path: root/sys/sys/lock.h
diff options
authorJohn Baldwin <jhb@FreeBSD.org>2007-03-09 16:27:11 +0000
committerJohn Baldwin <jhb@FreeBSD.org>2007-03-09 16:27:11 +0000
commit6e21afd40ca27a1aaef83296fa1e46fbc5e48017 (patch)
tree71366da8c5df1e7210aad9d816166233c0107eff /sys/sys/lock.h
parentf9feee175baa10825785cf7f2e596170612ae15d (diff)
Add two new function pointers 'lc_lock' and 'lc_unlock' to lock classes.
These functions are intended to be used to drop a lock and then reacquire it when doing an sleep such as msleep(9). Both functions accept a 'struct lock_object *' as their first parameter. The 'lc_unlock' function returns an integer that is then passed as the second paramter to the subsequent 'lc_lock' function. This can be used to communicate state. For example, sx locks and rwlocks use this to indicate if the lock was share/read locked vs exclusive/write locked. Currently, spin mutexes and lockmgr locks do not provide working lc_lock and lc_unlock functions.
Notes: svn path=/head/; revision=167368
Diffstat (limited to 'sys/sys/lock.h')
1 files changed, 9 insertions, 0 deletions
diff --git a/sys/sys/lock.h b/sys/sys/lock.h
index a30a595f03c6..3a3b4d28a3b8 100644
--- a/sys/sys/lock.h
+++ b/sys/sys/lock.h
@@ -45,12 +45,21 @@ struct thread;
* an error to perform any type of context switch while holding a spin lock.
* Also, for an individual lock to be recursable, its class must allow
* recursion and the lock itself must explicitly allow recursion.
+ *
+ * The 'lc_ddb_show' function pointer is used to dump class-specific
+ * data for the 'show lock' DDB command. The 'lc_lock' and
+ * 'lc_unlock' function pointers are used in sleep(9) and cv_wait(9)
+ * to lock and unlock locks while blocking on a sleep queue. The
+ * return value of 'lc_unlock' will be passed to 'lc_lock' on resume
+ * to allow communication of state between the two routines.
struct lock_class {
const char *lc_name;
u_int lc_flags;
void (*lc_ddb_show)(struct lock_object *lock);
+ void (*lc_lock)(struct lock_object *lock, int how);
+ int (*lc_unlock)(struct lock_object *lock);
#define LC_SLEEPLOCK 0x00000001 /* Sleep lock. */