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authorEd L. Cashin <ecashin@coraid.com>2007-07-15 23:41:50 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-16 09:05:52 -0700
commit017f021c7e5fe3f82ccc5cbb7b1750e66e00f527 (patch)
tree755a3f0f15a4adc1254ebb2ed1497afcf406ba55
parent7e7d136e9e083f04b859411248c699cbb89e418d (diff)
downloadlinux-bcache-017f021c7e5fe3f82ccc5cbb7b1750e66e00f527.tar.zst
docs: static initialization of spinlocks is OK
Static initialization of spinlocks is preferable to dynamic initialization when it is practical. This patch updates documentation for consistency with comments in spinlock_types.h. Signed-off-by: Ed L. Cashin <ecashin@coraid.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/spinlocks.txt20
1 files changed, 11 insertions, 9 deletions
diff --git a/Documentation/spinlocks.txt b/Documentation/spinlocks.txt
index a661d684768e..471e75389778 100644
--- a/Documentation/spinlocks.txt
+++ b/Documentation/spinlocks.txt
@@ -1,7 +1,12 @@
-UPDATE March 21 2005 Amit Gud <gud@eth.net>
+SPIN_LOCK_UNLOCKED and RW_LOCK_UNLOCKED defeat lockdep state tracking and
+are hence deprecated.
-Macros SPIN_LOCK_UNLOCKED and RW_LOCK_UNLOCKED are deprecated and will be
-removed soon. So for any new code dynamic initialization should be used:
+Please use DEFINE_SPINLOCK()/DEFINE_RWLOCK() or
+__SPIN_LOCK_UNLOCKED()/__RW_LOCK_UNLOCKED() as appropriate for static
+initialization.
+
+Dynamic initialization, when necessary, may be performed as
+demonstrated below.
spinlock_t xxx_lock;
rwlock_t xxx_rw_lock;
@@ -15,12 +20,9 @@ removed soon. So for any new code dynamic initialization should be used:
module_init(xxx_init);
-Reasons for deprecation
- - it hurts automatic lock validators
- - it becomes intrusive for the realtime preemption patches
-
-Following discussion is still valid, however, with the dynamic initialization
-of spinlocks instead of static.
+The following discussion is still valid, however, with the dynamic
+initialization of spinlocks or with DEFINE_SPINLOCK, etc., used
+instead of SPIN_LOCK_UNLOCKED.
-----------------------