From: Brian Starkey <brian.starkey@arm.com>
To: Eric Dumazet <edumazet@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Potapenko <glider@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let ksoftirqd do its job"
Date: Wed, 16 Nov 2016 21:01:40 +0000 [thread overview]
Message-ID: <20161116210139.GB21156@e106950-lin.cambridge.arm.com> (raw)
In-Reply-To: <CANn89iK=yTkVKi9Wnx3ZXWZSOQc6KJT-FcE7H-5+QB85GE4=Vw@mail.gmail.com>
On Wed, Nov 16, 2016 at 10:49:06AM -0800, Eric Dumazet wrote:
>On Wed, Nov 16, 2016 at 10:01 AM, Brian Starkey <brian.starkey@arm.com> wrote:
>
>>
>> The smc91x driver does seem to have some trickiness around softirqs.
>> I'm not familiar with net drivers, but I'll see if I can figure
>> anything out there.
>
>Oh this code looks ugly :(
>
>Do you have CONFIG_SMP=y or not ?
Yeah CONFIG_SMP=y (and CONFIG_PREEMPT=y too, fwiw).
I did try forcing it into the no-op locking (as though config SMP
wasn't set), it didn't help (and it doesn't look like that would be
safe with CONFIG_PREEMPT=y either).
The bit in smc_hardware_send_pkt looks like skipping softirq
invocation when there's already one running wouldn't give the same
behaviour as before:
if (!smc_special_trylock(&lp->lock, flags)) {
netif_stop_queue(dev);
tasklet_schedule(&lp->tx_task);
return;
}
... that said, I've no idea if that matters.
Of course I also don't know if the network driver is even to blame :-(
Cheers,
-Brian
next prev parent reply other threads:[~2016-11-16 21:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 13:55 Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let ksoftirqd do its job" Brian Starkey
2016-11-16 15:52 ` Eric Dumazet
2016-11-16 18:01 ` Brian Starkey
2016-11-16 18:49 ` Eric Dumazet
2016-11-16 21:01 ` Brian Starkey [this message]
2016-11-17 15:29 ` Eric Dumazet
2016-11-17 16:42 ` Brian Starkey
2016-11-18 0:40 ` Thomas Gleixner
2016-11-18 20:23 ` Brian Starkey
2016-11-22 10:33 ` Brian Starkey
2016-11-22 14:29 ` Eric Dumazet
2016-11-22 15:27 ` Brian Starkey
2016-11-22 16:09 ` Eric Dumazet
2016-11-23 18:21 ` Brian Starkey
2016-11-23 20:03 ` Eric Dumazet
2016-11-25 13:14 ` Brian Starkey
2017-02-06 18:46 ` Will Deacon
2017-02-06 18:49 ` Russell King - ARM Linux
2017-02-08 9:46 ` Will Deacon
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