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Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let ksoftirqd do its job"

From Brian Starkey <brian.starkey@arm.com>
Newsgroups linux.kernel
Subject Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let ksoftirqd do its job"
Date 2016-11-16 22:10 +0100
Message-ID <sEfCV-87c-1@gated-at.bofh.it> (permalink)
References <sE8UP-3xZ-65@gated-at.bofh.it> <sEaMV-4Od-7@gated-at.bofh.it> <sEcOJ-6ob-3@gated-at.bofh.it> <sEdrs-6BG-23@gated-at.bofh.it>
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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

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Thread

Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-16 15:00 +0100
  Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Eric Dumazet <edumazet@google.com> - 2016-11-16 17:00 +0100
    Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-16 19:10 +0100
      Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Eric Dumazet <edumazet@google.com> - 2016-11-16 19:50 +0100
        Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-16 22:10 +0100
          Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-17 18:10 +0100
            Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Thomas Gleixner <tglx@linutronix.de> - 2016-11-18 01:50 +0100
              Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-18 21:30 +0100
              Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-22 11:40 +0100
                Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Eric Dumazet <edumazet@google.com> - 2016-11-22 15:30 +0100
                Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-22 16:30 +0100
                Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Eric Dumazet <edumazet@google.com> - 2016-11-22 17:20 +0100
                Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Brian Starkey <brian.starkey@arm.com> - 2016-11-23 19:30 +0100
                Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Eric Dumazet <edumazet@google.com> - 2016-11-23 21:10 +0100
          Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let  ksoftirqd do its job" Eric Dumazet <edumazet@google.com> - 2016-11-17 18:10 +0100

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