From: Alexander Wetzel <alexander@wetzel-home.de>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless@vger.kernel.org
Subject: Re: [RFC] mac80211: Switch all drivers over to iTXQs
Date: Fri, 8 Jul 2022 18:42:32 +0200 [thread overview]
Message-ID: <ba8e3ae1-70a9-e016-6c44-ae0c52f97e8e@wetzel-home.de> (raw)
In-Reply-To: <20220707143230.21686-1-alexander@wetzel-home.de>
> This patch is working for at least iwldvm. It exposes what seems to
> be an existing iwldvm driver bug, though. Driver and card continues
> to work, making that a minor side show for now. (I started to look into
> that a bit, maybe more about that in another mail later.)
> Initial tests are indicating comparable speeds in my setup for iwldvm,
> maybe trending to be a bit slower.
>
> For now I'm interested what I may have missed or what should be done
> differently, so we dare to merge it. I'll planning to run some more
> tests and use iwldvm with this patch on my main workstation for some
> days at least.
I followed up on the iwldvm driver issue.
The problem is, that the push API drivers are expecting that tx
immediately stops after calling ieee80211_stop_queue(). And this patch
breaks that.
For iwldvm this happens:
- the HW queues are getting full, iwldvm calls ieee80211_stop_queue()
- the (patched) mac80211 stops the queue but is not aborting the running
wake_tx_queue() tasklet. Which goes on to hand over skbs to the driver
- The driver runs out of the "internal reserve" hw buffers and starts to
add the new skbs to the overflow queue
- some hw buffers are reclaimed and the driver tries to process the skbs
in the overflow q
- For that it releases the internal lock for tx, assuming mac80211
stopped handing over skbs
- the still running wake_tx_queue() function from mac80211 hands over
the next skb, grapping the slot(s) intended to be used for the skbs in
the driver overflow queue.
- which breaks an iwlwifi internal rule how sequence numbers are mapped
to hw queue slots, causing the warning I got.
I'll fix that and send a new patch.
Alexander
next prev parent reply other threads:[~2022-07-08 16:42 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 14:32 [RFC] mac80211: Switch all drivers over to iTXQs Alexander Wetzel
2022-07-08 16:42 ` Alexander Wetzel [this message]
2022-07-08 21:11 ` Johannes Berg
2022-07-21 1:44 ` [mac80211] 722bb2177a: hwsim.ap_fragmentation_open.fail kernel test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ba8e3ae1-70a9-e016-6c44-ae0c52f97e8e@wetzel-home.de \
--to=alexander@wetzel-home.de \
--cc=johannes@sipsolutions.net \
--cc=linux-wireless@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).