linux-kernel - [PATCH RFC 02/13] rwlock_t: Implement double_write

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Date:	Mon, 25 May 2015 20:44:19 +0300
From:	Kirill Tkhai <ktkhai@...n.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	"Peter Zijlstra" <peterz@...radead.org>,
	Michal Hocko <mhocko@...e.cz>,
	"Rik van Riel" <riel@...hat.com>,
	Ionut Alexa <ionut.m.alexa@...il.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Kirill Tkhai <tkhai@...dex.ru>
Subject: [PATCH RFC 02/13] rwlock_t: Implement double_write_{,un}lock()

New helpers for locking two locks at a time.

Signed-off-by: Kirill Tkhai <ktkhai@...n.com>
---
 include/linux/spinlock.h |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index 3e18379..e1e3054 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -426,4 +426,23 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 #define atomic_dec_and_lock(atomic, lock) \
 		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 
+static inline void double_write_lock(rwlock_t *lock1, rwlock_t *lock2)
+{
+	if (lock1 < lock2) {
+		write_lock(lock1);
+		write_lock(lock2);
+	} else if (lock1 > lock2) {
+		write_lock(lock2);
+		write_lock(lock1);
+	} else {
+		write_lock(lock1);
+	}
+}
+static inline void double_write_unlock(rwlock_t *lock1, rwlock_t *lock2)
+{
+	if (lock2 != lock1)
+		write_unlock(lock2);
+	write_unlock(lock1);
+}
+
 #endif /* __LINUX_SPINLOCK_H */



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