uml: aIO deadlock avoidance

Allow deadlocks to be avoided in the AIO code by setting the pipe to the I/O
thread non-blocking.
Signed-off-by: NJeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/um/os-Linux/aio.c

@@ -221,6 +221,11 @@ static int init_aio_24(void)
 
 	aio_req_fd_w = fds[0];
 	aio_req_fd_r = fds[1];
+
+	err = os_set_fd_block(aio_req_fd_w, 0);
+	if(err)
+		goto out_close_pipe;
+
 	err = run_helper_thread(not_aio_thread, NULL,
 				CLONE_FILES | CLONE_VM | SIGCHLD, &stack, 0);
 	if(err < 0)