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>

1 files changed, 6 insertions, 0 deletions

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){