Patch "vfio: Fix runaway interruptible timeout" has been added to the 4.0-stable tree

Patch "vfio: Fix runaway interruptible timeout" has been added to the 4.0-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    vfio: Fix runaway interruptible timeout

to the 4.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vfio-fix-runaway-interruptible-timeout.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From db7d4d7f40215843000cb9d441c9149fd42ea36b Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@redhat.com>
Date: Fri, 1 May 2015 16:31:41 -0600
Subject: vfio: Fix runaway interruptible timeout

From: Alex Williamson <alex.williamson@redhat.com>

commit db7d4d7f40215843000cb9d441c9149fd42ea36b upstream.

Commit 13060b64b819 ("vfio: Add and use device request op for vfio
bus drivers") incorrectly makes use of an interruptible timeout.
When interrupted, the signal remains pending resulting in subsequent
timeouts occurring instantly.  This makes the loop spin at a much
higher rate than intended.

Instead of making this completely non-interruptible, we can change
this into a sort of interruptible-once behavior and use the "once"
to log debug information.  The driver API doesn't allow us to abort
and return an error code.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Fixes: 13060b64b819
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/vfio/vfio.c |   21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -711,6 +711,8 @@ void *vfio_del_group_dev(struct device *
 	void *device_data = device->device_data;
 	struct vfio_unbound_dev *unbound;
 	unsigned int i = 0;
+	long ret;
+	bool interrupted = false;
 
 	/*
 	 * The group exists so long as we have a device reference.  Get
@@ -756,9 +758,22 @@ void *vfio_del_group_dev(struct device *
 
 		vfio_device_put(device);
 
-	} while (wait_event_interruptible_timeout(vfio.release_q,
-						  !vfio_dev_present(group, dev),
-						  HZ * 10) <= 0);
+		if (interrupted) {
+			ret = wait_event_timeout(vfio.release_q,
+					!vfio_dev_present(group, dev), HZ * 10);
+		} else {
+			ret = wait_event_interruptible_timeout(vfio.release_q,
+					!vfio_dev_present(group, dev), HZ * 10);
+			if (ret == -ERESTARTSYS) {
+				interrupted = true;
+				dev_warn(dev,
+					 "Device is currently in use, task"
+					 " \"%s\" (%d) "
+					 "blocked until device is released",
+					 current->comm, task_pid_nr(current));
+			}
+		}
+	} while (ret <= 0);
 
 	vfio_group_put(group);
 


Patches currently in stable-queue which might be from alex.williamson@redhat.com are

queue-4.0/vfio-fix-runaway-interruptible-timeout.patch