[PATCH, v6] irq / PM: Fix IRQF_NO_SUSPEND problem with shared interrupts

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

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
note_interrupt() handle suspended interrupts.

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 set.  If that flag is
also unset for at least one irqaction in the given irq_desc, however,
suspend_device_irqs() will move the irqactions with IRQF_NO_SUSPEND
unset over to a list of "suspended actions" whose interrupt handlers
won't be invoked going forward.

Second, 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() move irqactions from the list of
"suspended actions" created by suspend_device_irqs() back to the
regular "action" list.  It also will clear the IRQS_SPURIOUS_DISABLED
flag for IRQS_SUSPENDED IRQs that were emergency disabled after
suspend_device_irqs() had returned and will 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@xxxxxxxxx>
---

One more minor update, sorry about that.

I've just noticed that in v5 I used the same name (no_suspend) for two different
variables in the same function (in different scopes, but still confusing), so
this is fixed here.

Rafael

---
 include/linux/irqdesc.h |    2 +
 kernel/irq/internals.h  |    4 +-
 kernel/irq/manage.c     |   31 +++---------------
 kernel/irq/pm.c         |   82 ++++++++++++++++++++++++++++++++++++++++++++++--
 kernel/irq/spurious.c   |   14 +++++++-
 5 files changed, 102 insertions(+), 31 deletions(-)

Index: linux-pm/kernel/irq/manage.c
===================================================================
--- linux-pm.orig/kernel/irq/manage.c
+++ linux-pm/kernel/irq/manage.c
@@ -382,15 +382,8 @@ setup_affinity(unsigned int irq, struct
 }
 #endif
 
-void __disable_irq(struct irq_desc *desc, unsigned int irq, bool suspend)
+void __disable_irq(struct irq_desc *desc, unsigned int irq)
 {
-	if (suspend) {
-		if (!desc->action || (desc->action->flags & IRQF_NO_SUSPEND)
-		    || irqd_has_set(&desc->irq_data, IRQD_WAKEUP_STATE))
-			return;
-		desc->istate |= IRQS_SUSPENDED;
-	}
-
 	if (!desc->depth++)
 		irq_disable(desc);
 }
@@ -402,7 +395,7 @@ static int __disable_irq_nosync(unsigned
 
 	if (!desc)
 		return -EINVAL;
-	__disable_irq(desc, irq, false);
+	__disable_irq(desc, irq);
 	irq_put_desc_busunlock(desc, flags);
 	return 0;
 }
@@ -443,20 +436,8 @@ void disable_irq(unsigned int irq)
 }
 EXPORT_SYMBOL(disable_irq);
 
-void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
+void __enable_irq(struct irq_desc *desc, unsigned int irq)
 {
-	if (resume) {
-		if (!(desc->istate & IRQS_SUSPENDED)) {
-			if (!desc->action)
-				return;
-			if (!(desc->action->flags & IRQF_FORCE_RESUME))
-				return;
-			/* Pretend that it got disabled ! */
-			desc->depth++;
-		}
-		desc->istate &= ~IRQS_SUSPENDED;
-	}
-
 	switch (desc->depth) {
 	case 0:
  err_out:
@@ -498,7 +479,7 @@ void enable_irq(unsigned int irq)
 		 KERN_ERR "enable_irq before setup/request_irq: irq %u\n", irq))
 		goto out;
 
-	__enable_irq(desc, irq, false);
+	__enable_irq(desc, irq);
 out:
 	irq_put_desc_busunlock(desc, flags);
 }
@@ -1079,7 +1060,7 @@ __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))
@@ -1232,7 +1213,7 @@ __setup_irq(unsigned int irq, struct irq
 	 */
 	if (shared && (desc->istate & IRQS_SPURIOUS_DISABLED)) {
 		desc->istate &= ~IRQS_SPURIOUS_DISABLED;
-		__enable_irq(desc, irq, false);
+		__enable_irq(desc, irq);
 	}
 
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
Index: linux-pm/kernel/irq/spurious.c
===================================================================
--- linux-pm.orig/kernel/irq/spurious.c
+++ linux-pm/kernel/irq/spurious.c
@@ -391,10 +391,20 @@ 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))
+		if (time_after(jiffies, desc->last_unhandled + HZ/10)) {
 			desc->irqs_unhandled = 1;
-		else
+		} else {
 			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;
 	}
 
Index: linux-pm/include/linux/irqdesc.h
===================================================================
--- linux-pm.orig/include/linux/irqdesc.h
+++ linux-pm/include/linux/irqdesc.h
@@ -20,6 +20,7 @@ struct irq_desc;
  * @handle_irq:		highlevel irq-events handler
  * @preflow_handler:	handler called before the flow handler (currently used by sparc)
  * @action:		the irq action chain
+ * @action_suspended:	suspended irq action chain
  * @status:		status information
  * @core_internal_state__do_not_mess_with_it: core internal status information
  * @depth:		disable-depth, for nested irq_disable() calls
@@ -47,6 +48,7 @@ struct irq_desc {
 	irq_preflow_handler_t	preflow_handler;
 #endif
 	struct irqaction	*action;	/* IRQ action list */
+	struct irqaction	*action_suspended;
 	unsigned int		status_use_accessors;
 	unsigned int		core_internal_state__do_not_mess_with_it;
 	unsigned int		depth;		/* nested irq disables */
Index: linux-pm/kernel/irq/internals.h
===================================================================
--- linux-pm.orig/kernel/irq/internals.h
+++ linux-pm/kernel/irq/internals.h
@@ -63,8 +63,8 @@ enum {
 
 extern int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
 		unsigned long flags);
-extern void __disable_irq(struct irq_desc *desc, unsigned int irq, bool susp);
-extern void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume);
+extern void __disable_irq(struct irq_desc *desc, unsigned int irq);
+extern void __enable_irq(struct irq_desc *desc, unsigned int irq);
 
 extern int irq_startup(struct irq_desc *desc, bool resend);
 extern void irq_shutdown(struct irq_desc *desc);
Index: linux-pm/kernel/irq/pm.c
===================================================================
--- linux-pm.orig/kernel/irq/pm.c
+++ linux-pm/kernel/irq/pm.c
@@ -13,6 +13,50 @@
 
 #include "internals.h"
 
+static void suspend_irq(struct irq_desc *desc, int irq)
+{
+	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) &&
+	    !(desc->istate & IRQS_SPURIOUS_DISABLED)) {
+		struct irqaction *active = NULL;
+		struct irqaction *suspended = NULL;
+		struct irqaction *head = desc->action;
+
+		do {
+			action = head;
+			head = action->next;
+			if (action->flags & IRQF_NO_SUSPEND) {
+				action->next = active;
+				active = action;
+			} else {
+				action->next = suspended;
+				suspended = action;
+			}
+		} while (head);
+		desc->action = active;
+		desc->action_suspended = suspended;
+		return;
+	}
+	__disable_irq(desc, irq);
+}
+
 /**
  * suspend_device_irqs - disable all currently enabled interrupt lines
  *
@@ -30,7 +74,7 @@ void suspend_device_irqs(void)
 		unsigned long flags;
 
 		raw_spin_lock_irqsave(&desc->lock, flags);
-		__disable_irq(desc, irq, true);
+		suspend_irq(desc, irq);
 		raw_spin_unlock_irqrestore(&desc->lock, flags);
 	}
 
@@ -40,6 +84,40 @@ void suspend_device_irqs(void)
 }
 EXPORT_SYMBOL_GPL(suspend_device_irqs);
 
+static void resume_irq(struct irq_desc *desc, int irq)
+{
+	if (desc->istate & IRQS_SUSPENDED) {
+		desc->istate &= ~IRQS_SUSPENDED;
+		if (desc->action_suspended) {
+			struct irqaction *action = desc->action;
+
+			while (action->next)
+				action = action->next;
+
+			action->next = desc->action_suspended;
+			desc->action_suspended = NULL;
+
+			if (desc->istate & IRQS_SPURIOUS_DISABLED) {
+				pr_err("Re-enabling emergency disabled IRQ %d\n",
+				       irq);
+				desc->istate &= ~IRQS_SPURIOUS_DISABLED;
+			} else {
+				return;
+			}
+		}
+	} else {
+		if (!desc->action)
+			return;
+
+		if (!(desc->action->flags & IRQF_FORCE_RESUME))
+			return;
+
+		/* Pretend that it got disabled ! */
+		desc->depth++;
+	}
+	__enable_irq(desc, irq);
+}
+
 static void resume_irqs(bool want_early)
 {
 	struct irq_desc *desc;
@@ -54,7 +132,7 @@ static void resume_irqs(bool want_early)
 			continue;
 
 		raw_spin_lock_irqsave(&desc->lock, flags);
-		__enable_irq(desc, irq, true);
+		resume_irq(desc, irq);
 		raw_spin_unlock_irqrestore(&desc->lock, flags);
 	}
 }

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