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From:   Michael Kelley <mikelley@microsoft.com>
To:     kimbrownkd <kimbrownkd@gmail.com>, Long Li <longli@microsoft.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>
CC:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v3 3/3] Drivers: hv: vmbus: Fix race condition with new
 ring_buffer_info mutex
Thread-Topic: [PATCH v3 3/3] Drivers: hv: vmbus: Fix race condition with new
 ring_buffer_info mutex
Thread-Index: AQHU2qFBQTqhNU8HdkG1Jcl3Z4D/rqYi3CiQ
Date:   Fri, 29 Mar 2019 16:04:22 +0000
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From: Kimberly Brown <kimbrownkd@gmail.com> Sent: Thursday, March 14, 2019 =
1:05 PM
>=20
> Fix a race condition that can result in a ring buffer pointer being set
> to null while a "_show" function is reading the ring buffer's data. This
> problem was discussed here: https://lkml.org/lkml/2018/10/18/779
>=20
> To fix the race condition, add a new mutex lock to the
> "hv_ring_buffer_info" struct. Add a new function,
> "hv_ringbuffer_pre_init()", where a channel's inbound and outbound
> ring_buffer_info mutex locks are initialized.
>=20
> Acquire/release the locks in the "hv_ringbuffer_cleanup()" function,
> which is where the ring buffer pointers are set to null.
>=20
> Acquire/release the locks in the four channel-level "_show" functions
> that access ring buffer data. Remove the "const" qualifier from the
> "vmbus_channel" parameter and the "rbi" variable of the channel-level
> "_show" functions so that the locks can be acquired/released in these
> functions.
>=20
> Acquire/release the locks in hv_ringbuffer_get_debuginfo(). Remove the
> "const" qualifier from the "hv_ring_buffer_info" parameter so that the
> locks can be acquired/released in this function.
>=20
> Signed-off-by: Kimberly Brown <kimbrownkd@gmail.com>

Reviewed-by: Michael Kelley <mikelley@microsoft.com>