irq_work: Make self-IPIs optable

[karo-tx-linux.git] / kernel / irq_work.c

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 480f74715ba97b0d4885baf4892e0abcbe803eef..7f3a59bc8e3d97660a8e75fdf6847fd4124f96c6 100644 (file)
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -12,24 +12,15 @@
 #include <linux/percpu.h>
 #include <linux/hardirq.h>
 #include <linux/irqflags.h>
+#include <linux/sched.h>
+#include <linux/tick.h>
 #include <linux/cpu.h>
 #include <linux/notifier.h>
 #include <asm/processor.h>
 
-/*
- * An entry can be in one of four states:
- *
- * free             NULL, 0 -> {claimed}       : free to be used
- * claimed   NULL, 3 -> {pending}       : claimed to be enqueued
- * pending   next, 3 -> {busy}          : queued, pending callback
- * busy      NULL, 2 -> {free, claimed} : callback in progress, can be claimed
- */
-
-#define IRQ_WORK_PENDING       1UL
-#define IRQ_WORK_BUSY          2UL
-#define IRQ_WORK_FLAGS         3UL
 
 static DEFINE_PER_CPU(struct llist_head, irq_work_list);
+static DEFINE_PER_CPU(int, irq_work_raised);
 
 /*
  * Claim the entry so that no one else will poke at it.
@@ -69,14 +60,19 @@ void __weak arch_irq_work_raise(void)
  */
 static void __irq_work_queue(struct irq_work *work)
 {
-       bool empty;
-
        preempt_disable();
 
-       empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
-       /* The list was empty, raise self-interrupt to start processing. */
-       if (empty)
-               arch_irq_work_raise();
+       llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
+
+       /*
+        * If the work is not "lazy" or the tick is stopped, raise the irq
+        * work interrupt (if supported by the arch), otherwise, just wait
+        * for the next tick.
+        */
+       if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {
+               if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))
+                       arch_irq_work_raise();
+       }
 
        preempt_enable();
 }
@@ -117,10 +113,19 @@ bool irq_work_needs_cpu(void)
 
 static void __irq_work_run(void)
 {
+       unsigned long flags;
        struct irq_work *work;
        struct llist_head *this_list;
        struct llist_node *llnode;
 
+
+       /*
+        * Reset the "raised" state right before we check the list because
+        * an NMI may enqueue after we find the list empty from the runner.
+        */
+       __this_cpu_write(irq_work_raised, 0);
+       barrier();
+
        this_list = &__get_cpu_var(irq_work_list);
        if (llist_empty(this_list))
                return;
@@ -140,13 +145,15 @@ static void __irq_work_run(void)
                 * to claim that work don't rely on us to handle their data
                 * while we are in the middle of the func.
                 */
-               xchg(&work->flags, IRQ_WORK_BUSY);
+               flags = work->flags & ~IRQ_WORK_PENDING;
+               xchg(&work->flags, flags);
+
                work->func(work);
                /*
                 * Clear the BUSY bit and return to the free state if
                 * no-one else claimed it meanwhile.
                 */
-               (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
+               (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
        }
 }