[PATCH] powerpc/powernv: process all OPAL event interrupts with kopald
Nicholas Piggin
npiggin at gmail.com
Fri May 11 03:20:05 AEST 2018
Using irq_work for processing OPAL event interrupts is not necessary.
irq_work is typically used to schedule work from NMI context, a
softirq may be more appropriate. However OPAL events are not
particularly performance or latency critical, so they can all be
invoked by kopald.
This patch removes the irq_work queueing, and instead wakes up
kopald when there is an event to be processed. kopald processes
interrupts individually, enabling irqs and calling cond_resched
between each one to minimise latencies.
Event handlers themselves should still use threaded handlers,
workqueues, etc. as necessary to avoid high interrupts-off latencies
within any single interrupt.
Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
---
arch/powerpc/platforms/powernv/opal-irqchip.c | 87 +++++++++----------
arch/powerpc/platforms/powernv/opal.c | 23 +++--
arch/powerpc/platforms/powernv/powernv.h | 3 +-
3 files changed, 52 insertions(+), 61 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/opal-irqchip.c b/arch/powerpc/platforms/powernv/opal-irqchip.c
index 9d1b8c0aaf93..354fa53947be 100644
--- a/arch/powerpc/platforms/powernv/opal-irqchip.c
+++ b/arch/powerpc/platforms/powernv/opal-irqchip.c
@@ -22,7 +22,6 @@
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/slab.h>
-#include <linux/irq_work.h>
#include <asm/machdep.h>
#include <asm/opal.h>
@@ -38,37 +37,47 @@ struct opal_event_irqchip {
unsigned long mask;
};
static struct opal_event_irqchip opal_event_irqchip;
-
+static u64 last_outstanding_events;
static unsigned int opal_irq_count;
static unsigned int *opal_irqs;
-static void opal_handle_irq_work(struct irq_work *work);
-static u64 last_outstanding_events;
-static struct irq_work opal_event_irq_work = {
- .func = opal_handle_irq_work,
-};
-
-void opal_handle_events(uint64_t events)
+void opal_handle_events(void)
{
- int virq, hwirq = 0;
- u64 mask = opal_event_irqchip.mask;
+ __be64 events = 0;
+ u64 e;
+
+ e = READ_ONCE(last_outstanding_events) & opal_event_irqchip.mask;
+again:
+ while (e) {
+ int virq, hwirq;
+
+ hwirq = fls64(e) - 1;
+ e &= ~BIT_ULL(hwirq);
+
+ local_irq_disable();
+ virq = irq_find_mapping(opal_event_irqchip.domain, hwirq);
+ if (virq) {
+ irq_enter();
+ generic_handle_irq(virq);
+ irq_exit();
+ }
+ local_irq_enable();
- if (!in_irq() && (events & mask)) {
- last_outstanding_events = events;
- irq_work_queue(&opal_event_irq_work);
- return;
+ cond_resched();
}
+ last_outstanding_events = 0;
+ if (opal_poll_events(&events) != OPAL_SUCCESS)
+ return;
+ e = be64_to_cpu(events) & opal_event_irqchip.mask;
+ if (e)
+ goto again;
+}
- while (events & mask) {
- hwirq = fls64(events) - 1;
- if (BIT_ULL(hwirq) & mask) {
- virq = irq_find_mapping(opal_event_irqchip.domain,
- hwirq);
- if (virq)
- generic_handle_irq(virq);
- }
- events &= ~BIT_ULL(hwirq);
- }
+bool opal_have_pending_events(void)
+{
+ if (last_outstanding_events & opal_event_irqchip.mask)
+ return true;
+ return false;
}
static void opal_event_mask(struct irq_data *d)
@@ -78,24 +87,9 @@ static void opal_event_mask(struct irq_data *d)
static void opal_event_unmask(struct irq_data *d)
{
- __be64 events;
-
set_bit(d->hwirq, &opal_event_irqchip.mask);
-
- opal_poll_events(&events);
- last_outstanding_events = be64_to_cpu(events);
-
- /*
- * We can't just handle the events now with opal_handle_events().
- * If we did we would deadlock when opal_event_unmask() is called from
- * handle_level_irq() with the irq descriptor lock held, because
- * calling opal_handle_events() would call generic_handle_irq() and
- * then handle_level_irq() which would try to take the descriptor lock
- * again. Instead queue the events for later.
- */
- if (last_outstanding_events & opal_event_irqchip.mask)
- /* Need to retrigger the interrupt */
- irq_work_queue(&opal_event_irq_work);
+ if (opal_have_pending_events())
+ opal_wake_poller();
}
static int opal_event_set_type(struct irq_data *d, unsigned int flow_type)
@@ -136,16 +130,13 @@ static irqreturn_t opal_interrupt(int irq, void *data)
__be64 events;
opal_handle_interrupt(virq_to_hw(irq), &events);
- opal_handle_events(be64_to_cpu(events));
+ last_outstanding_events = be64_to_cpu(events);
+ if (opal_have_pending_events())
+ opal_wake_poller();
return IRQ_HANDLED;
}
-static void opal_handle_irq_work(struct irq_work *work)
-{
- opal_handle_events(last_outstanding_events);
-}
-
static int opal_event_match(struct irq_domain *h, struct device_node *node,
enum irq_domain_bus_token bus_token)
{
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index 48fbb41af5d1..0d539c661748 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -540,21 +540,15 @@ int opal_hmi_exception_early(struct pt_regs *regs)
/* HMI exception handler called in virtual mode during check_irq_replay. */
int opal_handle_hmi_exception(struct pt_regs *regs)
{
- s64 rc;
- __be64 evt = 0;
-
/*
* Check if HMI event is available.
- * if Yes, then call opal_poll_events to pull opal messages and
- * process them.
+ * if Yes, then wake kopald to process them.
*/
if (!local_paca->hmi_event_available)
return 0;
local_paca->hmi_event_available = 0;
- rc = opal_poll_events(&evt);
- if (rc == OPAL_SUCCESS && evt)
- opal_handle_events(be64_to_cpu(evt));
+ opal_wake_poller();
return 1;
}
@@ -757,14 +751,19 @@ static void __init opal_imc_init_dev(void)
static int kopald(void *unused)
{
unsigned long timeout = msecs_to_jiffies(opal_heartbeat) + 1;
- __be64 events;
set_freezable();
do {
try_to_freeze();
- opal_poll_events(&events);
- opal_handle_events(be64_to_cpu(events));
- schedule_timeout_interruptible(timeout);
+
+ opal_handle_events();
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (opal_have_pending_events())
+ __set_current_state(TASK_RUNNING);
+ else
+ schedule_timeout(timeout);
+
} while (!kthread_should_stop());
return 0;
diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
index 94f17ab1374b..fd4a1c5a6369 100644
--- a/arch/powerpc/platforms/powernv/powernv.h
+++ b/arch/powerpc/platforms/powernv/powernv.h
@@ -24,7 +24,8 @@ extern u32 pnv_get_supported_cpuidle_states(void);
extern void pnv_lpc_init(void);
-extern void opal_handle_events(uint64_t events);
+extern void opal_handle_events(void);
+extern bool opal_have_pending_events(void);
extern void opal_event_shutdown(void);
bool cpu_core_split_required(void);
--
2.17.0
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