vfio: Fix runaway interruptible timeout (db7d4d7f) · Commits · 戴 / test

Commit ("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: Cc: stable@vger.kernel.org # v4.0

drivers/vfio/vfio.c

+18 −3

Original line number	Diff line number	Diff line
		@@ -710,6 +710,8 @@ void vfio_del_group_dev(struct device dev)
		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
		@@ -755,9 +757,22 @@ void vfio_del_group_dev(struct device dev)

		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);

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