2 files changed, 20 insertions, 4 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index af2cc6eabcc7..ad95133f8fae 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -390,6 +390,16 @@ config HAVE_UNDERSCORE_SYMBOL_PREFIX
           Some architectures generate an _ in front of C symbols; things like
           module loading and assembly files need to know about this.
 
+config HAVE_IRQ_EXIT_ON_IRQ_STACK
+        bool
+        help
+          Architecture doesn't only execute the irq handler on the irq stack
+          but also irq_exit(). This way we can process softirqs on this irq
+          stack instead of switching to a new one when we call __do_softirq()
+          in the end of an hardirq.
+          This spares a stack switch and improves cache usage on softirq
+          processing.
+
 #
 # ABI hall of shame
 #
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 2b4328ea769f..dacd0ab51df4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -332,15 +332,21 @@ void irq_enter(void)
 static inline void invoke_softirq(void)
 {
         if (!force_irqthreads) {
+#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
                 /*
                  * We can safely execute softirq on the current stack if
                  * it is the irq stack, because it should be near empty
-                 * at this stage. But we have no way to know if the arch
-                 * calls irq_exit() on the irq stack. So call softirq
-                 * in its own stack to prevent from any overrun on top
-                 * of a potentially deep task stack.
+                 * at this stage.
+                 */
+                __do_softirq();
+#else
+                /*
+                 * Otherwise, irq_exit() is called on the task stack that can
+                 * be potentially deep already. So call softirq in its own stack
+                 * to prevent from any overrun.
                  */
                 do_softirq_own_stack();
+#endif
         } else {
                 wakeup_softirqd();
         }