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

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Message-ID: <87ldvkdtqn.fsf@kernel.org>
Date: Thu, 09 Jan 2025 15:03:44 +0200
From: Kalle Valo <kvalo@...nel.org>
To: Remi Pommarel <repk@...plefau.lt>
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

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.

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