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