linux-kernel - [PATCH 2/7] static_key: add static_key_slow_inc

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Date:	Thu, 17 Oct 2013 12:10:25 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Radim Krčmář <rkrcmar@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Andrew Jones <drjones@...hat.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 2/7] static_key: add static_key_slow_inc_deferred()

We can cancel deferred static_key_slow_dec() instead of increasing
.enabled.counter.

Timer now won't fire before 'timeout' since last increase, so this patch
further stabilizes the case of frequent switching.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 include/linux/jump_label_ratelimit.h | 5 +++++
 kernel/jump_label.c                  | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/jump_label_ratelimit.h b/include/linux/jump_label_ratelimit.h
index 1137883..e2fa2e7 100644
--- a/include/linux/jump_label_ratelimit.h
+++ b/include/linux/jump_label_ratelimit.h
@@ -13,6 +13,7 @@ struct static_key_deferred {
 #endif
 
 #ifdef HAVE_JUMP_LABEL
+extern void static_key_slow_inc_deferred(struct static_key_deferred *key);
 extern void static_key_slow_dec_deferred(struct static_key_deferred *key);
 extern void
 jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl);
@@ -21,6 +22,10 @@ jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl);
 struct static_key_deferred {
 	struct static_key  key;
 };
+static inline void static_key_slow_inc_deferred(struct static_key_deferred *key)
+{
+	static_key_slow_inc(&key->key);
+}
 static inline void static_key_slow_dec_deferred(struct static_key_deferred *key)
 {
 	static_key_slow_dec(&key->key);
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 7018042..ff67257 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -73,6 +73,13 @@ void static_key_slow_inc(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 
+void static_key_slow_inc_deferred(struct static_key_deferred *key)
+{
+	if (!cancel_delayed_work(&key->work))
+		static_key_slow_inc(&key->key);
+}
+EXPORT_SYMBOL_GPL(static_key_slow_inc_deferred);
+
 static void __static_key_slow_dec(struct static_key *key,
 		unsigned long rate_limit, struct delayed_work *work)
 {
-- 
1.8.3.1

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