Message-ID: <3637397.iCmFpOsayO@vostro.rjw.lan>
Date:	Sun, 27 Jul 2014 17:53:07 +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 Saturday, July 26, 2014 12:25:29 AM Rafael J. Wysocki wrote:
> 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.

Having considered this for some more time, I think that we need to address
the IRQF_NO_SUSPEND problem with shared interrupts regardless of what's
decided about the device wakeup and suspending interrupts, because (1) it's
already there (and the Peter's patch to add IRQF_NO_SUSPEND to "mismatch"
flags may break working systems that aren't even buggy, sorry for noticing
that so late) and (2) we'll need something like IRQF_NO_SUSPEND idependently
of wakeup anyway, for timers and things like the ACPI SCI.

Below is my attempt to do that based on the prototype I sent previously.
It contains a mechanism to disable IRQs generating spurious interrupts
during system suspend/resume faster, but otherwise works along the same
lines.

Rafael


---
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Subject: irq / PM: Fix IRQF_NO_SUSPEND problem with shared interrupts

Since __disable_irq() only checks IRQF_NO_SUSPEND for the first
irqaction in a given irq_desc, that value of that bit for the
first irqaction affects all of the other irqactions sharing the
interrupt with it.  This is problematic in two cases.

First, if IRQF_NO_SUSPEND is set in the first irqaction and unset
in at least one of the other irqactions sharing the same interrupt,
the interrupt handlers in the other irqactions with IRQF_NO_SUSPEND
unset will be invoked after suspend_device_irqs() has returned even
though they are not supposed to.  That shouldn't be a problem if
those interrupt handlers are implemented correctly and the
corresponding devices are properly suspended, but it may lead to
functional issues otherwise.

Second, if IRQF_NO_SUSPEND is unset in the first irqaction and set
in at least one of the other irqactions sharing the same interrupt,
the interrupt handlers in the other irqactions with IRQF_NO_SUSPEND
set will not be invoked after suspend_device_irqs() has returned, but
they are supposed to be invoked then.  That may be a problem if the
corresponding devices are wakeup devices or if their interrupts have
to be properly handled during system suspend/resume too for other
reasons, which is the case for timer interrupts or the ACPI SCI for
example.

To address this, modify the handling of IRQF_NO_SUSPEND by
suspend_device_irqs() and resume_device_irqs() and make
handle_irq_event_percpu() and note_interrupt() handle IRQS_SUSPENDED.

First of all, make suspend_device_irqs() check IRQF_NO_SUSPEND for
all irqactions sharing the same irq_desc and avoid disabling the IRQ
if at least one of them has IRQF_NO_SUSPEND unset.  If that flag
is set for at least one irqaction in the given irq_desc, however,
suspend_device_irqs() will stil mark the IRQ as IRQS_SUSPENDED.

Second, make handle_irq_event_percpu() return IRQ_NONE without
invoking the interrupt handler for irqactions with IRQF_NO_SUSPEND
unset if their irq_desc is marked as IRQS_SUSPENDED.

Next, modify note_interrupt() to disable misbehaving IRQs faster if
spuroius interrupts occur during system suspend/resume (that is, for
an irq_desc with IRQS_SUSPENDED set).

Finally, make resume_device_irqs() clear the IRQS_SPURIOUS_DISABLED
flag for IRQs that were emergency disabled after suspend_device_irqs()
had returned and log warning messages for them.

This should address the problematic case (when IRQF_NO_SUSPEND is set
for at least one and unset for at least one irqaction sharing one
irq_desc) and that case only without changing behavior in any other
cases.

It also effectively reverts a previous change to refuse interrupt
requests with IRQF_NO_SUSPEND settings that do not match the
existing ones (as it is not needed any more) and a previous change
that added a IRQD_WAKEUP_STATE check to __disable_irqs() (as that
mechanism has the same problem with shared interrupts as described
above).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 kernel/irq/handle.c   |   21 ++++++++++++++++++---
 kernel/irq/manage.c   |   31 ++++++++++++++++++++++++++-----
 kernel/irq/spurious.c |   27 ++++++++++++++++++---------
 3 files changed, 62 insertions(+), 17 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 || (desc->istate & IRQS_SPURIOUS_DISABLED))
+			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 +459,16 @@ 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("Re-enabling emergency disabled 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 +476,6 @@ void __enable_irq(struct irq_desc *desc,
 			/* Pretend that it got disabled ! */
 			desc->depth++;
 		}
-		desc->istate &= ~IRQS_SUSPENDED;
 	}
 
 	switch (desc->depth) {
@@ -1079,7 +1100,7 @@ __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))
Index: linux-pm/kernel/irq/spurious.c
===================================================================
--- linux-pm.orig/kernel/irq/spurious.c
+++ linux-pm/kernel/irq/spurious.c
@@ -275,6 +275,8 @@ try_misrouted_irq(unsigned int irq, stru
 void note_interrupt(unsigned int irq, struct irq_desc *desc,
 		    irqreturn_t action_ret)
 {
+	int misrouted;
+
 	if (desc->istate & IRQS_POLL_INPROGRESS ||
 	    irq_settings_is_polled(desc))
 		return;
@@ -384,6 +386,9 @@ void note_interrupt(unsigned int irq, st
 		}
 	}
 
+	misrouted = unlikely(try_misrouted_irq(irq, desc, action_ret)) ?
+			misrouted_irq(irq) : 0;
+
 	if (unlikely(action_ret == IRQ_NONE)) {
 		/*
 		 * If we are seeing only the odd spurious IRQ caused by
@@ -391,19 +396,23 @@ void note_interrupt(unsigned int irq, st
 		 * otherwise the counter becomes a doomsday timer for otherwise
 		 * working systems
 		 */
-		if (time_after(jiffies, desc->last_unhandled + HZ/10))
-			desc->irqs_unhandled = 1;
-		else
+		if (time_after(jiffies, desc->last_unhandled + HZ/10)) {
+			desc->irqs_unhandled = 1 - misrouted;
+		} else if (!misrouted) {
 			desc->irqs_unhandled++;
+			if (unlikely(desc->istate & IRQS_SUSPENDED)) {
+				/*
+				 * That shouldn't happen.  It means IRQs from
+				 * a device that is supposed to be suspended at
+				 * this point.  Decay faster.
+				 */
+				desc->irqs_unhandled += 999;
+				desc->irq_count += 999;
+			}
+		}
 		desc->last_unhandled = jiffies;
 	}
 
-	if (unlikely(try_misrouted_irq(irq, desc, action_ret))) {
-		int ok = misrouted_irq(irq);
-		if (action_ret == IRQ_NONE)
-			desc->irqs_unhandled -= ok;
-	}
-
 	desc->irq_count++;
 	if (likely(desc->irq_count < 100000))
 		return;

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