Date: Mon, 25 Feb 2013 22:41:54 -0700 From: PseudoCylon <moonlightakkiy@yahoo.ca> To: Adrian Chadd <adrian@freebsd.org> Cc: freebsd-wireless@freebsd.org Subject: Re: [RFT] net80211 TX serialisation, take #4 Message-ID: <CAFZ_MY%2B=O=-FtnYFqCfETmRk4UVvT-e0WChfNK9SnGtMbRu%2BWQ@mail.gmail.com> In-Reply-To: <CAJ-VmonwpUWdQdJARS-D5UfEr=F7CFLSyWeRsh-iXSa26m7uYQ@mail.gmail.com> References: <CAFZ_MYJ13f6cvL4rP2XrO2rP=odHJigis8EBcAF4r65-ATOxGw@mail.gmail.com> <CAJ-Vmon5p=3gbdnQ1dtCXNGO-=k-_-ZyTS6wuBAMArC-jmdfXw@mail.gmail.com> <CAFZ_MYK-RiCMZ6XUgkhyAWmyXAPDQXnX14YnmWEqDqhjrzpVjA@mail.gmail.com> <CAJ-VmonwpUWdQdJARS-D5UfEr=F7CFLSyWeRsh-iXSa26m7uYQ@mail.gmail.com>
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On Mon, Feb 25, 2013 at 12:27 AM, Adrian Chadd <adrian@freebsd.org> wrote:
> The trouble with using a queue is that things will dequeue frames out
> of order, bceause multiple dequeue contexts (ie, each call to
> driver_start / driver_transmit) will execute in-parallel.
Actually, to prevent that, there is an extra queue.
To begin
driver_queue:packet1--packet2--3--4--...
working_queue:empty
hadware_queue:empty
After multiple thread dequeue
lock dequeue enqueue unlock
lock dequeue enqueue unlock
They look like,
driver_queue:2--3--4--...
working_queue:1--2 (the lock preserves the order)
hardware_queue: empty
If a thread has packet #1 finished first, there is no problem.
If a thread has packet #2 finished first, it will try to dequeue the
packet #1 (head of the queue) from the working_queue. But the packet
isn't marked as "completed", so it will just return.
Queue still look like
driver_queue:2--3--4--...
(of course, other threads are processing remaining packets,
but to simplify, no change in driver_queue.)
working_queue: 1--2
hardware: empty
Later, once the thread with #1 finished processing, it will
lock while (completed) {dequeue enqueue} unlock
At the end, queue look like,
driver_queue:2--3--4--...
working_queue: empty
hardware_queue: 1--2 (the lock preserves the order)
Just wanted to clarify. I will soon test the latest txlock patch.
AK
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