Re: [PATCH 1/3] irq / PM: New driver interface for wakeup interruptsn

Rafael J. Wysocki
2014-08-04T03:19:30Z

On Sunday, August 03, 2014 03:42:49 PM Rafael J. Wysocki wrote:
> On Saturday, August 02, 2014 03:31:01 AM Rafael J. Wysocki wrote:
> > On Friday, August 01, 2014 04:29:40 PM Rafael J. Wysocki wrote:
> > > On Friday, August 01, 2014 03:43:21 PM Thomas Gleixner wrote:
> > > > On Fri, 1 Aug 2014, Rafael J. Wysocki wrote:
> > > > > OK, I guess "IRQ_HANDLED from a wakeup interrupt" may be interpreted as
> > > > > IRQ_HANDLED_PMWAKE. On the other hand, if that's going to be handled in
> > > > > handle_irq_event_percpu(), then using a special return code would save us
> > > > > a brach for IRQ_HANDLED interrupts. We could convert it to IRQ_HANDLED
> > > > > immediately then.
> > > >
> > > > We can handle it at the end of the function by calling
> > > > note_interrupt() unconditionally do the following there:
> > > >
> > > > if (suspended) {
> > > > if (ret == IRQ_NONE) {
> > > > if (shared)
> > > > yell_and_abort_or_resume();
> > > > } else {
> > > > abort_or_resume();
> > > > }
> > > > }
> > > > if (noirqdebug)
> > > > return;
> > >
> > > I see.
> > >
> > > > > OK, I'll take a stab at the IRQF_SHARED thing if you don't mind.
> > > >
> > > > Definitely not :)
> > > >
> > > > > Here's my current understanding of what can be done for IRQF_NO_SUSPEND.
> > > > >
> > > > > In suspend_device_irqs():
> > > > >
> > > > > (1) If all actions in the list have the same setting (eg. IRQF_NO_SUSPEND unset),
> > > > > keep the current behavior.
> > > > > (2) If the actions have different settings:
> > > > > - Actions with IRQF_NO_SUSPEND set are not modified.
> > > > > - Actions with IRQF_NO_SUSPEND unset are switched over to a stub handler.
> > > > > - IRQS_SUSPEND_MODE (new flag) is set for the IRQ.
> > > >
> > > > Can we please do that in setup_irq() and let the shared ones always
> > > > run through the stub? That keeps suspend/resume_device_irqs() simple.
> > >
> > > OK
> >
> > I've tried to do that, but encountered a problem. The stub handler is called
> > with irq, dev_id as arguments and for the "interrupts are not suspended" case
> > (common) it has to use irq to find the irq_desc and then it has to use dev_id
> > to find the irqaction to call the original handler from there. That seemed to
> > be a bit too much of a penalty to me. Especially for people who never suspend
> > their machines. :-)
> >
> > For this reason, I went for changing handlers in suspend_device_irqs() and
> > back in resume_device_irqs(). That's not terribly complicated (the restoration
> > in particular is pretty simple) and it should be easily reusable for the wakeup
> > interrupts case. resume_device_irqs() wouldn't need any more changes for that,
> > for example. It minimally affects systems that don't suspend too.
> >
> > I also ended up adding a new interrupt handler return code (IRQ_SUSPENDED).
> > I could add a new irq_desc flag instead, but then the new code in suspend_device_irqs()
> > and the new check in note_interrupt() would need to be slightly more complicated.
>
> Actually, if we have a global irqs_suspended state variable, it will be much
> simpler to handle wakeup interrupts going forward, because in that case we'll
> be able to keep their original interrupt handlers and IRQ_HANDLED from them
> will be interpreted as a wakeup event automatically.

I realized that with this, suspend_device_irqs() will be racy, because it
switches handlers and modifies irqs_suspended at different times then.
I'm not sure how much of a problem that would be, but it's better to
ensure that both the handler and note_interrupt() will be "switched" at
the same time, which means addin a wrapper handler at the __setup_irq()
time, after all.

To avoid the problem mentioned above, I'm using dev_id to store the action's
address and an additional "real dev_id" field to store the original value.
This version seems to work.

Rafael

---
drivers/base/power/main.c | 1
drivers/base/power/wakeup.c | 20 ++++++++++++++++
include/linux/interrupt.h | 4 +++
include/linux/irqdesc.h | 1
include/linux/suspend.h | 3 ++
kernel/irq/handle.c | 3 --
kernel/irq/internals.h | 3 ++
kernel/irq/manage.c | 53 ++++++++++++++++++++++++++++++++++++++++++--
kernel/irq/pm.c | 10 ++++----
kernel/irq/spurious.c | 13 ++++++++++
10 files changed, 103 insertions(+), 8 deletions(-)

Index: linux-pm/kernel/irq/manage.c
===================================================================
--- linux-pm.orig/kernel/irq/manage.c
+++ linux-pm/kernel/irq/manage.c
@@ -385,7 +385,7 @@ 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))
+ if (!desc->action || desc->skip_suspend)
return;
desc->istate |= IRQS_SUSPENDED;
}
@@ -658,6 +658,44 @@ int irq_set_parent(int irq, int parent_i
}
#endif

+bool irqs_suspended __read_mostly;
+
+void set_irqs_suspended(bool on)
+{
+ struct irq_desc *desc;
+ int irq;
+
+ irqs_suspended = on;
+ for_each_irq_desc(irq, desc)
+ synchronize_irq(irq);
+}
+
+/*
+ * Wrapper handler for shared interrupts.
+ */
+static irqreturn_t irq_shared_wrapper_handler(int irq, void *dev_id)
+{
+ struct irqaction *action;
+
+ if (unlikely(irqs_suspended))
+ return IRQ_NONE;
+
+ action = dev_id;
+ return action->s_handler(irq, action->s_dev_id);
+}
+
+static void irq_shared_wrap_handler(struct irqaction *action)
+{
+ if (action->handler == irq_shared_wrapper_handler ||
+ (action->flags & IRQF_NO_SUSPEND))
+ return;
+
+ action->s_handler = action->handler;
+ action->handler = irq_shared_wrapper_handler;
+ action->s_dev_id = action->dev_id;
+ action->dev_id = action;
+}
+
/*
* Default primary interrupt handler for threaded interrupts. Is
* assigned as primary handler when request_threaded_irq is called
@@ -1088,6 +1126,7 @@ __setup_irq(unsigned int irq, struct irq

/* add new interrupt at end of irq queue */
do {
+ irq_shared_wrap_handler(old);
/*
* Or all existing action->thread_mask bits,
* so we can find the next zero bit for this
@@ -1097,6 +1136,7 @@ __setup_irq(unsigned int irq, struct irq
old_ptr = &old->next;
old = *old_ptr;
} while (old);
+ irq_shared_wrap_handler(new);
shared = 1;
}

@@ -1222,6 +1262,9 @@ __setup_irq(unsigned int irq, struct irq
desc->irq_count = 0;
desc->irqs_unhandled = 0;

+ if (new->flags & IRQF_NO_SUSPEND)
+ desc->skip_suspend++;
+
/*
* Check whether we disabled the irq via the spurious handler
* before. Reenable it and give it another chance.
@@ -1328,13 +1371,19 @@ static struct irqaction *__free_irq(unsi
return NULL;
}

- if (action->dev_id == dev_id)
+ if (action->dev_id == dev_id || action->s_dev_id == dev_id)
break;
action_ptr = &action->next;
}

/* Found it - now remove it from the list of entries: */
*action_ptr = action->next;
+ if (action->flags & IRQF_NO_SUSPEND) {
+ desc->skip_suspend--;
+ } else if (action->handler == irq_shared_wrapper_handler) {
+ action->handler = action->s_handler;
+ action->dev_id = action->s_dev_id;
+ }

/* If this was the last handler, shut down the IRQ line: */
if (!desc->action) {
Index: linux-pm/include/linux/interrupt.h
===================================================================
--- linux-pm.orig/include/linux/interrupt.h
+++ linux-pm/include/linux/interrupt.h
@@ -90,8 +90,10 @@ typedef irqreturn_t (*irq_handler_t)(int
/**
* struct irqaction - per interrupt action descriptor
* @handler: interrupt handler function
+ * @s_handler: interrupt handler function for shared interrupts
* @name: name of the device
* @dev_id: cookie to identify the device
+ * @s_dev_id: cookie to identify the device for shared interrupts
* @percpu_dev_id: cookie to identify the device
* @next: pointer to the next irqaction for shared interrupts
* @irq: interrupt number
@@ -105,6 +107,8 @@ typedef irqreturn_t (*irq_handler_t)(int
struct irqaction {
irq_handler_t handler;
void *dev_id;
+ irq_handler_t s_handler;
+ void *s_dev_id;
void __percpu *percpu_dev_id;
struct irqaction *next;
irq_handler_t thread_fn;
Index: linux-pm/kernel/irq/handle.c
===================================================================
--- linux-pm.orig/kernel/irq/handle.c
+++ linux-pm/kernel/irq/handle.c
@@ -175,8 +175,7 @@ handle_irq_event_percpu(struct irq_desc

add_interrupt_randomness(irq, flags);

- if (!noirqdebug)
- note_interrupt(irq, desc, retval);
+ note_interrupt(irq, desc, retval);
return retval;
}

Index: linux-pm/kernel/irq/spurious.c
===================================================================
--- linux-pm.orig/kernel/irq/spurious.c
+++ linux-pm/kernel/irq/spurious.c
@@ -13,6 +13,7 @@
#include <linux/interrupt.h>
#include <linux/moduleparam.h>
#include <linux/timer.h>
+#include <linux/suspend.h>

#include "internals.h"

@@ -275,6 +276,18 @@ try_misrouted_irq(unsigned int irq, stru
void note_interrupt(unsigned int irq, struct irq_desc *desc,
irqreturn_t action_ret)
{
+ if (unlikely(irqs_suspended && action_ret == IRQ_NONE)) {
+ pr_err_ratelimited("IRQ %d: Unhandled while suspended\n", irq);
+ desc->istate |= IRQS_SUSPENDED;
+ desc->depth++;
+ irq_disable(desc);
+ pm_system_wakeup();
+ return;
+ }
+
+ if (noirqdebug)
+ return;
+
if (desc->istate & IRQS_POLL_INPROGRESS ||
irq_settings_is_polled(desc))
return;
Index: linux-pm/include/linux/suspend.h
===================================================================
--- linux-pm.orig/include/linux/suspend.h
+++ linux-pm/include/linux/suspend.h
@@ -371,6 +371,8 @@ extern int unregister_pm_notifier(struct
extern bool events_check_enabled;

extern bool pm_wakeup_pending(void);
+extern void pm_system_wakeup(void);
+extern void pm_wakeup_clear(void);
extern bool pm_get_wakeup_count(unsigned int *count, bool block);
extern bool pm_save_wakeup_count(unsigned int count);
extern void pm_wakep_autosleep_enabled(bool set);
@@ -418,6 +420,7 @@ static inline int unregister_pm_notifier
#define pm_notifier(fn, pri) do { (void)(fn); } while (0)

static inline bool pm_wakeup_pending(void) { return false; }
+static inline void pm_system_wakeup(void) {}

static inline void lock_system_sleep(void) {}
static inline void unlock_system_sleep(void) {}
Index: linux-pm/drivers/base/power/wakeup.c
===================================================================
--- linux-pm.orig/drivers/base/power/wakeup.c
+++ linux-pm/drivers/base/power/wakeup.c
@@ -691,6 +691,8 @@ void pm_print_active_wakeup_sources(void
}
EXPORT_SYMBOL_GPL(pm_print_active_wakeup_sources);

+static bool abort_suspend;
+
/**
* pm_wakeup_pending - Check if power transition in progress should be aborted.
*
@@ -712,6 +714,7 @@ bool pm_wakeup_pending(void)
ret = (cnt != saved_count || inpr > 0);
events_check_enabled = !ret;
}
+ ret = ret || abort_suspend;
spin_unlock_irqrestore(&events_lock, flags);

if (ret) {
@@ -722,6 +725,23 @@ bool pm_wakeup_pending(void)
return ret;
}

+void pm_system_wakeup(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&events_lock, flags);
+ abort_suspend = true;
+ spin_unlock_irqrestore(&events_lock, flags);
+ freeze_wake();
+}
+
+void pm_wakeup_clear(void)
+{
+ spin_lock_irq(&events_lock);
+ abort_suspend = false;
+ spin_unlock_irq(&events_lock);
+}
+
/**
* pm_get_wakeup_count - Read the number of registered wakeup events.
* @count: Address to store the value at.
Index: linux-pm/drivers/base/power/main.c
===================================================================
--- linux-pm.orig/drivers/base/power/main.c
+++ linux-pm/drivers/base/power/main.c
@@ -1648,6 +1648,7 @@ int dpm_suspend_start(pm_message_t state
{
int error;

+ pm_wakeup_clear();
error = dpm_prepare(state);
if (error) {
suspend_stats.failed_prepare++;
Index: linux-pm/kernel/irq/pm.c
===================================================================
--- linux-pm.orig/kernel/irq/pm.c
+++ linux-pm/kernel/irq/pm.c
@@ -10,6 +10,7 @@
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/syscore_ops.h>
+#include <linux/suspend.h>

#include "internals.h"

@@ -33,10 +34,7 @@ void suspend_device_irqs(void)
__disable_irq(desc, irq, true);
raw_spin_unlock_irqrestore(&desc->lock, flags);
}
-
- for_each_irq_desc(irq, desc)
- if (desc->istate & IRQS_SUSPENDED)
- synchronize_irq(irq);
+ set_irqs_suspended(true);
}
EXPORT_SYMBOL_GPL(suspend_device_irqs);

@@ -90,6 +88,7 @@ device_initcall(irq_pm_init_ops);
*/
void resume_device_irqs(void)
{
+ set_irqs_suspended(false);
resume_irqs(false);
}
EXPORT_SYMBOL_GPL(resume_device_irqs);
@@ -102,6 +101,9 @@ int check_wakeup_irqs(void)
struct irq_desc *desc;
int irq;

+ if (pm_wakeup_pending())
+ return -EBUSY;
+
for_each_irq_desc(irq, desc) {
/*
* Only interrupts which are marked as wakeup source
Index: linux-pm/kernel/irq/internals.h
===================================================================
--- linux-pm.orig/kernel/irq/internals.h
+++ linux-pm/kernel/irq/internals.h
@@ -17,6 +17,9 @@
#define istate core_internal_state__do_not_mess_with_it

extern bool noirqdebug;
+extern bool irqs_suspended;
+
+extern void set_irqs_suspended(bool on);

/*
* Bits used by threaded handlers:
Index: linux-pm/include/linux/irqdesc.h
===================================================================
--- linux-pm.orig/include/linux/irqdesc.h
+++ linux-pm/include/linux/irqdesc.h
@@ -51,6 +51,7 @@ struct irq_desc {
unsigned int core_internal_state__do_not_mess_with_it;
unsigned int depth; /* nested irq disables */
unsigned int wake_depth; /* nested wake enables */
+ unsigned int skip_suspend;
unsigned int irq_count; /* For detecting broken IRQs */
unsigned long last_unhandled; /* Aging timer for unhandled count */
unsigned int irqs_unhandled;