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From:   Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To:     tglx@linutronix.de
Cc:     Jisheng.Zhang@synaptics.com, afzal.mohd.ma@gmail.com,
        akpm@linux-foundation.org, corbet@lwn.net, gpiccoli@canonical.com,
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        mike.kravetz@oracle.com, mkshah@codeaurora.org, oneukum@suse.com,
        pawan.kumar.gupta@linux.intel.com, peterz@infradead.org,
        pmladek@suse.com, viro@zeniv.linux.org.uk,
        Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Subject: Re: [PATCH 0/3] warn and suppress irqflood
Date:   Tue,  2 Mar 2021 13:15:56 +0530
Message-Id: <20210302074556.23998-1-saiprakash.ranjan@codeaurora.org>
In-Reply-To: <87tuueftou.fsf@nanos.tec.linutronix.de>
References: <87tuueftou.fsf@nanos.tec.linutronix.de>
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Hi Thomas,

> On Wed, Oct 28, 2020 at 12:58:41PM +0100, Thomas Gleixner wrote:
>

<snip>...

> Something like the completly untested below should work independent of
> config options.
> 
> Thanks,
> 
>         tglx
> ---
>  include/linux/irqdesc.h |    4 ++
>  kernel/irq/manage.c     |    3 +
>  kernel/irq/spurious.c   |   74 +++++++++++++++++++++++++++++++++++-------------
>  3 files changed, 61 insertions(+), 20 deletions(-)
> 
> --- a/include/linux/irqdesc.h
> +++ b/include/linux/irqdesc.h
> @@ -30,6 +30,8 @@ struct pt_regs;
>   * @tot_count:		stats field for non-percpu irqs
>   * @irq_count:		stats field to detect stalled irqs
>   * @last_unhandled:	aging timer for unhandled count
> + * @storm_count:	Counter for irq storm detection
> + * @storm_checked:	Timestamp for irq storm detection
>   * @irqs_unhandled:	stats field for spurious unhandled interrupts
>   * @threads_handled:	stats field for deferred spurious detection of threaded handlers
>   * @threads_handled_last: comparator field for deferred spurious detection of theraded handlers
> @@ -65,6 +67,8 @@ struct irq_desc {
>  	unsigned int		tot_count;
>  	unsigned int		irq_count;	/* For detecting broken IRQs */
>  	unsigned long		last_unhandled;	/* Aging timer for unhandled count */
> +	unsigned long		storm_count;
> +	unsigned long		storm_checked;
>  	unsigned int		irqs_unhandled;
>  	atomic_t		threads_handled;
>  	int			threads_handled_last;
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1581,6 +1581,9 @@ static int
>  	if (!shared) {
>  		init_waitqueue_head(&desc->wait_for_threads);
>  
> +		/* Take a timestamp for interrupt storm detection */
> +		desc->storm_checked = jiffies;
> +
>  		/* Setup the type (level, edge polarity) if configured: */
>  		if (new->flags & IRQF_TRIGGER_MASK) {
>  			ret = __irq_set_trigger(desc,
> --- a/kernel/irq/spurious.c
> +++ b/kernel/irq/spurious.c
> @@ -21,6 +21,7 @@ static void poll_spurious_irqs(struct ti
>  static DEFINE_TIMER(poll_spurious_irq_timer, poll_spurious_irqs);
>  static int irq_poll_cpu;
>  static atomic_t irq_poll_active;
> +static unsigned long irqstorm_limit __ro_after_init;
>  
>  /*
>   * We wait here for a poller to finish.
> @@ -189,18 +190,21 @@ static inline int bad_action_ret(irqretu
>   * (The other 100-of-100,000 interrupts may have been a correctly
>   *  functioning device sharing an IRQ with the failing one)
>   */
> -static void __report_bad_irq(struct irq_desc *desc, irqreturn_t action_ret)
> +static void __report_bad_irq(struct irq_desc *desc, irqreturn_t action_ret,
> +			     bool storm)
>  {
>  	unsigned int irq = irq_desc_get_irq(desc);
>  	struct irqaction *action;
>  	unsigned long flags;
>  
> -	if (bad_action_ret(action_ret)) {
> -		printk(KERN_ERR "irq event %d: bogus return value %x\n",
> -				irq, action_ret);
> -	} else {
> -		printk(KERN_ERR "irq %d: nobody cared (try booting with "
> +	if (!storm) {
> +		if (bad_action_ret(action_ret)) {
> +			pr_err("irq event %d: bogus return value %x\n",
> +			       irq, action_ret);
> +		} else {
> +			pr_err("irq %d: nobody cared (try booting with "
>  				"the \"irqpoll\" option)\n", irq);
> +		}
>  	}
>  	dump_stack();
>  	printk(KERN_ERR "handlers:\n");
> @@ -228,7 +232,7 @@ static void report_bad_irq(struct irq_de
>  
>  	if (count > 0) {
>  		count--;
> -		__report_bad_irq(desc, action_ret);
> +		__report_bad_irq(desc, action_ret, false);
>  	}
>  }
>  
> @@ -267,6 +271,33 @@ try_misrouted_irq(unsigned int irq, stru
>  	return action && (action->flags & IRQF_IRQPOLL);
>  }
>  
> +static void disable_stuck_irq(struct irq_desc *desc, irqreturn_t action_ret,
> +			      const char *reason, bool storm)
> +{
> +	__report_bad_irq(desc, action_ret, storm);
> +	pr_emerg("Disabling %s IRQ #%d\n", reason, irq_desc_get_irq(desc));
> +	desc->istate |= IRQS_SPURIOUS_DISABLED;
> +	desc->depth++;
> +	irq_disable(desc);
> +}
> +
> +/* Interrupt storm detector for runaway interrupts (handled or not). */
> +static bool irqstorm_detected(struct irq_desc *desc)
> +{
> +	unsigned long now = jiffies;
> +
> +	if (++desc->storm_count < irqstorm_limit) {
> +		if (time_after(now, desc->storm_checked + HZ)) {
> +			desc->storm_count = 0;
> +			desc->storm_checked = now;
> +		}
> +		return false;
> +	}
> +
> +	disable_stuck_irq(desc, IRQ_NONE, "runaway", true);
> +	return true;
> +}
> +
>  #define SPURIOUS_DEFERRED	0x80000000
>  
>  void note_interrupt(struct irq_desc *desc, irqreturn_t action_ret)
> @@ -403,24 +434,16 @@ void note_interrupt(struct irq_desc *des
>  			desc->irqs_unhandled -= ok;
>  	}
>  
> +	if (unlikely(irqstorm_limit && irqstorm_detected(desc)))
> +		return;
> +
>  	desc->irq_count++;
>  	if (likely(desc->irq_count < 100000))
>  		return;
>  
>  	desc->irq_count = 0;
>  	if (unlikely(desc->irqs_unhandled > 99900)) {
> -		/*
> -		 * The interrupt is stuck
> -		 */
> -		__report_bad_irq(desc, action_ret);
> -		/*
> -		 * Now kill the IRQ
> -		 */
> -		printk(KERN_EMERG "Disabling IRQ #%d\n", irq);
> -		desc->istate |= IRQS_SPURIOUS_DISABLED;
> -		desc->depth++;
> -		irq_disable(desc);
> -
> +		disable_stuck_irq(desc, action_ret, "unhandled", false);
>  		mod_timer(&poll_spurious_irq_timer,
>  			  jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
>  	}
> @@ -462,5 +485,16 @@ static int __init irqpoll_setup(char *st
>  				"performance\n");
>  	return 1;
>  }
> -
>  __setup("irqpoll", irqpoll_setup);
> +
> +static int __init irqstorm_setup(char *arg)
> +{
> +	int res = kstrtoul(arg, 0, &irqstorm_limit);
> +
> +	if (!res) {
> +		pr_info("Interrupt storm detector enabled. Limit=%lu / s\n",
> +			irqstorm_limit);
> +	}
> +	return !!res;
> +}
> +__setup("irqstorm_limit", irqstorm_setup);

This irq storm detection feature is very useful, any chance to get this merged?
We will be happy to test. People seem to be having their own copy of such feature
out-of-tree [1].

[1] https://elinux.org/images/d/de/Oct28_InterruptStormDetectionFeature_KentoKobayashi.pdf

Thanks,
Sai
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