uml: fix spurious IRQ testing

The spurious IRQ testing in request_irq is mishandled in um_request_irq, which
sets the incoming file descriptors non-blocking only after request_irq
succeeds.  This results in the spurious irq calling read on a blocking
descriptor, and a hang.

Fixed by reversing the O_NONBLOCK setting and the request_irq call.

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, 7 insertions, 6 deletions

diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 70c2d625b070..ba11ccd6a8a3 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -347,14 +347,15 @@ int um_request_irq(unsigned int irq, int fd, int type,
 {
         int err;
 
-        err = request_irq(irq, handler, irqflags, devname, dev_id);
-        if (err)
-                return err;
-
-        if (fd != -1)
+        if (fd != -1) {
                 err = activate_fd(irq, fd, type, dev_id);
-        return err;
+                if (err)
+                        return err;
+        }
+
+        return request_irq(irq, handler, irqflags, devname, dev_id);
 }
+
 EXPORT_SYMBOL(um_request_irq);
 EXPORT_SYMBOL(reactivate_fd);