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@suse.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>

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@suse.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Mark Fasheh · Jonathan Corbet
1 parent d396c5f158
Showing 1 changed file with 22 additions and 0 deletions Side-by-side Diff
Documentation/spinlocks.txt
@@ -5,6 +5,28 @@
 __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.
...	...	@@ -5,6 +5,28 @@
5	5	__SPIN_LOCK_UNLOCKED()/__RW_LOCK_UNLOCKED() as appropriate for static
6	6	initialization.
7	7
	8	+Most of the time, you can simply turn:
	9	+
	10	+ static spinlock_t xxx_lock = SPIN_LOCK_UNLOCKED;
	11	+
	12	+into:
	13	+
	14	+ static DEFINE_SPINLOCK(xxx_lock);
	15	+
	16	+Static structure member variables go from:
	17	+
	18	+ struct foo bar {
	19	+ .lock = SPIN_LOCK_UNLOCKED;
	20	+ };
	21	+
	22	+to:
	23	+
	24	+ struct foo bar {
	25	+ .lock = __SPIN_LOCK_UNLOCKED(bar.lock);
	26	+ };
	27	+
	28	+Declaration of static rw_locks undergo a similar transformation.
	29	+
8	30	Dynamic initialization, when necessary, may be performed as
9	31	demonstrated below.
10	32