6 files changed, 93 insertions, 6 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 89835a4766a6..cac6cf9a588c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2436,6 +2436,10 @@ and is between 256 and 4096 characters. It is defined in the file
                         <deci-seconds>: poll all this frequency
                         0: no polling (default)
 
+        threadirqs      [KNL]
+                        Force threading of all interrupt handlers except those
+                        marked explicitely IRQF_NO_THREAD.
+
         topology=       [S390]
                         Format: {off | on}
                         Specify if the kernel should make use of the cpu
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 0fc3eb9397b4..f8a8af108e0c 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -383,6 +383,13 @@ static inline int disable_irq_wake(unsigned int irq)
 }
 #endif /* CONFIG_GENERIC_HARDIRQS */
 
+
+#ifdef CONFIG_IRQ_FORCED_THREADING
+extern bool force_irqthreads;
+#else
+#define force_irqthreads        (0)
+#endif
+
 #ifndef __ARCH_SET_SOFTIRQ_PENDING
 #define set_softirq_pending(x) (local_softirq_pending() = (x))
 #define or_softirq_pending(x)  (local_softirq_pending() |= (x))
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index 355b8c7957f5..144db9dcfcde 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -38,6 +38,9 @@ config HARDIRQS_SW_RESEND
 config IRQ_PREFLOW_FASTEOI
        bool
 
+config IRQ_FORCED_THREADING
+       bool
+
 config SPARSE_IRQ
         bool "Support sparse irq numbering"
         depends on HAVE_SPARSE_IRQ
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 935bec4bfa87..6c6ec9a49027 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -27,12 +27,14 @@ extern int noirqdebug;
  * IRQTF_DIED      - handler thread died
  * IRQTF_WARNED    - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed
  * IRQTF_AFFINITY  - irq thread is requested to adjust affinity
+ * IRQTF_FORCED_THREAD  - irq action is force threaded
  */
 enum {
         IRQTF_RUNTHREAD,
         IRQTF_DIED,
         IRQTF_WARNED,
         IRQTF_AFFINITY,
+        IRQTF_FORCED_THREAD,
 };
 
 /*
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 58c861367300..acd599a43bfb 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -17,6 +17,17 @@
 
 #include "internals.h"
 
+#ifdef CONFIG_IRQ_FORCED_THREADING
+__read_mostly bool force_irqthreads;
+
+static int __init setup_forced_irqthreads(char *arg)
+{
+        force_irqthreads = true;
+        return 0;
+}
+early_param("threadirqs", setup_forced_irqthreads);
+#endif
+
 /**
  *      synchronize_irq - wait for pending IRQ handlers (on other CPUs)
  *      @irq: interrupt number to wait for
@@ -702,6 +713,32 @@ irq_thread_check_affinity(struct irq_desc *desc, struct irqaction *action) { }
 #endif
 
 /*
+ * Interrupts which are not explicitely requested as threaded
+ * interrupts rely on the implicit bh/preempt disable of the hard irq
+ * context. So we need to disable bh here to avoid deadlocks and other
+ * side effects.
+ */
+static void
+irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
+{
+        local_bh_disable();
+        action->thread_fn(action->irq, action->dev_id);
+        irq_finalize_oneshot(desc, action, false);
+        local_bh_enable();
+}
+
+/*
+ * Interrupts explicitely requested as threaded interupts want to be
+ * preemtible - many of them need to sleep and wait for slow busses to
+ * complete.
+ */
+static void irq_thread_fn(struct irq_desc *desc, struct irqaction *action)
+{
+        action->thread_fn(action->irq, action->dev_id);
+        irq_finalize_oneshot(desc, action, false);
+}
+
+/*
  * Interrupt handler thread
  */
 static int irq_thread(void *data)
@@ -711,8 +748,15 @@ static int irq_thread(void *data)
         };
         struct irqaction *action = data;
         struct irq_desc *desc = irq_to_desc(action->irq);
+        void (*handler_fn)(struct irq_desc *desc, struct irqaction *action);
         int wake;
 
+        if (force_irqthreads & test_bit(IRQTF_FORCED_THREAD,
+                                        &action->thread_flags))
+                handler_fn = irq_forced_thread_fn;
+        else
+                handler_fn = irq_thread_fn;
+
         sched_setscheduler(current, SCHED_FIFO, &param);
         current->irqaction = action;
 
@@ -736,10 +780,7 @@ static int irq_thread(void *data)
                         raw_spin_unlock_irq(&desc->lock);
                 } else {
                         raw_spin_unlock_irq(&desc->lock);
-
-                        action->thread_fn(action->irq, action->dev_id);
-
-                        irq_finalize_oneshot(desc, action, false);
+                        handler_fn(desc, action);
                 }
 
                 wake = atomic_dec_and_test(&desc->threads_active);
@@ -789,6 +830,22 @@ void exit_irq_thread(void)
         set_bit(IRQTF_DIED, &tsk->irqaction->flags);
 }
 
+static void irq_setup_forced_threading(struct irqaction *new)
+{
+        if (!force_irqthreads)
+                return;
+        if (new->flags & (IRQF_NO_THREAD | IRQF_PERCPU | IRQF_ONESHOT))
+                return;
+
+        new->flags |= IRQF_ONESHOT;
+
+        if (!new->thread_fn) {
+                set_bit(IRQTF_FORCED_THREAD, &new->thread_flags);
+                new->thread_fn = new->handler;
+                new->handler = irq_default_primary_handler;
+        }
+}
+
 /*
  * Internal function to register an irqaction - typically used to
  * allocate special interrupts that are part of the architecture.
@@ -838,6 +895,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
                  * dummy function which warns when called.
                  */
                 new->handler = irq_nested_primary_handler;
+        } else {
+                irq_setup_forced_threading(new);
         }
 
         /*
diff --git a/kernel/softirq.c b/kernel/softirq.c
index c0490464e92f..a33fb2911248 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -311,9 +311,21 @@ void irq_enter(void)
 }
 
 #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
-# define invoke_softirq()       __do_softirq()
+static inline void invoke_softirq(void)
+{
+        if (!force_irqthreads)
+                __do_softirq();
+        else
+                wakeup_softirqd();
+}
 #else
-# define invoke_softirq()       do_softirq()
+static inline void invoke_softirq(void)
+{
+        if (!force_irqthreads)
+                do_softirq();
+        else
+                wakeup_softirqd();
+}
 #endif
 
 /*