From: Eric Dumazet <eric.dumazet@gmail.com>
To: Finn Thain <fthain@telegraphics.com.au>
Cc: "David S. Miller" <davem@davemloft.net>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Chris Zankel <chris@zankel.net>,
Laurent Vivier <laurent@vivier.eu>,
Geert Uytterhoeven <geert@linux-m68k.org>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net v2 01/12] net/sonic: Add mutual exclusion for accessing shared state
Date: Tue, 21 Jan 2020 15:52:58 -0800 [thread overview]
Message-ID: <1b8d9cbe-94cf-2eb6-de44-2a2f9cb0a084@gmail.com> (raw)
In-Reply-To: <alpine.LNX.2.21.1.2001221021590.8@nippy.intranet>
On 1/21/20 3:33 PM, Finn Thain wrote:
> On Tue, 21 Jan 2020, Eric Dumazet wrote:
>
>> On 1/21/20 1:22 PM, Finn Thain wrote:
>>> The netif_stop_queue() call in sonic_send_packet() races with the
>>> netif_wake_queue() call in sonic_interrupt(). This causes issues
>>> like "NETDEV WATCHDOG: eth0 (macsonic): transmit queue 0 timed out".
>>> Fix this by disabling interrupts when accessing tx_skb[] and next_tx.
>>> Update a comment to clarify the synchronization properties.
>>>
>>> Fixes: efcce839360f ("[PATCH] macsonic/jazzsonic network drivers update")
>>> Tested-by: Stan Johnson <userm57@yahoo.com>
>>> Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
>>
>>> @@ -284,9 +287,16 @@ static irqreturn_t sonic_interrupt(int irq, void *dev_id)
>>> struct net_device *dev = dev_id;
>>> struct sonic_local *lp = netdev_priv(dev);
>>> int status;
>>> + unsigned long flags;
>>> +
>>> + spin_lock_irqsave(&lp->lock, flags);
>>
>>
>> This is a hard irq handler, no need to block hard irqs.
>>
>> spin_lock() here is enough.
>>
>
> Well, yes, assuming we're dealing with SMP [1]. Probably just disabling
> pre-emption is all that will ever be needed.
>
> Anyway, the real problem solved by disabling irqs is that macsonic must
> avoid re-entrance of sonic_interrupt(). [2]
>
> [1]
> https://lore.kernel.org/netdev/alpine.LNX.2.21.1.2001211026190.8@nippy.intranet/T/#m0523c8b2a26a410ed56889d9230c37ba1160d40a
>
> [2]
> https://lore.kernel.org/netdev/alpine.LNX.2.21.1.2001211026190.8@nippy.intranet/T/#m1c8ca580d2b45e61a628d17839978d0bd5aaf061
>
Oh well...
I would rather keep the m68k specific wrapper...
Please add a fat comment of why spin_lock_irqsave() is used,
to avoid a future 'cleanup', since average network developer
wont be aware of m68k oddities.
next prev parent reply other threads:[~2020-01-21 23:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 21:22 [PATCH net v2 00/12] Fixes for SONIC ethernet driver Finn Thain
2020-01-21 21:22 ` [PATCH net v2 11/12] net/sonic: Fix CAM initialization Finn Thain
2020-01-21 21:22 ` [PATCH net v2 10/12] net/sonic: Fix command register usage Finn Thain
2020-01-21 21:22 ` [PATCH net v2 04/12] net/sonic: Fix interface error stats collection Finn Thain
2020-01-21 21:22 ` [PATCH net v2 07/12] net/sonic: Improve receive descriptor status flag check Finn Thain
2020-01-21 21:22 ` [PATCH net v2 02/12] net/sonic: Clear interrupt flags immediately Finn Thain
2020-01-21 21:22 ` [PATCH net v2 05/12] net/sonic: Fix receive buffer handling Finn Thain
2020-01-21 22:23 ` Stephen Hemminger
2020-01-21 23:53 ` Finn Thain
2020-01-21 21:22 ` [PATCH net v2 06/12] net/sonic: Avoid needless receive descriptor EOL flag updates Finn Thain
2020-01-21 21:22 ` [PATCH net v2 03/12] net/sonic: Use MMIO accessors Finn Thain
2020-01-21 21:22 ` [PATCH net v2 12/12] net/sonic: Prevent tx watchdog timeout Finn Thain
2020-01-21 21:22 ` [PATCH net v2 01/12] net/sonic: Add mutual exclusion for accessing shared state Finn Thain
2020-01-21 22:19 ` Eric Dumazet
2020-01-21 23:33 ` Finn Thain
2020-01-21 23:52 ` Eric Dumazet [this message]
2020-01-22 0:40 ` Finn Thain
2020-01-21 21:22 ` [PATCH net v2 09/12] net/sonic: Quiesce SONIC before re-initializing descriptor memory Finn Thain
2020-01-21 21:22 ` [PATCH net v2 08/12] net/sonic: Fix receive buffer replenishment Finn Thain
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