[PATCH 1/2] kernel/sofirq: consolidate common code in __tasklet_schedule() + _hi_

From: Sebastian Andrzej Siewior
Date: Tue Feb 27 2018 - 11:49:37 EST


From: Ingo Molnar <mingo@xxxxxxx>

__tasklet_schedule() and __tasklet_hi_schedule() 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@xxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bigeasy: splitted out from RT's "tasklet: Prevent tasklets from going
into infinite spin in RT" and added commit message. Do
this_cpu_ptr(headp) in __tasklet_schedule_common() as suggested by Julia
Cartwright]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
kernel/softirq.c | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 24d243ef8e71..2394b009994f 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -460,29 +460,33 @@ struct tasklet_head {
static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);

-void __tasklet_schedule(struct tasklet_struct *t)
+static void __tasklet_schedule_common(struct tasklet_struct *t,
+ struct tasklet_head __percpu *headp,
+ unsigned int softirq_nr)
{
+ struct tasklet_head *head;
unsigned long flags;

local_irq_save(flags);
+ head = this_cpu_ptr(headp);
t->next = NULL;
- *__this_cpu_read(tasklet_vec.tail) = t;
- __this_cpu_write(tasklet_vec.tail, &(t->next));
- raise_softirq_irqoff(TASKLET_SOFTIRQ);
+ *head->tail = t;
+ head->tail = &(t->next);
+ raise_softirq_irqoff(softirq_nr);
local_irq_restore(flags);
}
+
+void __tasklet_schedule(struct tasklet_struct *t)
+{
+ __tasklet_schedule_common(t, &tasklet_vec,
+ TASKLET_SOFTIRQ);
+}
EXPORT_SYMBOL(__tasklet_schedule);

void __tasklet_hi_schedule(struct tasklet_struct *t)
{
- unsigned long flags;
-
- local_irq_save(flags);
- 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_restore(flags);
+ __tasklet_schedule_common(t, &tasklet_hi_vec,
+ HI_SOFTIRQ);
}
EXPORT_SYMBOL(__tasklet_hi_schedule);

--
2.16.2