genirq: enable polling for disabled screaming irqs

When we disable a screaming irq we never see it again.  If the irq
line is shared or if the driver half works this is a real pain.  So
periodically poll the handlers for screaming interrupts.

I use a timer instead of the classic irq poll technique of working off
the timer interrupt because when we use the local apic timers
note_interrupt is never called (bug?).  Further on a system with
dynamic ticks the timer interrupt might not even fire unless there is
a timer telling it it needs to.

I forced this case on my test system with an e1000 nic and my ssh
session remained responsive despite the interrupt handler only being
called every 10th of a second.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 91 insertions, 55 deletions

diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
index c66d3f10e853..19fe9d6ebfe8 100644
--- a/kernel/irq/spurious.c
+++ b/kernel/irq/spurious.c
@@ -12,83 +12,117 @@
 #include <linux/kallsyms.h>
 #include <linux/interrupt.h>
 #include <linux/moduleparam.h>
+#include <linux/timer.h>
 
 static int irqfixup __read_mostly;
 
+#define POLL_SPURIOUS_IRQ_INTERVAL (HZ/10)
+static void poll_spurious_irqs(unsigned long dummy);
+static DEFINE_TIMER(poll_spurious_irq_timer, poll_spurious_irqs, 0, 0);
+
 /*
  * Recovery handler for misrouted interrupts.
  */
-static int misrouted_irq(int irq)
+static int try_one_irq(int irq, struct irq_desc *desc)
 {
-        int i;
+        struct irqaction *action;
         int ok = 0;
         int work = 0;   /* Did we do work for a real IRQ */
 
-        for (i = 1; i < NR_IRQS; i++) {
-                struct irq_desc *desc = irq_desc + i;
-                struct irqaction *action;
-
-                if (i == irq)   /* Already tried */
-                        continue;
-
-                spin_lock(&desc->lock);
-                /* Already running on another processor */
-                if (desc->status & IRQ_INPROGRESS) {
-                        /*
-                         * Already running: If it is shared get the other
-                         * CPU to go looking for our mystery interrupt too
-                         */
-                        if (desc->action && (desc->action->flags & IRQF_SHARED))
-                                desc->status |= IRQ_PENDING;
-                        spin_unlock(&desc->lock);
-                        continue;
-                }
-                /* Honour the normal IRQ locking */
-                desc->status |= IRQ_INPROGRESS;
-                action = desc->action;
+        spin_lock(&desc->lock);
+        /* Already running on another processor */
+        if (desc->status & IRQ_INPROGRESS) {
+                /*
+                 * Already running: If it is shared get the other
+                 * CPU to go looking for our mystery interrupt too
+                 */
+                if (desc->action && (desc->action->flags & IRQF_SHARED))
+                        desc->status |= IRQ_PENDING;
                 spin_unlock(&desc->lock);
+                return ok;
+        }
+        /* Honour the normal IRQ locking */
+        desc->status |= IRQ_INPROGRESS;
+        action = desc->action;
+        spin_unlock(&desc->lock);
 
-                while (action) {
-                        /* Only shared IRQ handlers are safe to call */
-                        if (action->flags & IRQF_SHARED) {
-                                if (action->handler(i, action->dev_id) ==
-                                                IRQ_HANDLED)
-                                        ok = 1;
-                        }
-                        action = action->next;
+        while (action) {
+                /* Only shared IRQ handlers are safe to call */
+                if (action->flags & IRQF_SHARED) {
+                        if (action->handler(irq, action->dev_id) ==
+                                IRQ_HANDLED)
+                                ok = 1;
                 }
-                local_irq_disable();
-                /* Now clean up the flags */
-                spin_lock(&desc->lock);
-                action = desc->action;
+                action = action->next;
+        }
+        local_irq_disable();
+        /* Now clean up the flags */
+        spin_lock(&desc->lock);
+        action = desc->action;
 
+        /*
+         * While we were looking for a fixup someone queued a real
+         * IRQ clashing with our walk:
+         */
+        while ((desc->status & IRQ_PENDING) && action) {
                 /*
-                 * While we were looking for a fixup someone queued a real
-                 * IRQ clashing with our walk:
-                 */
-                while ((desc->status & IRQ_PENDING) && action) {
-                        /*
-                         * Perform real IRQ processing for the IRQ we deferred
-                         */
-                        work = 1;
-                        spin_unlock(&desc->lock);
-                        handle_IRQ_event(i, action);
-                        spin_lock(&desc->lock);
-                        desc->status &= ~IRQ_PENDING;
-                }
-                desc->status &= ~IRQ_INPROGRESS;
-                /*
-                 * If we did actual work for the real IRQ line we must let the
-                 * IRQ controller clean up too
+                 * Perform real IRQ processing for the IRQ we deferred
                  */
-                if (work && desc->chip && desc->chip->end)
-                        desc->chip->end(i);
+                work = 1;
                 spin_unlock(&desc->lock);
+                handle_IRQ_event(irq, action);
+                spin_lock(&desc->lock);
+                desc->status &= ~IRQ_PENDING;
+        }
+        desc->status &= ~IRQ_INPROGRESS;
+        /*
+         * If we did actual work for the real IRQ line we must let the
+         * IRQ controller clean up too
+         */
+        if (work && desc->chip && desc->chip->end)
+                desc->chip->end(irq);
+        spin_unlock(&desc->lock);
+
+        return ok;
+}
+
+static int misrouted_irq(int irq)
+{
+        int i;
+        int ok = 0;
+
+        for (i = 1; i < NR_IRQS; i++) {
+                struct irq_desc *desc = irq_desc + i;
+
+                if (i == irq)   /* Already tried */
+                        continue;
+
+                if (try_one_irq(i, desc))
+                        ok = 1;
         }
         /* So the caller can adjust the irq error counts */
         return ok;
 }
 
+static void poll_spurious_irqs(unsigned long dummy)
+{
+        int i;
+        for (i = 1; i < NR_IRQS; i++) {
+                struct irq_desc *desc = irq_desc + i;
+                unsigned int status;
+
+                /* Racy but it doesn't matter */
+                status = desc->status;
+                barrier();
+                if (!(status & IRQ_SPURIOUS_DISABLED))
+                        continue;
+
+                try_one_irq(i, desc);
+        }
+
+        mod_timer(&poll_spurious_irq_timer, jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
+}
+
 /*
  * If 99,900 of the previous 100,000 interrupts have not been handled
  * then assume that the IRQ is stuck in some manner. Drop a diagnostic
@@ -212,6 +246,8 @@ void note_interrupt(unsigned int irq, struct irq_desc *desc,
                 desc->status |= IRQ_DISABLED | IRQ_SPURIOUS_DISABLED;
                 desc->depth++;
                 desc->chip->disable(irq);
+
+                mod_timer(&poll_spurious_irq_timer, jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
         }
         desc->irqs_unhandled = 0;
 }