linux-kernel - Re: [RESEND PATCH v3 0/2] Improve ath10k flush queue mechanism

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Message-ID: <Z3_Vk6doGyavKSea@pilgrim>
Date: Thu, 9 Jan 2025 14:56:35 +0100
From: Remi Pommarel <repk@...plefau.lt>
To: Kalle Valo <kvalo@...nel.org>
Cc: ath10k@...ts.infradead.org, linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jeff Johnson <jjohnson@...nel.org>,
	Cedric Veilleux <veilleux.cedric@...il.com>,
	Vasanthakumar Thiagarajan <quic_vthiagar@...cinc.com>
Subject: Re: [RESEND PATCH v3 0/2] Improve ath10k flush queue mechanism

On Thu, Jan 09, 2025 at 03:03:44PM +0200, Kalle Valo wrote:
> Remi Pommarel <repk@...plefau.lt> writes:
> 
> > It has been reported [0] that a 3-4 seconds (actually up to 5 sec) of
> > radio silence could be observed followed by the error below on ath10k
> > devices:
> >
> >  ath10k_pci 0000:04:00.0: failed to flush transmit queue (skip 0 ar-state 1): 0
> >
> > This is due to how the TX queues are flushed in ath10k. When a STA is
> > removed, mac80211 need to flush queues [1], but because ath10k does not
> > have a lightweight .flush_sta operation, ieee80211_flush_queues() is
> > called instead effectively blocking the whole queue during the drain
> > causing this radio silence. Also because ath10k_flush() waits for all
> > queued to be emptied, not only the flushed ones it could more easily
> > take up to 5 seconds to finish making the whole situation worst.
> >
> > The first patch of this series adds a .flush_sta operation to flush only
> > specific STA traffic avoiding the need to stop whole queues and should
> > be enough in itself to fix the reported issue.
> >
> > The second patch of this series is a proposal to improve ath10k_flush so
> > that it will be less likely to timeout waiting for non related queues to
> > drain.
> >
> > The abose kernel warning could still be observed (e.g. flushing a dead
> > STA) but should be now harmless.
> >
> > [0]: https://lore.kernel.org/all/CA+Xfe4FjUmzM5mvPxGbpJsF3SvSdE5_wgxvgFJ0bsdrKODVXCQ@mail.gmail.com/
> > [1]: commit 0b75a1b1e42e ("wifi: mac80211: flush queues on STA removal")
> 
> On what hardware and firmware did you test this? As they can behave very
> differently knowing that is really important.

This was tested on QCA9888 hw 2.0 10.4-3.10-00076.

Not sure to see how a different HW/FW could have prevented that though.

-- 
Remi