[PATCH] Unfreeze tasks after an oops in the freezer

[Oliver Neukum]

If an oops kills the task suspending or snapshotting
is system, the system is dead because the action is
never completed and the tasks never thawed.

Signed-off-by: Oliver Neukum <oneukum@xxxxxxx>
---
 include/linux/freezer.h |    2 ++
 kernel/panic.c          |    8 ++++++++
 kernel/power/process.c  |   11 +++++++++++
 3 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index 1effc8b..ab0168a 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -50,6 +50,7 @@ extern int thaw_process(struct task_struct *p);
 extern void refrigerator(void);
 extern int freeze_processes(void);
 extern void thaw_processes(void);
+extern void thaw_in_oops(void);
 
 static inline int try_to_freeze(void)
 {
@@ -181,6 +182,7 @@ static inline void freezer_count(void) {}
 static inline int freezer_should_skip(struct task_struct *p) { return 0; }
 static inline void set_freezable(void) {}
 static inline void set_freezable_with_signal(void) {}
+static inline void thaw_in_oops(void) {}
 
 #define wait_event_freezable(wq, condition)				\
 		wait_event_interruptible(wq, condition)
diff --git a/kernel/panic.c b/kernel/panic.c
index 6923167..ccdd834 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -23,6 +23,7 @@
 #include <linux/init.h>
 #include <linux/nmi.h>
 #include <linux/dmi.h>
+#include <linux/freezer.h>
 
 #define PANIC_TIMER_STEP 100
 #define PANIC_BLINK_SPD 18
@@ -355,6 +356,13 @@ void oops_exit(void)
 	do_oops_enter_exit();
 	print_oops_end_marker();
 	kmsg_dump(KMSG_DUMP_OOPS);
+	/*
+	 * if we oops while tasks are frozen, the system
+	 * will stop dead because the task that would thaw it
+	 * has been killed. So the system must be explicitly
+	 * thawed here.
+	 */
+	thaw_in_oops();
 }
 
 #ifdef WANT_WARN_ON_SLOWPATH
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 0cf3a27..c03e88b 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -22,6 +22,9 @@
  */
 #define TIMEOUT	(20 * HZ)
 
+/* in case we oops while processes are frozen */
+static bool tasks_frozen = false;
+
 static inline int freezable(struct task_struct * p)
 {
 	if ((p == current) ||
@@ -131,6 +134,7 @@ static int try_to_freeze_tasks(bool sig_only)
 			elapsed_csecs % 100);
 	}
 
+	tasks_frozen = (todo == 0);
 	return todo ? -EBUSY : 0;
 }
 
@@ -189,7 +193,14 @@ void thaw_processes(void)
 	thaw_workqueues();
 	thaw_tasks(true);
 	thaw_tasks(false);
+	tasks_frozen = false;
 	schedule();
 	printk("done.\n");
 }
 
+void thaw_in_oops(void)
+{
+	if (tasks_frozen)
+		thaw_processes();
+}
+
-- 
1.7.1

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