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Subject[tip:smp/hotplug] kernel/softirq: Convert to hotplug state machine
Commit-ID:  c4544dbc7a9bce3da6fa2361cd68cadb34e9221f
Gitweb: http://git.kernel.org/tip/c4544dbc7a9bce3da6fa2361cd68cadb34e9221f
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 18 Aug 2016 14:57:21 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 6 Sep 2016 18:30:22 +0200

kernel/softirq: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160818125731.27256-7-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
include/linux/cpuhotplug.h | 1 +
kernel/softirq.c | 27 ++++++---------------------
2 files changed, 7 insertions(+), 21 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 854e59a..a421407 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -17,6 +17,7 @@ enum cpuhp_state {
CPUHP_VIRT_NET_DEAD,
CPUHP_SLUB_DEAD,
CPUHP_MM_WRITEBACK_DEAD,
+ CPUHP_SOFTIRQ_DEAD,
CPUHP_WORKQUEUE_PREP,
CPUHP_POWER_NUMA_PREPARE,
CPUHP_HRTIMERS_PREPARE,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 17caf4b..c372114 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -700,7 +700,7 @@ void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
BUG();
}

-static void takeover_tasklets(unsigned int cpu)
+static int takeover_tasklets(unsigned int cpu)
{
/* CPU is dead, so no lock needed. */
local_irq_disable();
@@ -723,27 +723,12 @@ static void takeover_tasklets(unsigned int cpu)
raise_softirq_irqoff(HI_SOFTIRQ);

local_irq_enable();
+ return 0;
}
+#else
+#define takeover_tasklets NULL
#endif /* CONFIG_HOTPLUG_CPU */

-static int cpu_callback(struct notifier_block *nfb, unsigned long action,
- void *hcpu)
-{
- switch (action) {
-#ifdef CONFIG_HOTPLUG_CPU
- case CPU_DEAD:
- case CPU_DEAD_FROZEN:
- takeover_tasklets((unsigned long)hcpu);
- break;
-#endif /* CONFIG_HOTPLUG_CPU */
- }
- return NOTIFY_OK;
-}
-
-static struct notifier_block cpu_nfb = {
- .notifier_call = cpu_callback
-};
-
static struct smp_hotplug_thread softirq_threads = {
.store = &ksoftirqd,
.thread_should_run = ksoftirqd_should_run,
@@ -753,8 +738,8 @@ static struct smp_hotplug_thread softirq_threads = {

static __init int spawn_ksoftirqd(void)
{
- register_cpu_notifier(&cpu_nfb);
-
+ cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
+ takeover_tasklets);
BUG_ON(smpboot_register_percpu_thread(&softirq_threads));

return 0;
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