From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
devel@linuxdriverproject.org,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>
Subject: Re: [PATCH net-next 3/4] hv_netvsc: reset net_device_ctx->nvdev with rcu_assign_pointer()
Date: Tue, 31 Oct 2017 15:40:06 +0100 [thread overview]
Message-ID: <8760avxtx5.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <1509458998.3828.19.camel@edumazet-glaptop3.roam.corp.google.com> (Eric Dumazet's message of "Tue, 31 Oct 2017 07:09:58 -0700")
Eric Dumazet <eric.dumazet@gmail.com> writes:
> On Tue, 2017-10-31 at 14:42 +0100, Vitaly Kuznetsov wrote:
>> RCU_INIT_POINTER() is not suitable here as it doesn't give us ordering
>> guarantees (see the comment in rcupdate.h). This is also not a hotpath.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> drivers/net/hyperv/netvsc.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
>> index bfc79698b8f4..12efb3e34775 100644
>> --- a/drivers/net/hyperv/netvsc.c
>> +++ b/drivers/net/hyperv/netvsc.c
>> @@ -560,7 +560,7 @@ void netvsc_device_remove(struct hv_device *device)
>>
>> netvsc_revoke_buf(device, net_device);
>>
>> - RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);
>> + rcu_assign_pointer(net_device_ctx->nvdev, NULL);
>
> I see no point for this patch.
>
> Setting a NULL pointer needs no barrier at all.
Oh, sorry, I got confused by the comment near RCU_INIT_POINTER() in
rcupdate.h. Now looking at their definitions I see.
This patch can of course be dropped from the series.
--
Vitaly
next prev parent reply other threads:[~2017-10-31 14:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 13:42 [PATCH net-next 0/4] hv_netvsc: fix some crashes and hangs on channel/mtu changes Vitaly Kuznetsov
2017-10-31 13:42 ` [PATCH net-next 1/4] hv_netvsc: netvsc_teardown_gpadl() split Vitaly Kuznetsov
2017-10-31 16:37 ` Stephen Hemminger
2017-10-31 13:42 ` [PATCH net-next 2/4] hv_netvsc: protect nvdev->extension with RCU Vitaly Kuznetsov
2017-10-31 16:44 ` Stephen Hemminger
2017-10-31 17:13 ` Vitaly Kuznetsov
2017-11-02 10:27 ` Vitaly Kuznetsov
2017-10-31 13:42 ` [PATCH net-next 3/4] hv_netvsc: reset net_device_ctx->nvdev with rcu_assign_pointer() Vitaly Kuznetsov
2017-10-31 14:09 ` Eric Dumazet
2017-10-31 14:40 ` Vitaly Kuznetsov [this message]
2017-10-31 14:44 ` David Miller
2017-10-31 14:50 ` Vitaly Kuznetsov
2017-10-31 16:45 ` Stephen Hemminger
2017-10-31 13:42 ` [PATCH net-next 4/4] hv_netvsc: hide warnings about uninitialized/missing rndis device Vitaly Kuznetsov
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