From e6c6e15b03639e98df68df35ba0f639bdbc1dc51 Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sat, 15 Aug 2015 18:30:28 +0200
Subject: kern: keep track of the writer when debugging locks

* configfrag.ac (MACH_LDEBUG): Adjust comment, we use it to sanity
check all locks now.
* kern/lock.c (lock_write): Keep track of the writer thread.
(lock_done): Clear writer.
(lock_read_to_write): Keep track of the writer thread.
(lock_write_to_read): Assert that the current thread holds the lock.
Clear writer.
(lock_try_write): Keep track of the writer thread.
(lock_try_read_to_write): Likewise.
(lock_set_recursive): Assert that the current thread holds the lock.
* kern/lock.h (struct lock): New field `writer'.
(have_read_lock, have_write_lock, have_lock): New macros that can be
used to assert that the current thread holds the given lock.  If
MACH_LDEBUG is not set, they evaluate to true.
---
 kern/lock.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'kern/lock.h')

diff --git a/kern/lock.h b/kern/lock.h
index e88e1824..2781a48a 100644
--- a/kern/lock.h
+++ b/kern/lock.h
@@ -174,6 +174,9 @@ struct lock {
 	/* boolean_t */	can_sleep:1,	/* Can attempts to lock go to sleep? */
 			recursion_depth:12, /* Depth of recursion */
 			:0; 
+#if MACH_LDEBUG
+	struct thread	*writer;
+#endif	/* MACH_LDEBUG */
 	decl_simple_lock_data(,interlock)
 					/* Hardware interlock field.
 					   Last in the structure so that
@@ -203,6 +206,17 @@ extern boolean_t	lock_try_read_to_write(lock_t);
 extern void		lock_set_recursive(lock_t);
 extern void		lock_clear_recursive(lock_t);
 
+/* Lock debugging support.  */
+#if	! MACH_LDEBUG
+#define have_read_lock(l)	1
+#define have_write_lock(l)	1
+#else	/* MACH_LDEBUG */
+/* XXX: We don't keep track of readers, so this is an approximation.  */
+#define have_read_lock(l)	((l)->read_count > 0)
+#define have_write_lock(l)	((l)->writer == current_thread())
+#endif	/* MACH_LDEBUG */
+#define have_lock(l)		(have_read_lock(l) || have_write_lock(l))
+
 void db_show_all_slocks(void);
 
 #endif	/* _KERN_LOCK_H_ */
-- 
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