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From 5661e9b00a3bd5346bf2105a9061b63a994820d3 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 31 Jan 2012 13:01:27 +0100
Subject: [PATCH 168/274] genirq: Allow disabling of softirq processing in irq
thread context
The processing of softirqs in irq thread context is a performance gain
for the non-rt workloads of a system, but it's counterproductive for
interrupts which are explicitely related to the realtime
workload. Allow such interrupts to prevent softirq processing in their
thread context.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable-rt@vger.kernel.org
---
include/linux/interrupt.h | 2 ++
include/linux/irq.h | 5 ++++-
kernel/irq/manage.c | 13 ++++++++++++-
kernel/irq/settings.h | 12 ++++++++++++
kernel/softirq.c | 7 +++++++
5 files changed, 37 insertions(+), 2 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index be33625..773dbc9 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -59,6 +59,7 @@
* IRQF_NO_THREAD - Interrupt cannot be threaded
* IRQF_EARLY_RESUME - Resume IRQ early during syscore instead of at device
* resume time.
+ * IRQF_NO_SOFTIRQ_CALL - Do not process softirqs in the irq thread context (RT)
*/
#define IRQF_DISABLED 0x00000020
#define IRQF_SAMPLE_RANDOM 0x00000040
@@ -73,6 +74,7 @@
#define IRQF_FORCE_RESUME 0x00008000
#define IRQF_NO_THREAD 0x00010000
#define IRQF_EARLY_RESUME 0x00020000
+#define IRQF_NO_SOFTIRQ_CALL 0x00040000
#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
diff --git a/include/linux/irq.h b/include/linux/irq.h
index b27cfcf..496fa99 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -73,6 +73,7 @@ typedef void (*irq_preflow_handler_t)(struct irq_data *data);
* IRQ_MOVE_PCNTXT - Interrupt can be migrated from process context
* IRQ_NESTED_TRHEAD - Interrupt nests into another thread
* IRQ_PER_CPU_DEVID - Dev_id is a per-cpu variable
+ * IRQ_NO_SOFTIRQ_CALL - No softirq processing in the irq thread context (RT)
*/
enum {
IRQ_TYPE_NONE = 0x00000000,
@@ -97,12 +98,14 @@ enum {
IRQ_NESTED_THREAD = (1 << 15),
IRQ_NOTHREAD = (1 << 16),
IRQ_PER_CPU_DEVID = (1 << 17),
+ IRQ_NO_SOFTIRQ_CALL = (1 << 18),
};
#define IRQF_MODIFY_MASK \
(IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
- IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID)
+ IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID | \
+ IRQ_NO_SOFTIRQ_CALL)
#define IRQ_NO_BALANCING_MASK (IRQ_PER_CPU | IRQ_NO_BALANCING)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index ab8f58c..ede56ac 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -749,7 +749,15 @@ irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
local_bh_disable();
ret = action->thread_fn(action->irq, action->dev_id);
irq_finalize_oneshot(desc, action);
- local_bh_enable();
+ /*
+ * Interrupts which have real time requirements can be set up
+ * to avoid softirq processing in the thread handler. This is
+ * safe as these interrupts do not raise soft interrupts.
+ */
+ if (irq_settings_no_softirq_call(desc))
+ _local_bh_enable();
+ else
+ local_bh_enable();
return ret;
}
@@ -1055,6 +1063,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
}
+ if (new->flags & IRQF_NO_SOFTIRQ_CALL)
+ irq_settings_set_no_softirq_call(desc);
+
/* Set default affinity mask once everything is setup */
setup_affinity(irq, desc, mask);
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 1162f10..0d2c381 100644
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -14,6 +14,7 @@ enum {
_IRQ_NO_BALANCING = IRQ_NO_BALANCING,
_IRQ_NESTED_THREAD = IRQ_NESTED_THREAD,
_IRQ_PER_CPU_DEVID = IRQ_PER_CPU_DEVID,
+ _IRQ_NO_SOFTIRQ_CALL = IRQ_NO_SOFTIRQ_CALL,
_IRQF_MODIFY_MASK = IRQF_MODIFY_MASK,
};
@@ -26,6 +27,7 @@ enum {
#define IRQ_NOAUTOEN GOT_YOU_MORON
#define IRQ_NESTED_THREAD GOT_YOU_MORON
#define IRQ_PER_CPU_DEVID GOT_YOU_MORON
+#define IRQ_NO_SOFTIRQ_CALL GOT_YOU_MORON
#undef IRQF_MODIFY_MASK
#define IRQF_MODIFY_MASK GOT_YOU_MORON
@@ -36,6 +38,16 @@ irq_settings_clr_and_set(struct irq_desc *desc, u32 clr, u32 set)
desc->status_use_accessors |= (set & _IRQF_MODIFY_MASK);
}
+static inline bool irq_settings_no_softirq_call(struct irq_desc *desc)
+{
+ return desc->status_use_accessors & _IRQ_NO_SOFTIRQ_CALL;
+}
+
+static inline void irq_settings_set_no_softirq_call(struct irq_desc *desc)
+{
+ desc->status_use_accessors |= _IRQ_NO_SOFTIRQ_CALL;
+}
+
static inline bool irq_settings_is_per_cpu(struct irq_desc *desc)
{
return desc->status_use_accessors & _IRQ_PER_CPU;
diff --git a/kernel/softirq.c b/kernel/softirq.c
index aec7d69..35fb713 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -425,6 +425,13 @@ void local_bh_enable_ip(unsigned long ip)
}
EXPORT_SYMBOL(local_bh_enable_ip);
+void _local_bh_enable(void)
+{
+ current->softirq_nestcnt--;
+ migrate_enable();
+}
+EXPORT_SYMBOL(_local_bh_enable);
+
/* For tracing */
int notrace __in_softirq(void)
{
--
1.7.10.4
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