linux-kernel - Re: [PATCH net 3/3] net: mvpp2: do not call txq_done from the Tx path when Tx irqs are used

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Message-Id: <20171024.183458.1613489746739108710.davem@davemloft.net>
Date:   Tue, 24 Oct 2017 18:34:58 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     antoine.tenart@...e-electrons.com
Cc:     andrew@...n.ch, gregory.clement@...e-electrons.com,
        thomas.petazzoni@...e-electrons.com,
        miquel.raynal@...e-electrons.com, nadavh@...vell.com,
        linux-kernel@...r.kernel.org, mw@...ihalf.com, stefanc@...vell.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net 3/3] net: mvpp2: do not call txq_done from the Tx
 path when Tx irqs are used

From: Antoine Tenart <antoine.tenart@...e-electrons.com>
Date: Mon, 23 Oct 2017 15:24:31 +0200

> When Tx IRQs are used, txq_bufs_free() can be called from both the Tx
> path and from NAPI poll(). This led to CPU stalls as if these two tasks
> (Tx and Poll) are scheduled on two CPUs at the same time, DMA unmapping
> operations are done on the same txq buffers.
> 
> This patch adds a check not to call txq_done() from the Tx path if Tx
> interrupts are used as it does not make sense to do so.
> 
> Fixes: edc660fa09e2 ("net: mvpp2: replace TX coalescing interrupts with hrtimer")
> Signed-off-by: Antoine Tenart <antoine.tenart@...e-electrons.com>

Applied.