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Date:	Sat, 26 Jul 2014 00:25:29 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [RFC][PATCH] irq: Rework IRQF_NO_SUSPENDED

On Friday, July 25, 2014 11:00:12 PM Thomas Gleixner wrote:
> On Fri, 25 Jul 2014, Rafael J. Wysocki wrote:
> > On Friday, July 25, 2014 03:25:41 PM Peter Zijlstra wrote:
> > > OK, so Rafael said there's devices that keep on raising their interrupt
> > > until they get attention. Ideally this won't happen because the device
> > > is suspended etc.. But I'm sure there's some broken piece of hardware
> > > out there that'll make it go boom.
> > 
> > So here's an idea.
> > 
> > What about returning IRQ_NONE rather than IRQ_HANDLED for "suspended"
> > interrupts (after all, that's what a sane driver would do for a
> > suspended device I suppose)?
> > 
> > If the line is really shared and the interrupt is taken care of by
> > the other guy sharing the line, we'll be all fine.
> > 
> > If that is not the case, on the other hand, and something's really
> > broken, we'll end up disabling the interrupt and marking it as
> > IRQS_SPURIOUS_DISABLED (if I understand things correctly).
> 
> We should not wait 100k unhandled interrupts in that case. We know
> already at the first unhandled interrupt that the shit hit the fan.

The first one may be a bus glitch or some such.  Also I guess we still need to
allow the legitimate "no suspend" guy to handle his interrupts until it gets
too worse.

Also does it really hurt to rely on the generic mechanism here?  We regard
it as fine at all other times after all.

> I'll have a deeper look how we can sanitize the whole wake/no_suspend
> logic vs. shared interrupts.

Cool, thanks!

> Need to look at the usage sites first.

There will be more of them, like this:

https://patchwork.kernel.org/patch/4618531/

Essentially, all wakeup interrupts will need at least one no_suspend irqaction
going forward.

Below is my take on this (untested) in case it is useful for anything.

It is targeted at the problematic case (that is, a shared interrupt with at least
one irqaction that has IRQF_NO_SUSPEND set and at least one that doesn't) only and
is not supposed to change behavior in the other cases (the do_irqaction thing
shamelessly stolen from the Peter's patch).  It drops the IRQD_WAKEUP_STATE check,
because that has the same problem with shared interrupts as no_suspend.

Rafael


---
 kernel/irq/handle.c |   21 ++++++++++++++++++---
 kernel/irq/manage.c |   30 +++++++++++++++++++++++++-----
 2 files changed, 43 insertions(+), 8 deletions(-)

Index: linux-pm/kernel/irq/manage.c
===================================================================
--- linux-pm.orig/kernel/irq/manage.c
+++ linux-pm/kernel/irq/manage.c
@@ -385,10 +385,23 @@ setup_affinity(unsigned int irq, struct
 void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
 {
 	if (suspend) {
-		if (!desc->action || (desc->action->flags & IRQF_NO_SUSPEND)
-		    || irqd_has_set(&desc->irq_data, IRQD_WAKEUP_STATE))
+		struct irqaction *action = desc->action;
+		unsigned int no_suspend, flags;
+
+		if (!action)
+			return;
+		no_suspend = IRQF_NO_SUSPEND;
+		flags = 0;
+		do {
+			no_suspend &= action->flags;
+			flags |= action->flags;
+			action = action->next;
+		} while (action);
+		if (no_suspend)
 			return;
 		desc->istate |= IRQS_SUSPENDED;
+		if (flags & IRQF_NO_SUSPEND)
+			return;
 	}
 
 	if (!desc->depth++)
@@ -446,7 +459,15 @@ EXPORT_SYMBOL(disable_irq);
 void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
 {
 	if (resume) {
-		if (!(desc->istate & IRQS_SUSPENDED)) {
+		if (desc->istate & IRQS_SUSPENDED) {
+			desc->istate &= ~IRQS_SUSPENDED;
+			if (desc->istate & IRQS_SPURIOUS_DISABLED) {
+				pr_err("WARNING! Unhandled events during suspend for IRQ %d\n", irq);
+				desc->istate &= ~IRQS_SPURIOUS_DISABLED;
+			} else if (desc->depth == 0) {
+				return;
+			}
+		} else {
 			if (!desc->action)
 				return;
 			if (!(desc->action->flags & IRQF_FORCE_RESUME))
@@ -454,7 +475,6 @@ void __enable_irq(struct irq_desc *desc,
 			/* Pretend that it got disabled ! */
 			desc->depth++;
 		}
-		desc->istate &= ~IRQS_SUSPENDED;
 	}
 
 	switch (desc->depth) {
@@ -1079,7 +1099,7 @@ __setup_irq(unsigned int irq, struct irq
 		 */
 
 #define IRQF_MISMATCH \
-	(IRQF_TRIGGER_MASK | IRQF_ONESHOT | IRQF_NO_SUSPEND)
+	(IRQF_TRIGGER_MASK | IRQF_ONESHOT)
 
 		if (!((old->flags & new->flags) & IRQF_SHARED) ||
 		    ((old->flags ^ new->flags) & IRQF_MISMATCH))
Index: linux-pm/kernel/irq/handle.c
===================================================================
--- linux-pm.orig/kernel/irq/handle.c
+++ linux-pm/kernel/irq/handle.c
@@ -131,6 +131,23 @@ void __irq_wake_thread(struct irq_desc *
 }
 
 irqreturn_t
+do_irqaction(struct irq_desc *desc, struct irqaction *action,
+	     unsigned int irq, void *dev_id)
+{
+	irqreturn_t ret;
+
+	if (unlikely((desc->istate & IRQS_SUSPENDED) &&
+		     !(action->flags & IRQF_NO_SUSPEND)))
+		return IRQ_NONE;
+
+	trace_irq_handler_entry(irq, action);
+	ret = action->handler(irq, dev_id);
+	trace_irq_handler_exit(irq, action, ret);
+
+	return ret;
+}
+
+irqreturn_t
 handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
 {
 	irqreturn_t retval = IRQ_NONE;
@@ -139,9 +156,7 @@ handle_irq_event_percpu(struct irq_desc
 	do {
 		irqreturn_t res;
 
-		trace_irq_handler_entry(irq, action);
-		res = action->handler(irq, action->dev_id);
-		trace_irq_handler_exit(irq, action, res);
+		res = do_irqaction(desc, action, irq, action->dev_id);
 
 		if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
 			      irq, action->handler))

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