netdev - Re: [PATCH v2 1/2] rt2x00usb: fix rx queue hang

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Message-ID: <20190701110733.GA13992@redhat.com>
Date:   Mon, 1 Jul 2019 13:07:34 +0200
From:   Stanislaw Gruszka <sgruszka@...hat.com>
To:     Soeren Moch <smoch@....de>
Cc:     stable@...r.kernel.org, Helmut Schaa <helmut.schaa@...glemail.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] rt2x00usb: fix rx queue hang

On Mon, Jul 01, 2019 at 12:53:13PM +0200, Soeren Moch wrote:
> Since commit ed194d136769 ("usb: core: remove local_irq_save() around
>  ->complete() handler") the handler rt2x00usb_interrupt_rxdone() is
> not running with interrupts disabled anymore. So this completion handler
> is not guaranteed to run completely before workqueue processing starts
> for the same queue entry.
> Be sure to set all other flags in the entry correctly before marking
> this entry ready for workqueue processing. This way we cannot miss error
> conditions that need to be signalled from the completion handler to the
> worker thread.
> Note that rt2x00usb_work_rxdone() processes all available entries, not
> only such for which queue_work() was called.
> 
> This patch is similar to what commit df71c9cfceea ("rt2x00: fix order
> of entry flags modification") did for TX processing.
> 
> This fixes a regression on a RT5370 based wifi stick in AP mode, which
> suddenly stopped data transmission after some period of heavy load. Also
> stopping the hanging hostapd resulted in the error message "ieee80211
> phy0: rt2x00queue_flush_queue: Warning - Queue 14 failed to flush".
> Other operation modes are probably affected as well, this just was
> the used testcase.
> 
> Fixes: ed194d136769 ("usb: core: remove local_irq_save() around ->complete() handler")
> Cc: stable@...r.kernel.org # 4.20+
> Signed-off-by: Soeren Moch <smoch@....de>

Acked-by: Stanislaw Gruszka <sgruszka@...hat.com>