linux-kernel - [PATCH] Add additional examples in Documentation/spinlocks.txt

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Message-ID: <20080410205520.GY21261@wotan.suse.de>
Date:	Thu, 10 Apr 2008 13:55:21 -0700
From:	Mark Fasheh <mfasheh@...e.com>
To:	Jon Corbet <corbet@....net>
Cc:	linux-kernel@...r.kernel.org,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] Add additional examples in Documentation/spinlocks.txt

Checkpatch will throw an error if code doesn't use the correct initializers
for static spinlocks:

ERROR: Use of SPIN_LOCK_UNLOCKED is deprecated: see Documentation/spinlocks.txt

This is fine, but Documentation/spinlocks.txt isn't very clear on how to
_use_ the new initializers for static variables. To save people time in the
future, I added two small examples of how to fix old-style static
initializers to be more lockdep friendly.

Signed-off-by: Mark Fasheh <mfasheh@...e.com>

diff --git a/Documentation/spinlocks.txt b/Documentation/spinlocks.txt
index 471e753..619699d 100644
--- a/Documentation/spinlocks.txt
+++ b/Documentation/spinlocks.txt
@@ -5,6 +5,28 @@ Please use DEFINE_SPINLOCK()/DEFINE_RWLOCK() or
 __SPIN_LOCK_UNLOCKED()/__RW_LOCK_UNLOCKED() as appropriate for static
 initialization.
 
+Most of the time, you can simply turn:
+
+	static spinlock_t xxx_lock = SPIN_LOCK_UNLOCKED;
+
+into:
+
+	static DEFINE_SPINLOCK(xxx_lock);
+
+Static structure member variables go from:
+
+	struct foo bar {
+		.lock	=	SPIN_LOCK_UNLOCKED;
+	};
+
+to:
+
+	struct foo bar {
+		.lock	=	__SPIN_LOCK_UNLOCKED(bar.lock);
+	};
+
+Declaration of static rw_locks undergo a similar transformation.
+
 Dynamic initialization, when necessary, may be performed as
 demonstrated below.
 
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