From 25363eb99bc43443bec354abea1e40db61280b30 Mon Sep 17 00:00:00 2001
From: Stephen Hemminger <sthemmin@microsoft.com>
Date: Wed, 5 Dec 2018 14:11:56 -0800
Subject: [PATCH 1/3] bus/vmbus: fix race in subchannel creation
[ upstream commit 4970103e89f4f828669acf3b465e984fdc891e1e ]
When using multiple queues, there was a race with the kernel
in setting up the second channel. This regression is due to a kernel change
which does not allow accessing sysfs files for Hyper-V channels that are not opened.
The fix is simple, just move the logic to detect not ready
sub channels earlier in the existing loop.
Fixes: 831dba47bd36 ("bus/vmbus: add Hyper-V virtual bus support")
Reported-by: Mohammed Gamal <mgamal@redhat.com>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
(cherry picked from commit ca17e6624251b05cf188997cffc3e1ab2e50561a)
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
drivers/bus/vmbus/linux/vmbus_uio.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/bus/vmbus/linux/vmbus_uio.c b/drivers/bus/vmbus/linux/vmbus_uio.c
index 12e97e3a4..38df4d724 100644
--- a/drivers/bus/vmbus/linux/vmbus_uio.c
+++ b/drivers/bus/vmbus/linux/vmbus_uio.c
@@ -357,6 +357,12 @@ int vmbus_uio_get_subchan(struct vmbus_channel *primary,
continue;
}
+ if (!vmbus_isnew_subchannel(primary, relid))
+ continue; /* Already know about you */
+
+ if (!vmbus_uio_ring_present(dev, relid))
+ continue; /* Ring may not be ready yet */
+
snprintf(subchan_path, sizeof(subchan_path), "%s/%lu",
chan_path, relid);
err = vmbus_uio_sysfs_read(subchan_path, "subchannel_id",
@@ -370,12 +376,6 @@ int vmbus_uio_get_subchan(struct vmbus_channel *primary,
if (subid == 0)
continue; /* skip primary channel */
- if (!vmbus_isnew_subchannel(primary, relid))
- continue;
-
- if (!vmbus_uio_ring_present(dev, relid))
- continue; /* Ring may not be ready yet */
-
err = vmbus_uio_sysfs_read(subchan_path, "monitor_id",
&monid, UINT8_MAX);
if (err) {
--
2.20.1