[PATCH RT] blk-mq: revert raw locks, post pone notifier to POST_DEAD

[Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>]

The blk_mq_cpu_notify_lock should be raw because some CPU down levels
are called with interrupts off. The notifier itself calls currently one
function that is blk_mq_hctx_notify().
That function acquires the ctx->lock lock which is sleeping and I would
prefer to keep it that way. That function only moves IO-requests from
the CPU that is going offline to another CPU and it is currently the
only one. Therefore I revert the list lock back to sleeping spinlocks
and let the notifier run at POST_DEAD time.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
Mike, I see that lockdep splat (sleeping while atomic) during cpu-hotplug.
Don't you see this, too?

 block/blk-mq-cpu.c | 17 ++++++++++-------
 block/blk-mq.c     |  2 +-
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/block/blk-mq-cpu.c b/block/blk-mq-cpu.c
index 136ef86..37acc3a 100644
--- a/block/blk-mq-cpu.c
+++ b/block/blk-mq-cpu.c
@@ -11,7 +11,7 @@
 #include "blk-mq.h"
 
 static LIST_HEAD(blk_mq_cpu_notify_list);
-static DEFINE_RAW_SPINLOCK(blk_mq_cpu_notify_lock);
+static DEFINE_SPINLOCK(blk_mq_cpu_notify_lock);
 
 static int blk_mq_main_cpu_notify(struct notifier_block *self,
 				  unsigned long action, void *hcpu)
@@ -19,12 +19,15 @@ static int blk_mq_main_cpu_notify(struct notifier_block *self,
 	unsigned int cpu = (unsigned long) hcpu;
 	struct blk_mq_cpu_notifier *notify;
 
-	raw_spin_lock(&blk_mq_cpu_notify_lock);
+	if (action != CPU_POST_DEAD && action != CPU_POST_DEAD)
+		return NOTIFY_OK;
+
+	spin_lock(&blk_mq_cpu_notify_lock);
 
 	list_for_each_entry(notify, &blk_mq_cpu_notify_list, list)
 		notify->notify(notify->data, action, cpu);
 
-	raw_spin_unlock(&blk_mq_cpu_notify_lock);
+	spin_unlock(&blk_mq_cpu_notify_lock);
 	return NOTIFY_OK;
 }
 
@@ -32,16 +35,16 @@ void blk_mq_register_cpu_notifier(struct blk_mq_cpu_notifier *notifier)
 {
 	BUG_ON(!notifier->notify);
 
-	raw_spin_lock(&blk_mq_cpu_notify_lock);
+	spin_lock(&blk_mq_cpu_notify_lock);
 	list_add_tail(&notifier->list, &blk_mq_cpu_notify_list);
-	raw_spin_unlock(&blk_mq_cpu_notify_lock);
+	spin_unlock(&blk_mq_cpu_notify_lock);
 }
 
 void blk_mq_unregister_cpu_notifier(struct blk_mq_cpu_notifier *notifier)
 {
-	raw_spin_lock(&blk_mq_cpu_notify_lock);
+	spin_lock(&blk_mq_cpu_notify_lock);
 	list_del(&notifier->list);
-	raw_spin_unlock(&blk_mq_cpu_notify_lock);
+	spin_unlock(&blk_mq_cpu_notify_lock);
 }
 
 void blk_mq_init_cpu_notifier(struct blk_mq_cpu_notifier *notifier,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index da3af9f..d5e73d8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -971,7 +971,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action,
 	struct blk_mq_ctx *ctx;
 	LIST_HEAD(tmp);
 
-	if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
+	if (action != CPU_POST_DEAD && action != CPU_POST_DEAD)
 		return;
 
 	/*
-- 
2.0.0.rc0

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