softirq: Consolidate common code in tasklet_[hi]_action()

tasklet_action() + tasklet_hi_action() are almost identical.  Move the
common code from both function into __tasklet_action_common() and let
both functions invoke it with different arguments.

[ bigeasy: Splitted out from RT's "tasklet: Prevent tasklets from going
	   into infinite spin in RT" and added commit message]

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Julia Cartwright <juliac@eso.teric.us>
Link: https://lkml.kernel.org/r/20180227164808.10093-3-bigeasy@linutronix.de

1 files changed, 15 insertions, 39 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 2394b009994f..177de3640c78 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -490,14 +490,16 @@ void __tasklet_hi_schedule(struct tasklet_struct *t)
 }
 EXPORT_SYMBOL(__tasklet_hi_schedule);
 
-static __latent_entropy void tasklet_action(struct softirq_action *a)
+static void tasklet_action_common(struct softirq_action *a,
+                                  struct tasklet_head *tl_head,
+                                  unsigned int softirq_nr)
 {
         struct tasklet_struct *list;
 
         local_irq_disable();
-        list = __this_cpu_read(tasklet_vec.head);
-        __this_cpu_write(tasklet_vec.head, NULL);
-        __this_cpu_write(tasklet_vec.tail, this_cpu_ptr(&tasklet_vec.head));
+        list = tl_head->head;
+        tl_head->head = NULL;
+        tl_head->tail = &tl_head->head;
         local_irq_enable();
 
         while (list) {
@@ -519,47 +521,21 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
 
                 local_irq_disable();
                 t->next = NULL;
-                *__this_cpu_read(tasklet_vec.tail) = t;
-                __this_cpu_write(tasklet_vec.tail, &(t->next));
-                __raise_softirq_irqoff(TASKLET_SOFTIRQ);
+                *tl_head->tail = t;
+                tl_head->tail = &t->next;
+                __raise_softirq_irqoff(softirq_nr);
                 local_irq_enable();
         }
 }
 
-static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
+static __latent_entropy void tasklet_action(struct softirq_action *a)
 {
-        struct tasklet_struct *list;
-
-        local_irq_disable();
-        list = __this_cpu_read(tasklet_hi_vec.head);
-        __this_cpu_write(tasklet_hi_vec.head, NULL);
-        __this_cpu_write(tasklet_hi_vec.tail, this_cpu_ptr(&tasklet_hi_vec.head));
-        local_irq_enable();
-
-        while (list) {
-                struct tasklet_struct *t = list;
-
-                list = list->next;
-
-                if (tasklet_trylock(t)) {
-                        if (!atomic_read(&t->count)) {
-                                if (!test_and_clear_bit(TASKLET_STATE_SCHED,
-                                                        &t->state))
-                                        BUG();
-                                t->func(t->data);
-                                tasklet_unlock(t);
-                                continue;
-                        }
-                        tasklet_unlock(t);
-                }
+        tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
+}
 
-                local_irq_disable();
-                t->next = NULL;
-                *__this_cpu_read(tasklet_hi_vec.tail) = t;
-                __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
-                __raise_softirq_irqoff(HI_SOFTIRQ);
-                local_irq_enable();
-        }
+static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
+{
+        tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
 }
 
 void tasklet_init(struct tasklet_struct *t,