tasks remaining):\n",
-                        TIMEOUT / HZ, todo);
+                printk(KERN_ERR "Stopping %s timed out after %d seconds "
+                                "(%d tasks refusing to freeze):\n",
+                                freeze_user_space ? "user space processes" :
+                                        "kernel threads",
+                                TIMEOUT / HZ, todo);
                 read_lock(&tasklist_lock);
                 do_each_thread(g, p) {
+                        if (is_user_space(p) == !freeze_user_space)
+                                continue;
+
                         if (freezeable(p) && !frozen(p))
                                 printk(KERN_ERR " %s\n", p->comm);
+
                         cancel_freezing(p);
                 } while_each_thread(g, p);
                 read_unlock(&tasklist_lock);
-                return todo;
         }
 
+        return todo;
+}
+
+/**
+ *      freeze_processes - tell processes to enter the refrigerator
+ *
+ *      Returns 0 on success, or the number of processes that didn't freeze,
+ *      although they were told to.
+ */
+int freeze_processes(void)
+{
+        unsigned int nr_unfrozen;
+
+        printk("Stopping tasks ... ");
+        nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
+        if (nr_unfrozen)
+                return nr_unfrozen;
+
+        sys_sync();
+        nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
+        if (nr_unfrozen)
+                return nr_unfrozen;
+
         printk("done.\n");
         BUG_ON(in_atomic());
         return 0;