[PATCH] swsusp: freeze user space processes first

Allow swsusp to freeze processes successfully under heavy load by freezing
userspace processes before kernel threads.

[Thanks to Nigel Cunningham <nigel@suspend2.net> for suggesting the
way to go.]

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 46 insertions, 17 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 4bd68f482f2b..81d4d982f3f0 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -72,7 +72,6 @@ static int prepare_processes(void)
         int error;
 
         pm_prepare_console();
-        sys_sync();
         disable_nonboot_cpus();
 
         if (freeze_processes()) {
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 02a1b3a9fa90..8ac7c35fad77 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -12,11 +12,12 @@
 #include <linux/interrupt.h>
 #include <linux/suspend.h>
 #include <linux/module.h>
+#include <linux/syscalls.h>
 
 /* 
  * Timeout for stopping processes
  */
-#define TIMEOUT (6 * HZ)
+#define TIMEOUT (20 * HZ)
 
 
 static inline int freezeable(struct task_struct * p)
@@ -54,38 +55,62 @@ void refrigerator(void)
         current->state = save;
 }
 
+static inline void freeze_process(struct task_struct *p)
+{
+        unsigned long flags;
+
+        if (!freezing(p)) {
+                freeze(p);
+                spin_lock_irqsave(&p->sighand->siglock, flags);
+                signal_wake_up(p, 0);
+                spin_unlock_irqrestore(&p->sighand->siglock, flags);
+        }
+}
+
 /* 0 = success, else # of processes that we failed to stop */
 int freeze_processes(void)
 {
-        int todo;
+        int todo, nr_user, user_frozen;
         unsigned long start_time;
         struct task_struct *g, *p;
         unsigned long flags;
 
         printk( "Stopping tasks: " );
         start_time = jiffies;
+        user_frozen = 0;
         do {
-                todo = 0;
+                nr_user = todo = 0;
                 read_lock(&tasklist_lock);
                 do_each_thread(g, p) {
                         if (!freezeable(p))
                                 continue;
                         if (frozen(p))
                                 continue;
-
-                        freeze(p);
-                        spin_lock_irqsave(&p->sighand->siglock, flags);
-                        signal_wake_up(p, 0);
-                        spin_unlock_irqrestore(&p->sighand->siglock, flags);
-                        todo++;
+                        if (p->mm && !(p->flags & PF_BORROWED_MM)) {
+                                /* The task is a user-space one.
+                                 * Freeze it unless there's 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++;
+                        }
                 } 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)) {
-                        printk( "\n" );
-                        printk(KERN_ERR " stopping tasks timed out (%d tasks remaining)\n", todo );
+                if (todo && time_after(jiffies, start_time + TIMEOUT))
                         break;
-                }
         } while(todo);
 
         /* This does not unfreeze processes that are already frozen
@@ -94,8 +119,14 @@ int freeze_processes(void)
          * but it cleans up leftover PF_FREEZE requests.
          */
         if (todo) {
+                printk( "\n" );
+                printk(KERN_ERR " stopping tasks timed out "
+                        "after %d seconds (%d tasks remaining):\n",
+                        TIMEOUT / HZ, todo);
                 read_lock(&tasklist_lock);
-                do_each_thread(g, p)
+                do_each_thread(g, p) {
+                        if (freezeable(p) && !frozen(p))
+                                printk(KERN_ERR "  %s\n", p->comm);
                         if (freezing(p)) {
                                 pr_debug("  clean up: %s\n", p->comm);
                                 p->flags &= ~PF_FREEZE;
@@ -103,7 +134,7 @@ int freeze_processes(void)
                                 recalc_sigpending_tsk(p);
                                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
                         }
-                while_each_thread(g, p);
+                } while_each_thread(g, p);
                 read_unlock(&tasklist_lock);
                 return todo;
         }
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 8cabc405ca10..a97406b86ef3 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -138,7 +138,6 @@ static int snapshot_ioctl(struct inode *inode, struct file *filp,
         case SNAPSHOT_FREEZE:
                 if (data->frozen)
                         break;
-                sys_sync();
                 down(&pm_sem);
                 pm_prepare_console();
                 disable_nonboot_cpus();