[RFC patch V2 4/7] softirq: Use hotplug thread infrastructure

Thomas Gleixner
2012-06-15T14:13:27Z

[-- Attachment #1: softirq-use-smboot-threads.patch --]
[-- Type: text/plain, Size: 3945 bytes --]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/softirq.c | 84 +++++++++++--------------------------------------------
1 file changed, 18 insertions(+), 66 deletions(-)

Index: tip/kernel/softirq.c
===================================================================
--- tip.orig/kernel/softirq.c
+++ tip/kernel/softirq.c
@@ -23,6 +23,7 @@
#include <linux/rcupdate.h>
#include <linux/ftrace.h>
#include <linux/smp.h>
+#include <linux/smpboot.h>
#include <linux/tick.h>

#define CREATE_TRACE_POINTS
@@ -733,24 +734,17 @@ void __init softirq_init(void)
open_softirq(HI_SOFTIRQ, tasklet_hi_action);
}

-static int run_ksoftirqd(void * __bind_cpu)
+static int run_ksoftirqd(void *td)
{
- set_current_state(TASK_INTERRUPTIBLE);
-
- while (!kthread_should_stop()) {
+ while (!smpboot_thread_check_parking(td)) {
+ set_current_state(TASK_INTERRUPTIBLE);
preempt_disable();
- if (!local_softirq_pending()) {
+ if (!local_softirq_pending())
schedule_preempt_disabled();
- }

__set_current_state(TASK_RUNNING);

while (local_softirq_pending()) {
- /* Preempt disable stops cpu going offline.
- If already offline, we'll be on wrong CPU:
- don't process */
- if (cpu_is_offline((long)__bind_cpu))
- goto wait_to_die;
local_irq_disable();
if (local_softirq_pending())
__do_softirq();
@@ -758,23 +752,10 @@ static int run_ksoftirqd(void * __bind_c
sched_preempt_enable_no_resched();
cond_resched();
preempt_disable();
- rcu_note_context_switch((long)__bind_cpu);
+ rcu_note_context_switch(smp_processor_id());
}
preempt_enable();
- set_current_state(TASK_INTERRUPTIBLE);
}
- __set_current_state(TASK_RUNNING);
- return 0;
-
-wait_to_die:
- preempt_enable();
- /* Wait for kthread_stop */
- set_current_state(TASK_INTERRUPTIBLE);
- while (!kthread_should_stop()) {
- schedule();
- set_current_state(TASK_INTERRUPTIBLE);
- }
- __set_current_state(TASK_RUNNING);
return 0;
}

@@ -841,50 +822,17 @@ static int __cpuinit cpu_callback(struct
unsigned long action,
void *hcpu)
{
- int hotcpu = (unsigned long)hcpu;
- struct task_struct *p;
-
switch (action) {
- case CPU_UP_PREPARE:
- case CPU_UP_PREPARE_FROZEN:
- p = kthread_create_on_node(run_ksoftirqd,
- hcpu,
- cpu_to_node(hotcpu),
- "ksoftirqd/%d", hotcpu);
- if (IS_ERR(p)) {
- printk("ksoftirqd for %i failed\n", hotcpu);
- return notifier_from_errno(PTR_ERR(p));
- }
- kthread_bind(p, hotcpu);
- per_cpu(ksoftirqd, hotcpu) = p;
- break;
- case CPU_ONLINE:
- case CPU_ONLINE_FROZEN:
- wake_up_process(per_cpu(ksoftirqd, hotcpu));
- break;
#ifdef CONFIG_HOTPLUG_CPU
- case CPU_UP_CANCELED:
- case CPU_UP_CANCELED_FROZEN:
- if (!per_cpu(ksoftirqd, hotcpu))
- break;
- /* Unbind so it can run. Fall thru. */
- kthread_bind(per_cpu(ksoftirqd, hotcpu),
- cpumask_any(cpu_online_mask));
case CPU_DEAD:
case CPU_DEAD_FROZEN: {
- static const struct sched_param param = {
- .sched_priority = MAX_RT_PRIO-1
- };
-
- p = per_cpu(ksoftirqd, hotcpu);
- per_cpu(ksoftirqd, hotcpu) = NULL;
- sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
- kthread_stop(p);
+ int hotcpu = (unsigned long)hcpu;
+
takeover_tasklets(hotcpu);
break;
}
#endif /* CONFIG_HOTPLUG_CPU */
- }
+ }
return NOTIFY_OK;
}

@@ -892,14 +840,18 @@ static struct notifier_block __cpuinitda
.notifier_call = cpu_callback
};

+static struct smp_hotplug_thread softirq_threads = {
+ .store = &ksoftirqd,
+ .thread_fn = run_ksoftirqd,
+ .thread_comm = "ksoftirqd/%u",
+};
+
static __init int spawn_ksoftirqd(void)
{
- void *cpu = (void *)(long)smp_processor_id();
- int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
-
- BUG_ON(err != NOTIFY_OK);
- cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
register_cpu_notifier(&cpu_nfb);
+
+ BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
+
return 0;
}
early_initcall(spawn_ksoftirqd);