linux-kernel - [PATCH 2/2] kernel/sofirq: consolidate common code in tasklet_action() + tasklet_hi

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Date:   Tue, 27 Feb 2018 17:48:08 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     mingo@...nel.org
Cc:     linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        tglx@...utronix.de, Julia Cartwright <juliac@....teric.us>,
        Ingo Molnar <mingo@...e.hu>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 2/2] kernel/sofirq: consolidate common code in tasklet_action() + tasklet_hi_action()

From: Ingo Molnar <mingo@...e.hu>

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

Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
[bigeasy: splitted out from RT's "tasklet: Prevent tasklets from going
into infinite spin in RT" and added commit message]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/softirq.c | 54 +++++++++++++++---------------------------------------
 1 file 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_action(struct softirq_action *a)
+{
+	tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
+}
+
 static __latent_entropy void tasklet_hi_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);
-		}
-
-		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();
-	}
+	tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
 }
 
 void tasklet_init(struct tasklet_struct *t,
-- 
2.16.2