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>
This commit is contained in:
Mark Fasheh 2008-04-10 13:55:21 -07:00 committed by Jonathan Corbet
parent d396c5f158
commit 14dadf1d5e
1 changed files with 22 additions and 0 deletions

View File

@ -5,6 +5,28 @@ Please use DEFINE_SPINLOCK()/DEFINE_RWLOCK() or
__SPIN_LOCK_UNLOCKED()/__RW_LOCK_UNLOCKED() as appropriate for static __SPIN_LOCK_UNLOCKED()/__RW_LOCK_UNLOCKED() as appropriate for static
initialization. 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 Dynamic initialization, when necessary, may be performed as
demonstrated below. demonstrated below.