[RFC][PATCH 4/4] container freezer: do not unfreeze a frozen container when the system is resumed

[Cedric Le Goater]

From: Cedric Le Goater <clg at fr.ibm.com>

When a system is resumed after a suspend, it will also unfreeze 
frozen containers. 

This patchs modifies the resume sequence to skip the tasks which 
are part of a frozen container. 

Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>
---
 include/linux/container_freezer.h |   56 ++++++++++++++++++++++++++++++++++++++
 kernel/container_freezer.c        |   20 +------------
 kernel/power/process.c            |    4 ++
 3 files changed, 62 insertions(+), 18 deletions(-)

Index: 2.6.22-rc4-mm2/include/linux/container_freezer.h
===================================================================
--- /dev/null
+++ 2.6.22-rc4-mm2/include/linux/container_freezer.h
@@ -0,0 +1,56 @@
+#ifndef _LINUX_CONTAINER_FREEZER_H
+#define _LINUX_CONTAINER_FREEZER_H
+/*
+ *  container_freezer.h -  container freezer subsystem interface
+ *
+ *  Copyright (C) Cedric Le Goater, IBM Corp. 2007
+ *
+ */
+
+#include <linux/container.h>
+
+#ifdef CONFIG_CONTAINER_FREEZER
+
+enum freezer_state {
+	STATE_RUNNING = 0,
+	STATE_FREEZING,
+	STATE_FROZEN,
+};
+
+struct freezer {
+	struct container_subsys_state css;
+	enum freezer_state state;
+	spinlock_t lock;
+};
+
+static inline struct freezer *container_freezer(
+		struct container *container)
+{
+	return container_of(
+		container_subsys_state(container, freezer_subsys_id),
+		struct freezer, css);
+}
+
+static inline int container_frozen(struct task_struct *task)
+{
+	struct container *container = task_container(task, freezer_subsys_id);
+	struct freezer *freezer = container_freezer(container);
+	enum freezer_state state;
+
+	spin_lock(&freezer->lock);
+	state = freezer->state;
+	spin_unlock(&freezer->lock);
+
+	return (state == STATE_FROZEN);
+}
+
+#else /* !CONFIG_CONTAINER_FREEZER */
+
+static inline int container_frozen(struct task_struct *task)
+{
+	return 0;
+}
+
+#endif /* !CONFIG_CONTAINER_FREEZER */
+
+#endif /* _LINUX_CONTAINER_FREEZER_H */
Index: 2.6.22-rc4-mm2/kernel/container_freezer.c
===================================================================
--- 2.6.22-rc4-mm2.orig/kernel/container_freezer.c
+++ 2.6.22-rc4-mm2/kernel/container_freezer.c
@@ -9,12 +9,8 @@
 #include <linux/fs.h>
 #include <linux/uaccess.h>
 #include <linux/freezer.h>
-
-enum freezer_state {
-	STATE_RUNNING = 0,
-	STATE_FREEZING,
-	STATE_FROZEN,
-};
+#include <linux/container.h>
+#include <linux/container_freezer.h>
 
 static const char *freezer_state_strs[] = {
 	"RUNNING\n",
@@ -22,21 +18,9 @@ static const char *freezer_state_strs[] 
 	"FROZEN\n"
 };
 
-struct freezer {
-	struct container_subsys_state css;
-	enum freezer_state state;
-	spinlock_t lock;
-};
 
 struct container_subsys freezer_subsys;
 
-static inline struct freezer *container_freezer(
-		struct container *container)
-{
-	return container_of(
-		container_subsys_state(container, freezer_subsys_id),
-		struct freezer, css);
-}
 
 static int freezer_create(struct container_subsys *ss,
 			  struct container *container)
Index: 2.6.22-rc4-mm2/kernel/power/process.c
===================================================================
--- 2.6.22-rc4-mm2.orig/kernel/power/process.c
+++ 2.6.22-rc4-mm2/kernel/power/process.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/syscalls.h>
 #include <linux/freezer.h>
+#include <linux/container_freezer.h>
 
 /* 
  * Timeout for stopping processes
@@ -169,6 +170,9 @@ static void thaw_tasks(int thaw_user_spa
 		if (!p->mm == thaw_user_space)
 			continue;
 
+		if (container_frozen(p))
+			continue;
+
 		thaw_process(p);
 	} while_each_thread(g, p);
 	read_unlock(&tasklist_lock);

--