139 lines
4.8 KiB
Diff
139 lines
4.8 KiB
Diff
Subject: genirq: Allow disabling of softirq processing in irq thread context
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Tue, 31 Jan 2012 13:01:27 +0100
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.1-rt3.tar.xz
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The processing of softirqs in irq thread context is a performance gain
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for the non-rt workloads of a system, but it's counterproductive for
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interrupts which are explicitely related to the realtime
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workload. Allow such interrupts to prevent softirq processing in their
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thread context.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/interrupt.h | 2 ++
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include/linux/irq.h | 4 +++-
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kernel/irq/manage.c | 15 +++++++++++++++
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kernel/irq/settings.h | 12 ++++++++++++
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4 files changed, 32 insertions(+), 1 deletion(-)
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diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
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index eeceac3376fc..4a60c2618a6e 100644
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--- a/include/linux/interrupt.h
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+++ b/include/linux/interrupt.h
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@@ -61,6 +61,7 @@
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* interrupt handler after suspending interrupts. For system
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* wakeup devices users need to implement wakeup detection in
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* their interrupt handlers.
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+ * IRQF_NO_SOFTIRQ_CALL - Do not process softirqs in the irq thread context (RT)
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*/
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#define IRQF_SHARED 0x00000080
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#define IRQF_PROBE_SHARED 0x00000100
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@@ -74,6 +75,7 @@
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#define IRQF_NO_THREAD 0x00010000
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#define IRQF_EARLY_RESUME 0x00020000
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#define IRQF_COND_SUSPEND 0x00040000
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+#define IRQF_NO_SOFTIRQ_CALL 0x00080000
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#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
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diff --git a/include/linux/irq.h b/include/linux/irq.h
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index 201de12a9957..c8fa3f632cec 100644
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--- a/include/linux/irq.h
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+++ b/include/linux/irq.h
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@@ -69,6 +69,7 @@ enum irqchip_irq_state;
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* IRQ_IS_POLLED - Always polled by another interrupt. Exclude
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* it from the spurious interrupt detection
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* mechanism and from core side polling.
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+ * IRQ_NO_SOFTIRQ_CALL - No softirq processing in the irq thread context (RT)
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* IRQ_DISABLE_UNLAZY - Disable lazy irq disable
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*/
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enum {
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@@ -96,13 +97,14 @@ enum {
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IRQ_PER_CPU_DEVID = (1 << 17),
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IRQ_IS_POLLED = (1 << 18),
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IRQ_DISABLE_UNLAZY = (1 << 19),
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+ IRQ_NO_SOFTIRQ_CALL = (1 << 20),
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};
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#define IRQF_MODIFY_MASK \
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(IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
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IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
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IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID | \
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- IRQ_IS_POLLED | IRQ_DISABLE_UNLAZY)
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+ IRQ_IS_POLLED | IRQ_DISABLE_UNLAZY | IRQ_NO_SOFTIRQ_CALL)
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#define IRQ_NO_BALANCING_MASK (IRQ_PER_CPU | IRQ_NO_BALANCING)
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diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
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index 9dbdccab3b6a..748e7cd2b053 100644
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--- a/kernel/irq/manage.c
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+++ b/kernel/irq/manage.c
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@@ -932,6 +932,18 @@ irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
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irq_finalize_oneshot(desc, action);
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local_bh_enable();
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+ /*
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+ * Interrupts which have real time requirements can be set up
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+ * to avoid softirq processing in the thread handler. This is
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+ * safe as these interrupts do not raise soft interrupts.
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+ */
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+ if (irq_settings_no_softirq_call(desc)) {
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+ if (WARN_ON(current->softirq_nestcnt == 0))
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+ return ret;
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+ if (--current->softirq_nestcnt == 0)
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+ migrate_enable();
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+ } else
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+ local_bh_enable();
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return ret;
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}
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@@ -1441,6 +1453,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
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irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
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}
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+ if (new->flags & IRQF_NO_SOFTIRQ_CALL)
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+ irq_settings_set_no_softirq_call(desc);
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+
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if (irq_settings_can_autoenable(desc)) {
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irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
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} else {
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diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
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index e43795cd2ccf..47e2f9e23586 100644
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--- a/kernel/irq/settings.h
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+++ b/kernel/irq/settings.h
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@@ -17,6 +17,7 @@ enum {
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_IRQ_PER_CPU_DEVID = IRQ_PER_CPU_DEVID,
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_IRQ_IS_POLLED = IRQ_IS_POLLED,
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_IRQ_DISABLE_UNLAZY = IRQ_DISABLE_UNLAZY,
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+ _IRQ_NO_SOFTIRQ_CALL = IRQ_NO_SOFTIRQ_CALL,
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_IRQF_MODIFY_MASK = IRQF_MODIFY_MASK,
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};
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@@ -31,6 +32,7 @@ enum {
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#define IRQ_PER_CPU_DEVID GOT_YOU_MORON
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#define IRQ_IS_POLLED GOT_YOU_MORON
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#define IRQ_DISABLE_UNLAZY GOT_YOU_MORON
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+#define IRQ_NO_SOFTIRQ_CALL GOT_YOU_MORON
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#undef IRQF_MODIFY_MASK
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#define IRQF_MODIFY_MASK GOT_YOU_MORON
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@@ -41,6 +43,16 @@ irq_settings_clr_and_set(struct irq_desc *desc, u32 clr, u32 set)
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desc->status_use_accessors |= (set & _IRQF_MODIFY_MASK);
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}
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+static inline bool irq_settings_no_softirq_call(struct irq_desc *desc)
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+{
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+ return desc->status_use_accessors & _IRQ_NO_SOFTIRQ_CALL;
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+}
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+
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+static inline void irq_settings_set_no_softirq_call(struct irq_desc *desc)
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+{
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+ desc->status_use_accessors |= _IRQ_NO_SOFTIRQ_CALL;
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+}
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+
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static inline bool irq_settings_is_per_cpu(struct irq_desc *desc)
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{
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return desc->status_use_accessors & _IRQ_PER_CPU;
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