From dc9b229a58dc0dfed34272ff26c6d5fd17c674e0 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 13 Jul 2012 19:29:45 +0200
Subject: [PATCH] genirq: Allow irq chips to mark themself oneshot safe
Some interrupt chips like MSI are oneshot safe by implementation. For
those interrupts we can avoid the mask/unmask sequence for threaded
interrupt handlers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1207132056540.32033@ionos
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Jan Kiszka <jan.kiszka@web.de>
---
include/linux/irq.h | 1 +
kernel/irq/manage.c | 15 ++++++++++++++-
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 553fb66da130..216b0ba109d7 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -349,6 +349,7 @@ enum {
IRQCHIP_MASK_ON_SUSPEND = (1 << 2),
IRQCHIP_ONOFFLINE_ENABLED = (1 << 3),
IRQCHIP_SKIP_SET_WAKE = (1 << 4),
+ IRQCHIP_ONESHOT_SAFE = (1 << 5),
};
/* This include will go away once we isolated irq_desc usage to core code */
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 8c548232ba39..2e326d1ebec1 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -959,6 +959,18 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
goto out_thread;
}
+ /*
+ * Drivers are often written to work w/o knowledge about the
+ * underlying irq chip implementation, so a request for a
+ * threaded irq without a primary hard irq context handler
+ * requires the ONESHOT flag to be set. Some irq chips like
+ * MSI based interrupts are per se one shot safe. Check the
+ * chip flags, so we can avoid the unmask dance at the end of
+ * the threaded handler for those.
+ */
+ if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
+ new->flags &= ~IRQF_ONESHOT;
+
/*
* The following block of code has to be executed atomically
*/
@@ -1033,7 +1045,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
*/
new->thread_mask = 1 << ffz(thread_mask);
- } else if (new->handler == irq_default_primary_handler) {
+ } else if (new->handler == irq_default_primary_handler &&
+ !(desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)) {
/*
* The interrupt was requested with handler = NULL, so
* we use the default primary handler for it. But it