3 files changed, 58 insertions, 13 deletions

diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index b087377ae2c4..dd99c329e161 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -110,10 +110,27 @@ call_usermodehelper(char *path, char **argv, char **envp, int wait)
 
 extern struct ctl_table usermodehelper_table[];
 
+enum umh_disable_depth {
+        UMH_ENABLED = 0,
+        UMH_FREEZING,
+        UMH_DISABLED,
+};
+
 extern void usermodehelper_init(void);
 
-extern int usermodehelper_disable(void);
-extern void usermodehelper_enable(void);
+extern int __usermodehelper_disable(enum umh_disable_depth depth);
+extern void __usermodehelper_set_disable_depth(enum umh_disable_depth depth);
+
+static inline int usermodehelper_disable(void)
+{
+        return __usermodehelper_disable(UMH_DISABLED);
+}
+
+static inline void usermodehelper_enable(void)
+{
+        __usermodehelper_set_disable_depth(UMH_ENABLED);
+}
+
 extern int usermodehelper_read_trylock(void);
 extern long usermodehelper_read_lock_wait(long timeout);
 extern void usermodehelper_read_unlock(void);
diff --git a/kernel/kmod.c b/kernel/kmod.c
index da7fcca279f9..05698a7415fe 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -322,7 +322,7 @@ static void __call_usermodehelper(struct work_struct *work)
  * land has been frozen during a system-wide hibernation or suspend operation).
  * Should always be manipulated under umhelper_sem acquired for write.
  */
-static int usermodehelper_disabled = 1;
+static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
 
 /* Number of helpers running */
 static atomic_t running_helpers = ATOMIC_INIT(0);
@@ -347,13 +347,30 @@ static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
 
 int usermodehelper_read_trylock(void)
 {
+        DEFINE_WAIT(wait);
         int ret = 0;
 
         down_read(&umhelper_sem);
-        if (usermodehelper_disabled) {
+        for (;;) {
+                prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
+                                TASK_INTERRUPTIBLE);
+                if (!usermodehelper_disabled)
+                        break;
+
+                if (usermodehelper_disabled == UMH_DISABLED)
+                        ret = -EAGAIN;
+
                 up_read(&umhelper_sem);
-                ret = -EAGAIN;
+
+                if (ret)
+                        break;
+
+                schedule();
+                try_to_freeze();
+
+                down_read(&umhelper_sem);
         }
+        finish_wait(&usermodehelper_disabled_waitq, &wait);
         return ret;
 }
 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
@@ -392,25 +409,35 @@ void usermodehelper_read_unlock(void)
 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 
 /**
- * usermodehelper_enable - allow new helpers to be started again
+ * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
+ * depth: New value to assign to usermodehelper_disabled.
+ *
+ * Change the value of usermodehelper_disabled (under umhelper_sem locked for
+ * writing) and wakeup tasks waiting for it to change.
  */
-void usermodehelper_enable(void)
+void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
 {
         down_write(&umhelper_sem);
-        usermodehelper_disabled = 0;
+        usermodehelper_disabled = depth;
         wake_up(&usermodehelper_disabled_waitq);
         up_write(&umhelper_sem);
 }
 
 /**
- * usermodehelper_disable - prevent new helpers from being started
+ * __usermodehelper_disable - Prevent new helpers from being started.
+ * @depth: New value to assign to usermodehelper_disabled.
+ *
+ * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
  */
-int usermodehelper_disable(void)
+int __usermodehelper_disable(enum umh_disable_depth depth)
 {
         long retval;
 
+        if (!depth)
+                return -EINVAL;
+
         down_write(&umhelper_sem);
-        usermodehelper_disabled = 1;
+        usermodehelper_disabled = depth;
         up_write(&umhelper_sem);
 
         /*
@@ -425,7 +452,7 @@ int usermodehelper_disable(void)
         if (retval)
                 return 0;
 
-        usermodehelper_enable();
+        __usermodehelper_set_disable_depth(UMH_ENABLED);
         return -EAGAIN;
 }
 
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 56eaac7e88ab..19db29f67558 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -123,7 +123,7 @@ int freeze_processes(void)
 {
         int error;
 
-        error = usermodehelper_disable();
+        error = __usermodehelper_disable(UMH_FREEZING);
         if (error)
                 return error;
 
@@ -135,6 +135,7 @@ int freeze_processes(void)
         error = try_to_freeze_tasks(true);
         if (!error) {
                 printk("done.");
+                __usermodehelper_set_disable_depth(UMH_DISABLED);
                 oom_killer_disable();
         }
         printk("\n");