softirq: Use hotplug thread infrastructure

[ paulmck: Call rcu_note_context_switch() with interrupts enabled. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20120716103948.456416747@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 27 insertions, 84 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index b73e681df09e..5c6a5bd8462f 100644
--- a/kernel/softirq.c
+++ b/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
@@ -742,49 +743,22 @@ void __init softirq_init(void)
         open_softirq(HI_SOFTIRQ, tasklet_hi_action);
 }
 
-static int run_ksoftirqd(void * __bind_cpu)
+static int ksoftirqd_should_run(unsigned int cpu)
 {
-        set_current_state(TASK_INTERRUPTIBLE);
-
-        while (!kthread_should_stop()) {
-                preempt_disable();
-                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();
-                        local_irq_enable();
-                        sched_preempt_enable_no_resched();
-                        cond_resched();
-                        preempt_disable();
-                        rcu_note_context_switch((long)__bind_cpu);
-                }
-                preempt_enable();
-                set_current_state(TASK_INTERRUPTIBLE);
-        }
-        __set_current_state(TASK_RUNNING);
-        return 0;
+        return local_softirq_pending();
+}
 
-wait_to_die:
-        preempt_enable();
-        /* Wait for kthread_stop */
-        set_current_state(TASK_INTERRUPTIBLE);
-        while (!kthread_should_stop()) {
-                schedule();
-                set_current_state(TASK_INTERRUPTIBLE);
+static void run_ksoftirqd(unsigned int cpu)
+{
+        local_irq_disable();
+        if (local_softirq_pending()) {
+                __do_softirq();
+                rcu_note_context_switch(cpu);
+                local_irq_enable();
+                cond_resched();
+                return;
         }
-        __set_current_state(TASK_RUNNING);
-        return 0;
+        local_irq_enable();
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -850,50 +824,14 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb,
                                   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);
-                takeover_tasklets(hotcpu);
+        case CPU_DEAD_FROZEN:
+                takeover_tasklets((unsigned long)hcpu);
                 break;
-        }
 #endif /* CONFIG_HOTPLUG_CPU */
-        }
+        }
         return NOTIFY_OK;
 }
 
@@ -901,14 +839,19 @@ static struct notifier_block __cpuinitdata cpu_nfb = {
         .notifier_call = cpu_callback
 };
 
+static struct smp_hotplug_thread softirq_threads = {
+        .store                  = &ksoftirqd,
+        .thread_should_run      = ksoftirqd_should_run,
+        .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);