[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, 2 insertions, 4 deletions

diff --git a/Documentation/power/kernel_threads.txt b/Documentation/power/kernel_threads.txt
index 60b548105edf..fb57784986b1 100644
--- a/Documentation/power/kernel_threads.txt
+++ b/Documentation/power/kernel_threads.txt
@@ -12,8 +12,7 @@ refrigerator. Code to do this looks like this:
         do {
                 hub_events();
                 wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list));
-                if (current->flags & PF_FREEZE)
-                        refrigerator(PF_FREEZE);
+                try_to_freeze();
         } while (!signal_pending(current));
 
 from drivers/usb/core/hub.c::hub_thread()
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index c7c3459fde43..4e1627cc5b51 100644
--- a/Documentation/power/swsusp.txt
+++ b/Documentation/power/swsusp.txt
@@ -164,8 +164,7 @@ place where the thread is safe to be frozen (no kernel semaphores
 should be held at that point and it must be safe to sleep there), and
 add:
 
-            if (current->flags & PF_FREEZE)
-                    refrigerator(PF_FREEZE);
+            try_to_freeze();
 
 If the thread is needed for writing the image to storage, you should
 instead set the PF_NOFREEZE process flag when creating the thread.