uml: DEBUG_SHIRQ fixes

DEBUG_SHIRQ generates spurious interrupts, triggering handlers such as
mconsole_interrupt() or line_interrupt().  They expect data to be available to
be read from their sockets/pipes, but in the case of spurious interrupts, the
host didn't actually send anything, so UML hangs in read() and friends.
Setting those fd's as O_NONBLOCK makes DEBUG_SHIRQ-enabled UML kernels boot
and run correctly.

Signed-off-by: Eduard-Gabriel Munteanu <maxdamage@aladin.ro>
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>

4 files changed, 23 insertions, 3 deletions

diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index 13f0bf852b2a..5d1289d33410 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -170,7 +170,13 @@ static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out)
                 err = -EINVAL;
                 goto out_close;
         }
-        return err ;
+
+        if (os_set_fd_block(*fd_out, 0)) {
+                printk("winch_tramp: failed to set thread_fd non-blocking.\n");
+                goto out_close;
+        }
+
+        return err;
 
  out_close:
         os_close_file(fds[1]);
diff --git a/arch/um/drivers/mconsole_user.c b/arch/um/drivers/mconsole_user.c
index 62e5ad63181a..f31e71546e52 100644
--- a/arch/um/drivers/mconsole_user.c
+++ b/arch/um/drivers/mconsole_user.c
@@ -86,8 +86,9 @@ int mconsole_get_request(int fd, struct mc_request *req)
         int len;
 
         req->originlen = sizeof(req->origin);
-        req->len = recvfrom(fd, &req->request, sizeof(req->request), 0,
-                            (struct sockaddr *) req->origin, &req->originlen);
+        req->len = recvfrom(fd, &req->request, sizeof(req->request),
+                            MSG_DONTWAIT, (struct sockaddr *) req->origin,
+                            &req->originlen);
         if (req->len < 0)
                 return 0;
 
diff --git a/arch/um/drivers/ubd_user.c b/arch/um/drivers/ubd_user.c
index 4707b3f14c2f..41d254bd38df 100644
--- a/arch/um/drivers/ubd_user.c
+++ b/arch/um/drivers/ubd_user.c
@@ -43,6 +43,12 @@ int start_io_thread(unsigned long sp, int *fd_out)
         kernel_fd = fds[0];
         *fd_out = fds[1];
 
+        err = os_set_fd_block(*fd_out, 0);
+        if (err) {
+                printk("start_io_thread - failed to set nonblocking I/O.\n");
+                goto out_close;
+        }
+
         pid = clone(io_thread, (void *) sp, CLONE_FILES | CLONE_VM | SIGCHLD,
                     NULL);
         if(pid < 0){
diff --git a/arch/um/drivers/xterm.c b/arch/um/drivers/xterm.c
index 571c2b3325d5..fe238e03a300 100644
--- a/arch/um/drivers/xterm.c
+++ b/arch/um/drivers/xterm.c
@@ -151,6 +151,13 @@ int xterm_open(int input, int output, int primary, void *d,
                 goto out;
         }
 
+        err = os_set_fd_block(new, 0);
+        if (err) {
+                printk("xterm_open : failed to set xterm descriptor "
+                       "non-blocking, err = %d\n", -err);
+                goto out;
+        }
+
         CATCH_EINTR(err = tcgetattr(new, &data->tt));
         if(err){
                 new = err;