From: Francois Romieu <romieu@fr.zoreil.com>
To: Jia-Ju Bai <baijiaju1990@gmail.com>
Cc: nic_swsd@realtek.com, alexander.h.duyck@redhat.com,
David Miller <davem@davemloft.net>,
dhowells@redhat.com, paulmck@linux.vnet.ibm.com,
will.deacon@arm.com, peterz@infradead.org,
netdev@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: net: r8169: a question of memory barrier in the r8169 driver
Date: Fri, 19 Jan 2018 02:11:01 +0100 [thread overview]
Message-ID: <20180119011101.GA15920@electric-eye.fr.zoreil.com> (raw)
In-Reply-To: <9a373156-41e5-a78b-cd31-c4b9bdba2696@gmail.com>
Jia-Ju Bai <baijiaju1990@gmail.com> :
[...]
> The function rtl8169_start_xmit reads tp->dirty_tx in TX_FRAGS_READY_FOR:
> if (unlikely(!TX_FRAGS_READY_FOR(tp, skb_shinfo(skb)->nr_frags))) {
> netif_err(tp, drv, dev, "BUG! Tx Ring full when queue awake!\n");
> goto err_stop_0;
> }
> But there is no memory barrier around this code.
>
> Is there a possible data race here?
This code would not even be needed if rtl8169_start_xmit was only your
usual ndo_start_xmit handler: Realtek {ab / re}used it for GSO handling
(see r8169_csum_workaround).
If the test is not a no-op in this GSO context, it's racy.
--
Ueimor
next prev parent reply other threads:[~2018-01-19 1:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-18 14:06 Jia-Ju Bai
2018-01-18 15:06 ` Peter Zijlstra
2018-01-19 1:11 ` Francois Romieu
2018-01-19 17:14 ` Peter Zijlstra
2018-01-20 0:00 ` Francois Romieu
2018-01-19 1:11 ` Francois Romieu [this message]
2018-01-19 1:24 ` Jia-Ju Bai
2018-01-19 23:59 ` Francois Romieu
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