+ * usermodehelper_disable - prevent new helpers from being started
+ */
+int usermodehelper_disable(void)
+{
+ long retval;
+
+ usermodehelper_disabled = 1;
+ smp_mb();
+ /*
+ * From now on call_usermodehelper_exec() won't start any new
+ * helpers, so it is sufficient if running_helpers turns out to
+ * be zero at one point (it may be increased later, but that
+ * doesn't matter).
+ */
+ retval = wait_event_timeout(running_helpers_waitq,
+ atomic_read(&running_helpers) == 0,
+ RUNNING_HELPERS_TIMEOUT);
+ if (retval)
+ return 0;
+
+ usermodehelper_disabled = 0;
+ return -EAGAIN;
+}
+
+/**
+ * usermodehelper_enable - allow new helpers to be started again
+ */
+void usermodehelper_enable(void)
+{
+ usermodehelper_disabled = 0;
+}
+
+static void helper_lock(void)
+{
+ atomic_inc(&running_helpers);
+ smp_mb__after_atomic_inc();
+}
+
+static void helper_unlock(void)
+{
+ if (atomic_dec_and_test(&running_helpers))
+ wake_up(&running_helpers_waitq);
+}
+#else /* CONFIG_PM_SLEEP */
+#define usermodehelper_disabled 0
+
+static inline void helper_lock(void) {}
+static inline void helper_unlock(void) {}
+#endif /* CONFIG_PM_SLEEP */
+
+/**
+ * call_usermodehelper_setup - prepare to call a usermode helper
+ * @path: path to usermode executable
+ * @argv: arg vector for process
+ * @envp: environment for process
+ * @gfp_mask: gfp mask for memory allocation
+ *
+ * Returns either %NULL on allocation failure, or a subprocess_info
+ * structure. This should be passed to call_usermodehelper_exec to
+ * exec the process and free the structure.
+ */
+struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
+ char **envp, gfp_t gfp_mask)
+{
+ struct subprocess_info *sub_info;
+ sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
+ if (!sub_info)
+ goto out;
+
+ INIT_WORK(&sub_info->work, __call_usermodehelper);
+ sub_info->path = path;
+ sub_info->argv = argv;
+ sub_info->envp = envp;
+ out:
+ return sub_info;
+}
+EXPORT_SYMBOL(call_usermodehelper_setup);
+
+/**
+ * call_usermodehelper_setfns - set a cleanup/init function
+ * @info: a subprocess_info returned by call_usermodehelper_setup
+ * @cleanup: a cleanup function
+ * @init: an init function
+ * @data: arbitrary context sensitive data
+ *
+ * The init function is used to customize the helper process prior to
+ * exec. A non-zero return code causes the process to error out, exit,
+ * and return the failure to the calling process
+ *
+ * The cleanup function is just before ethe subprocess_info is about to
+ * be freed. This can be used for freeing the argv and envp. The
+ * Function must be runnable in either a process context or the
+ * context in which call_usermodehelper_exec is called.
+ */
+void call_usermodehelper_setfns(struct subprocess_info *info,
+ int (*init)(struct subprocess_info *info),
+ void (*cleanup)(struct subprocess_info *info),
+ void *data)
+{
+ info->cleanup = cleanup;
+ info->init = init;
+ info->data = data;
+}
+EXPORT_SYMBOL(call_usermodehelper_setfns);
+
+/**
+ * call_usermodehelper_exec - start a usermode application
+ * @sub_info: information about the subprocessa