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>

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 553fb66da130a3a9b3700958c5cce22a6b5cda73..216b0ba109d72f453836568e1aa6c7b7c85e21a6 100644 (file)
--- 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 8c548232ba39daf0f7320d64f19d85775000201a..2e326d1ebec17a095653b33a3d272515e86c2e39 100644 (file)
--- 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