linux-kernel - [PATCH 08/21] block: softirq: Convert to hotplug state machine

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Date:   Tue,  6 Sep 2016 19:04:44 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, rt@...utronix.de,
        tglx@...utronix.de,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 08/21] block: softirq: Convert to hotplug state machine

Install the callbacks via the state machine.

Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 block/blk-softirq.c        | 27 ++++++++++-----------------
 include/linux/cpuhotplug.h |  1 +
 2 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 53b1737e978d..96631e6a22b9 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -78,30 +78,21 @@ static int raise_blk_irq(int cpu, struct request *rq)
 }
 #endif
 
-static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
-			  void *hcpu)
+static int blk_softirq_cpu_dead(unsigned int cpu)
 {
 	/*
 	 * If a CPU goes away, splice its entries to the current CPU
 	 * and trigger a run of the softirq
 	 */
-	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
-		int cpu = (unsigned long) hcpu;
+	local_irq_disable();
+	list_splice_init(&per_cpu(blk_cpu_done, cpu),
+			 this_cpu_ptr(&blk_cpu_done));
+	raise_softirq_irqoff(BLOCK_SOFTIRQ);
+	local_irq_enable();
 
-		local_irq_disable();
-		list_splice_init(&per_cpu(blk_cpu_done, cpu),
-				 this_cpu_ptr(&blk_cpu_done));
-		raise_softirq_irqoff(BLOCK_SOFTIRQ);
-		local_irq_enable();
-	}
-
-	return NOTIFY_OK;
+	return 0;
 }
 
-static struct notifier_block blk_cpu_notifier = {
-	.notifier_call	= blk_cpu_notify,
-};
-
 void __blk_complete_request(struct request *req)
 {
 	int ccpu, cpu;
@@ -180,7 +171,9 @@ static __init int blk_softirq_init(void)
 		INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
 
 	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
-	register_hotcpu_notifier(&blk_cpu_notifier);
+	cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
+				  "block/softirq:dead", NULL,
+				  blk_softirq_cpu_dead);
 	return 0;
 }
 subsys_initcall(blk_softirq_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index be6c01b7efbe..a12044828e03 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -23,6 +23,7 @@ enum cpuhp_state {
 	CPUHP_ARM64_FPSIMD_DEAD,
 	CPUHP_ARM_OMAP_WAKE_DEAD,
 	CPUHP_IRQ_POLL_DEAD,
+	CPUHP_BLOCK_SOFTIRQ_DEAD,
 	CPUHP_WORKQUEUE_PREP,
 	CPUHP_POWER_NUMA_PREPARE,
 	CPUHP_HRTIMERS_PREPARE,
-- 
2.9.3