uml: simplify helper stack handling

run_helper and run_helper_thread had arguments which were the same in all
callers.  run_helper's stack_out was always NULL and run_helper_thread's
stack_order was always 0.  These are now gone, and the constants folded
into the code.

Also fixed leaks of the helper stack in the AIO and SIGIO code.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index 4d9fb263..930b261 100644
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -239,11 +239,9 @@
 /* execvp.c */
 extern int execvp_noalloc(char *buf, const char *file, char *const argv[]);
 /* helper.c */
-extern int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
-		      unsigned long *stack_out);
+extern int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv);
 extern int run_helper_thread(int (*proc)(void *), void *arg,
-			     unsigned int flags, unsigned long *stack_out,
-			     int stack_order);
+			     unsigned int flags, unsigned long *stack_out);
 extern int helper_wait(int pid);