[PATCH] irq: add IRQF_RESUME_EARLY and resume such IRQs earlier in the process

[Ian Campbell]

This adds a mechanism to resume selected IRQs during syscore_resume instead of
dpm_resume_noirq.

Under Xen we need to resume IRQs associated with IPIs earlier enough that the
resched ipi is unmasked and we can therefore schedule ourselves out of the
stop_machine where the suspend/resume takes place.

This issue was introduced by 676dc3cf5bc3 "xen: Use IRQF_FORCE_RESUME".

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx (at least to 2.6.32.y)
---
 drivers/xen/events.c      |    2 +-
 include/linux/interrupt.h |    2 ++
 kernel/irq/pm.c           |   38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 41 insertions(+), 1 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 7523719..44490de 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1021,7 +1021,7 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
 	if (irq < 0)
 		return irq;
 
-	irqflags |= IRQF_NO_SUSPEND | IRQF_FORCE_RESUME;
+	irqflags |= IRQF_NO_SUSPEND | IRQF_FORCE_RESUME | IRQF_EARLY_RESUME;
 	retval = request_irq(irq, handler, irqflags, devname, dev_id);
 	if (retval != 0) {
 		unbind_from_irq(irq);
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index a103732..a3b8baa 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -59,6 +59,7 @@
  * IRQF_NO_SUSPEND - Do not disable this IRQ during suspend
  * IRQF_FORCE_RESUME - Force enable it on resume even if IRQF_NO_SUSPEND is set
  * IRQF_NO_THREAD - Interrupt cannot be threaded
+ * IRQF_EARLY_RESUME - Resume IRQ early during syscore instead of at device resume time
  */
 #define IRQF_DISABLED		0x00000020
 #define IRQF_SAMPLE_RANDOM	0x00000040
@@ -72,6 +73,7 @@
 #define IRQF_NO_SUSPEND		0x00004000
 #define IRQF_FORCE_RESUME	0x00008000
 #define IRQF_NO_THREAD		0x00010000
+#define IRQF_EARLY_RESUME	0x00020000
 
 #define IRQF_TIMER		(__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
 
diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
index f76fc00..4fbfb36 100644
--- a/kernel/irq/pm.c
+++ b/kernel/irq/pm.c
@@ -9,6 +9,7 @@
 #include <linux/irq.h>
 #include <linux/module.h>
 #include <linux/interrupt.h>
+#include <linux/syscore_ops.h>
 
 #include "internals.h"
 
@@ -40,6 +41,40 @@ void suspend_device_irqs(void)
 EXPORT_SYMBOL_GPL(suspend_device_irqs);
 
 /**
+ * irq_pm_syscore_ops - enable interrupt lines early
+ *
+ * Enable all interrupt lines with %IRQF_EARLY_RESUME set
+ */
+static void irq_pm_syscore_resume(void)
+{
+	struct irq_desc *desc;
+	int irq;
+
+	for_each_irq_desc(irq, desc) {
+		unsigned long flags;
+
+		if (!desc->action || !(desc->action->flags & IRQF_EARLY_RESUME))
+			continue;
+
+		raw_spin_lock_irqsave(&desc->lock, flags);
+		__enable_irq(desc, irq, true);
+		raw_spin_unlock_irqrestore(&desc->lock, flags);
+	}
+}
+
+static struct syscore_ops irq_pm_syscore_ops = {
+	.resume		= irq_pm_syscore_resume,
+};
+
+static int __init irq_pm_init_ops(void)
+{
+	register_syscore_ops(&irq_pm_syscore_ops);
+	return 0;
+}
+
+device_initcall(irq_pm_init_ops);
+
+/**
  * resume_device_irqs - enable interrupt lines disabled by suspend_device_irqs()
  *
  * Enable all interrupt lines previously disabled by suspend_device_irqs() that
@@ -53,6 +88,9 @@ void resume_device_irqs(void)
 	for_each_irq_desc(irq, desc) {
 		unsigned long flags;
 
+		if (desc->action && desc->action->flags & IRQF_EARLY_RESUME)
+			continue;
+
 		raw_spin_lock_irqsave(&desc->lock, flags);
 		__enable_irq(desc, irq, true);
 		raw_spin_unlock_irqrestore(&desc->lock, flags);
-- 
1.7.2.5



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