From: Arend Van Spriel <arend.vanspriel@broadcom.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Felix Fietkau" <nbd@nbd.name>,
linux-wireless@vger.kernel.org, johannes@sipsolutions.net
Subject: Re: [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues
Date: Tue, 16 Apr 2019 10:04:24 +0200 [thread overview]
Message-ID: <73b18131-2777-da5c-a6ee-9d9b3e13cd06@broadcom.com> (raw)
In-Reply-To: <20190416074444.pdubbh6fbibdnhi7@gondor.apana.org.au>
On 4/16/2019 9:44 AM, Herbert Xu wrote:
> On Sun, Apr 14, 2019 at 11:44:17AM +0200, Arend Van Spriel wrote:
>> + Herbert
>>
>> On 3/16/2019 7:14 PM, Toke Høiland-Jørgensen wrote:
>>> Felix Fietkau <nbd@nbd.name> writes:
>>>
>>>> When using iTXQ, tx sequence number allocation and statistics are run at
>>>> dequeue time. Because of that, it is safe to enable NETIF_F_LLTX, which
>>>> allows tx handlers to run on multiple CPUs in parallel.
>>>
>>> Cool, didn't know about that flag.
>>
>> It is water under the bridge as this patch got applied already, but I
>> stumbled upon it just recently and didn't know about that flag either. So I
>> looked for more information about it and found the definition [1], but the
>> comment seemed important enough to send this reply.
>>
>> NETIF_F_LLTX_BIT, /* LockLess TX - deprecated. Please */
>> /* do not use LLTX in new drivers */
>
> The most obvious problem with LLTX is that it can cause AF_PACKET
> to see packets twice. But the more subtle issue is that with a
> proper design this lock should have no contention anyway.
>
> So please explain why you want to use this in your driver and where
> the contention is coming from?
Hi Herbert,
I was just writing up an email clarifying my question. But let me
summarize this email thread. The patch from Felix adds this flag in
mac80211 for drivers that indicate to support pulling packets from the
internal TXQ in mac80211. I found it is deprecated, but as Felix
mentioned it is used in various parts of the network subsystem, ie.
batman-adv, bridge, vlan, tunnel implementations. So its use seems to be
restricted rather than deprecated. Given your response above I guess my
question would be to get details about what you call "proper design" as
I think you are saying with that it is not needed, right?
Regards,
Arend
next prev parent reply other threads:[~2019-04-16 8:04 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-16 17:06 [PATCH 1/5] mac80211: mesh: drop redundant rcu_read_lock/unlock calls Felix Fietkau
2019-03-16 17:06 ` [PATCH 2/5] mac80211: fix memory accounting with A-MSDU aggregation Felix Fietkau
2019-03-16 18:12 ` Toke Høiland-Jørgensen
2019-03-16 17:06 ` [PATCH 3/5] mac80211: calculate hash for fq without holding fq->lock in itxq enqueue Felix Fietkau
2019-03-16 18:13 ` Toke Høiland-Jørgensen
2019-03-16 17:06 ` [PATCH 4/5] mac80211: run late dequeue late tx handlers without holding fq->lock Felix Fietkau
2019-03-16 18:13 ` Toke Høiland-Jørgensen
2022-12-05 9:46 ` Wen Gong
2022-12-07 6:30 ` Wen Gong
2022-12-12 8:31 ` Wen Gong
2019-03-16 17:06 ` [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues Felix Fietkau
2019-03-16 18:14 ` Toke Høiland-Jørgensen
2019-04-14 9:44 ` Arend Van Spriel
2019-04-14 11:19 ` Felix Fietkau
2019-04-14 12:34 ` Arend Van Spriel
2019-04-16 7:34 ` Arend Van Spriel
2019-04-16 7:44 ` Herbert Xu
2019-04-16 8:04 ` Arend Van Spriel [this message]
2019-04-16 8:36 ` Herbert Xu
2019-04-16 8:37 ` Johannes Berg
2019-04-16 9:17 ` Arend Van Spriel
2019-04-16 9:29 ` Herbert Xu
2019-04-16 9:33 ` Toke Høiland-Jørgensen
2019-04-16 9:33 ` Johannes Berg
2019-04-16 9:37 ` Herbert Xu
2019-04-16 9:39 ` Johannes Berg
2019-04-16 10:02 ` Toke Høiland-Jørgensen
2019-04-17 2:11 ` Herbert Xu
2019-04-17 8:28 ` Toke Høiland-Jørgensen
2019-04-16 13:13 ` Herbert Xu
2019-04-16 13:18 ` Toke Høiland-Jørgensen
2019-04-17 3:38 ` Herbert Xu
2019-04-17 9:09 ` Toke Høiland-Jørgensen
2019-04-17 9:16 ` Arend Van Spriel
2019-04-17 9:17 ` Toke Høiland-Jørgensen
2019-04-23 12:41 ` Johannes Berg
2019-04-25 8:35 ` Herbert Xu
2019-04-25 8:39 ` Johannes Berg
2019-04-25 8:44 ` Herbert Xu
2019-04-25 8:49 ` Johannes Berg
2019-04-16 19:13 ` Johannes Berg
2019-04-17 2:13 ` Herbert Xu
2019-04-16 9:38 ` Toke Høiland-Jørgensen
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