[PATCH] Cleanup patch for process freezing

1. Establish a simple API for process freezing defined in linux/include/sched.h:

   frozen(process)		Check for frozen process
   freezing(process)		Check if a process is being frozen
   freeze(process)		Tell a process to freeze (go to refrigerator)
   thaw_process(process)	Restart process
   frozen_process(process)	Process is frozen now

2. Remove all references to PF_FREEZE and PF_FROZEN from all
   kernel sources except sched.h

3. Fix numerous locations where try_to_freeze is manually done by a driver

4. Remove the argument that is no longer necessary from two function calls.

5. Some whitespace cleanup

6. Clear potential race in refrigerator (provides an open window of PF_FREEZE
   cleared before setting PF_FROZEN, recalc_sigpending does not check
   PF_FROZEN).

This patch does not address the problem of freeze_processes() violating the rule
that a task may only modify its own flags by setting PF_FREEZE. This is not clean
in an SMP environment. freeze(process) is therefore not SMP safe!

Signed-off-by: Christoph Lameter <christoph@lameter.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 3 insertions, 3 deletions

diff --git a/mm/pdflush.c b/mm/pdflush.c
index 38ce279cc8cd..d6781951267e 100644
--- a/mm/pdflush.c
+++ b/mm/pdflush.c
@@ -105,7 +105,7 @@ static int __pdflush(struct pdflush_work *my_work)
                 spin_unlock_irq(&pdflush_lock);
 
                 schedule();
-                if (try_to_freeze(PF_FREEZE)) {
+                if (try_to_freeze()) {
                         spin_lock_irq(&pdflush_lock);
                         continue;
                 }
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4b8e62a19370..1fa312a8db77 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1216,8 +1216,8 @@ static int kswapd(void *p)
         order = 0;
         for ( ; ; ) {
                 unsigned long new_order;
-                if (current->flags & PF_FREEZE)
-                        refrigerator(PF_FREEZE);
+
+                try_to_freeze();
 
                 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
                 new_order = pgdat->kswapd_max_order;