PERFORCE change 102584 for review

[John Baldwin]

http://perforce.freebsd.org/chv.cgi?CH=102584

Change 102584 by jhb at jhb_mutex on 2006/07/27 19:25:38

	Explicitly write a trash value that will always force any mtx_lock()
	operations to block into a mutex when it is being destroyed.
	Previously, the mutex operations on the mutex would actually still
	work, and if a lock was destroyed while it was held, then it would
	look like the lock was still held by the thread that destroyed it.

Affected files ...

.. //depot/projects/smpng/sys/kern/kern_mutex.c#132 edit
.. //depot/projects/smpng/sys/modules/crash/crash.c#33 edit
.. //depot/projects/smpng/sys/sys/mutex.h#64 edit

Differences ...

==== //depot/projects/smpng/sys/kern/kern_mutex.c#132 (text+ko) ====

@@ -276,6 +276,8 @@
 {
 
 	MPASS(curthread != NULL);
+	KASSERT(m->mtx_lock != MTX_DESTROYED,
+	    ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
 	KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep,
 	    ("mtx_lock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name,
 	    file, line));
@@ -302,6 +304,8 @@
 {
 
 	MPASS(curthread != NULL);
+	KASSERT(m->mtx_lock != MTX_DESTROYED,
+	    ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
 	KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep,
 	    ("mtx_unlock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name,
 	    file, line));
@@ -382,6 +386,8 @@
 {
 
 	MPASS(curthread != NULL);
+	KASSERT(m->mtx_lock != MTX_DESTROYED,
+	    ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
 	KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin,
 	    ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
 	    m->mtx_object.lo_name, file, line));
@@ -398,6 +404,8 @@
 {
 
 	MPASS(curthread != NULL);
+	KASSERT(m->mtx_lock != MTX_DESTROYED,
+	    ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
 	KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_spin,
 	    ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
 	    m->mtx_object.lo_name, file, line));
@@ -419,6 +427,8 @@
 	int rval;
 
 	MPASS(curthread != NULL);
+	KASSERT(m->mtx_lock != MTX_DESTROYED,
+	    ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
 	KASSERT(LOCK_CLASS(&m->mtx_object) == &lock_class_mtx_sleep,
 	    ("mtx_trylock() of spin mutex %s @ %s:%d", m->mtx_object.lo_name,
 	    file, line));
@@ -920,6 +930,7 @@
 		    __LINE__);
 	}
 
+	m->mtx_lock = MTX_DESTROYED;
 	lock_destroy(&m->mtx_object);
 }
 

==== //depot/projects/smpng/sys/modules/crash/crash.c#33 (text+ko) ====

@@ -87,6 +87,20 @@
 /* Events. */
 
 static void
+lock_destroyed_mtx(void)
+{
+
+	bzero(&test1_mtx, sizeof(test1_mtx));
+	mtx_init(&test1_mtx, "test1", NULL, MTX_DEF | MTX_RECURSE);
+	mtx_lock(&test1_mtx);
+	mtx_destroy(&test1_mtx);
+	kdb_enter("examine test1");
+	mtx_lock(&test1_mtx);
+	kdb_enter("examine again");
+}
+CRASH_EVENT("lock destroyed mutex", lock_destroyed_mtx);
+
+static void
 upgrade_baz(void)
 {
 	rw_init(&baz, "baz");

==== //depot/projects/smpng/sys/sys/mutex.h#64 (text+ko) ====

@@ -73,6 +73,11 @@
 #define MTX_UNOWNED	0x00000004	/* Cookie for free mutex */
 #define	MTX_FLAGMASK	(MTX_RECURSED | MTX_CONTESTED | MTX_UNOWNED)
 
+/*
+ * Value stored in mutex->mtx_lock to denote a destroyed mutex.
+ */
+#define	MTX_DESTROYED	(MTX_CONTESTED | MTX_UNOWNED)
+
 #endif	/* _KERNEL */
 
 #ifndef LOCORE