genirq: Add IRQF_NO_AUTOEN for request_irq/nmi()

Many drivers don't want interrupts enabled automatically via request_irq().
So they are handling this issue by either way of the below two:

(1)
  irq_set_status_flags(irq, IRQ_NOAUTOEN);
  request_irq(dev, irq...);

(2)
  request_irq(dev, irq...);
  disable_irq(irq);

The code in the second way is silly and unsafe. In the small time gap
between request_irq() and disable_irq(), interrupts can still come.

The code in the first way is safe though it's subobtimal.

Add a new IRQF_NO_AUTOEN flag which can be handed in by drivers to
request_irq() and request_nmi(). It prevents the automatic enabling of the
requested interrupt/nmi in the same safe way as #1 above. With that the
various usage sites of #1 and #2 above can be simplified and corrected.

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: dmitry.torokhov@gmail.com
Link: https://lore.kernel.org/r/20210302224916.13980-2-song.bao.hua@hisilicon.com

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 967e257..76f1161 100644 (file)
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -61,6 +61,9 @@
  *                interrupt handler after suspending interrupts. For system
  *                wakeup devices users need to implement wakeup detection in
  *                their interrupt handlers.
+ * IRQF_NO_AUTOEN - Don't enable IRQ or NMI automatically when users request it.
+ *                Users will enable it explicitly by enable_irq() or enable_nmi()
+ *                later.
  */
 #define IRQF_SHARED            0x00000080
 #define IRQF_PROBE_SHARED      0x00000100
@@ -74,6 +77,7 @@
 #define IRQF_NO_THREAD         0x00010000
 #define IRQF_EARLY_RESUME      0x00020000
 #define IRQF_COND_SUSPEND      0x00040000
+#define IRQF_NO_AUTOEN         0x00080000
 
 #define IRQF_TIMER             (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
 

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index dec3f73..97c231a 100644 (file)
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1693,7 +1693,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
                        irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
                }
 
-               if (irq_settings_can_autoenable(desc)) {
+               if (!(new->flags & IRQF_NO_AUTOEN) &&
+                   irq_settings_can_autoenable(desc)) {
                        irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
                } else {
                        /*
@@ -2086,10 +2087,15 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
         * which interrupt is which (messes up the interrupt freeing
         * logic etc).
         *
+        * Also shared interrupts do not go well with disabling auto enable.
+        * The sharing interrupt might request it while it's still disabled
+        * and then wait for interrupts forever.
+        *
         * Also IRQF_COND_SUSPEND only makes sense for shared interrupts and
         * it cannot be set along with IRQF_NO_SUSPEND.
         */
        if (((irqflags & IRQF_SHARED) && !dev_id) ||
+           ((irqflags & IRQF_SHARED) && (irqflags & IRQF_NO_AUTOEN)) ||
            (!(irqflags & IRQF_SHARED) && (irqflags & IRQF_COND_SUSPEND)) ||
            ((irqflags & IRQF_NO_SUSPEND) && (irqflags & IRQF_COND_SUSPEND)))
                return -EINVAL;
@@ -2245,7 +2251,8 @@ int request_nmi(unsigned int irq, irq_handler_t handler,
 
        desc = irq_to_desc(irq);
 
-       if (!desc || irq_settings_can_autoenable(desc) ||
+       if (!desc || (irq_settings_can_autoenable(desc) &&
+           !(irqflags & IRQF_NO_AUTOEN)) ||
            !irq_settings_can_request(desc) ||
            WARN_ON(irq_settings_is_per_cpu_devid(desc)) ||
            !irq_supports_nmi(desc))