- Remove witness_dead and just use witness_watch instead. If witness_watch
is set to 0, it now has the same affect as setting witness_dead used to have. - Added a sysctl handler that allows root to change witness_watch from a non-zero value to zero to disable witness at runtime. Note that you can't turn witness back on once it is off. You can only turn it off as a one-way switch. - Added a comment describing the possible values of witness_watch.
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jhb
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@ -166,6 +166,7 @@ static int rebalancetree(struct witness_list *list);
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static void removechild(struct witness *parent, struct witness *child);
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static int reparentchildren(struct witness *newparent,
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struct witness *oldparent);
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static int sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS);
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static void witness_displaydescendants(void(*)(const char *fmt, ...),
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struct witness *, int indent);
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static const char *fixup_filename(const char *file);
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@ -189,9 +190,19 @@ static void witness_display(void(*)(const char *fmt, ...));
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MALLOC_DEFINE(M_WITNESS, "witness", "witness structure");
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/*
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* If set to 0, witness is disabled. If set to 1, witness performs full lock
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* order checking for all locks. If set to 2 or higher, then witness skips
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* the full lock order check if the lock being acquired is at a higher level
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* (i.e. farther down in the tree) than the current lock. This last mode is
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* somewhat experimental and not considered fully safe. At runtime, this
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* value may be set to 0 to turn off witness. witness is not allowed be
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* turned on once it is turned off, however.
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*/
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static int witness_watch = 1;
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TUNABLE_INT("debug.witness_watch", &witness_watch);
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SYSCTL_INT(_debug, OID_AUTO, witness_watch, CTLFLAG_RD, &witness_watch, 0, "");
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SYSCTL_PROC(_debug, OID_AUTO, witness_watch, CTLFLAG_RW | CTLTYPE_INT, NULL, 0,
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sysctl_debug_witness_watch, "I", "witness is watching lock operations");
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#ifdef DDB
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/*
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@ -235,7 +246,6 @@ static struct witness_list w_spin = STAILQ_HEAD_INITIALIZER(w_spin);
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static struct witness_list w_sleep = STAILQ_HEAD_INITIALIZER(w_sleep);
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static struct witness_child_list_entry *w_child_free = NULL;
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static struct lock_list_entry *w_lock_list_free = NULL;
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static int witness_dead; /* fatal error, probably no memory */
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static struct witness w_data[WITNESS_COUNT];
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static struct witness_child_list_entry w_childdata[WITNESS_CHILDCOUNT];
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@ -406,6 +416,26 @@ witness_initialize(void *dummy __unused)
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}
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SYSINIT(witness_init, SI_SUB_WITNESS, SI_ORDER_FIRST, witness_initialize, NULL)
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static int
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sysctl_debug_witness_watch(SYSCTL_HANDLER_ARGS)
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{
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int error, value;
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value = witness_watch;
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error = sysctl_handle_int(oidp, &value, 0, req);
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if (error != 0 || req->newptr == NULL)
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return (error);
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error = suser(req->td);
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if (error != 0)
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return (error);
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if (value == witness_watch)
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return (0);
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if (value != 0)
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return (EINVAL);
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witness_watch = 0;
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return (0);
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}
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void
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witness_init(struct lock_object *lock)
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{
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@ -435,7 +465,7 @@ witness_init(struct lock_object *lock)
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if (lock_cur_cnt > lock_max_cnt)
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lock_max_cnt = lock_cur_cnt;
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mtx_unlock(&all_mtx);
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if (!witness_cold && !witness_dead && panicstr == NULL &&
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if (!witness_cold && witness_watch != 0 && panicstr == NULL &&
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(lock->lo_flags & LO_WITNESS) != 0)
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lock->lo_witness = enroll(lock->lo_type, class);
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else
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@ -556,7 +586,7 @@ witness_lock(struct lock_object *lock, int flags, const char *file, int line)
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int go_into_ddb = 0;
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#endif
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if (witness_cold || witness_dead || lock->lo_witness == NULL ||
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if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
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panicstr != NULL)
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return;
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w = lock->lo_witness;
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@ -834,7 +864,7 @@ witness_upgrade(struct lock_object *lock, int flags, const char *file, int line)
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struct lock_class *class;
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KASSERT(!witness_cold, ("%s: witness_cold", __func__));
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if (lock->lo_witness == NULL || witness_dead || panicstr != NULL)
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if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
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return;
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class = lock->lo_class;
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file = fixup_filename(file);
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@ -869,7 +899,7 @@ witness_downgrade(struct lock_object *lock, int flags, const char *file,
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struct lock_class *class;
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KASSERT(!witness_cold, ("%s: witness_cold", __func__));
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if (lock->lo_witness == NULL || witness_dead || panicstr != NULL)
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if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
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return;
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class = lock->lo_class;
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file = fixup_filename(file);
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@ -903,7 +933,7 @@ witness_unlock(struct lock_object *lock, int flags, const char *file, int line)
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register_t s;
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int i, j;
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if (witness_cold || witness_dead || lock->lo_witness == NULL ||
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if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL ||
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panicstr != NULL)
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return;
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td = curthread;
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@ -993,7 +1023,7 @@ witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
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va_list ap;
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int i, n;
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if (witness_cold || witness_dead || panicstr != NULL)
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if (witness_cold || witness_watch == 0 || panicstr != NULL)
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return (0);
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n = 0;
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td = curthread;
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@ -1050,7 +1080,7 @@ witness_file(struct lock_object *lock)
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{
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struct witness *w;
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if (witness_cold || witness_dead || lock->lo_witness == NULL)
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if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL)
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return ("?");
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w = lock->lo_witness;
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return (w->w_file);
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@ -1061,7 +1091,7 @@ witness_line(struct lock_object *lock)
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{
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struct witness *w;
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if (witness_cold || witness_dead || lock->lo_witness == NULL)
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if (witness_cold || witness_watch == 0 || lock->lo_witness == NULL)
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return (0);
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w = lock->lo_witness;
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return (w->w_line);
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@ -1072,7 +1102,7 @@ enroll(const char *description, struct lock_class *lock_class)
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{
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struct witness *w;
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if (!witness_watch || witness_dead || panicstr != NULL)
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if (!witness_watch || witness_watch == 0 || panicstr != NULL)
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return (NULL);
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if ((lock_class->lc_flags & LC_SPINLOCK) && witness_skipspin)
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return (NULL);
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@ -1428,12 +1458,12 @@ witness_get(void)
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{
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struct witness *w;
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if (witness_dead) {
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if (witness_watch == 0) {
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mtx_unlock_spin(&w_mtx);
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return (NULL);
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}
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if (STAILQ_EMPTY(&w_free)) {
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witness_dead = 1;
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witness_watch = 0;
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mtx_unlock_spin(&w_mtx);
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printf("%s: witness exhausted\n", __func__);
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return (NULL);
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@ -1456,13 +1486,13 @@ witness_child_get(void)
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{
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struct witness_child_list_entry *wcl;
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if (witness_dead) {
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if (witness_watch == 0) {
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mtx_unlock_spin(&w_mtx);
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return (NULL);
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}
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wcl = w_child_free;
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if (wcl == NULL) {
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witness_dead = 1;
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witness_watch = 0;
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mtx_unlock_spin(&w_mtx);
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printf("%s: witness exhausted\n", __func__);
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return (NULL);
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@ -1485,12 +1515,12 @@ witness_lock_list_get(void)
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{
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struct lock_list_entry *lle;
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if (witness_dead)
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if (witness_watch == 0)
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return (NULL);
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mtx_lock_spin(&w_mtx);
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lle = w_lock_list_free;
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if (lle == NULL) {
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witness_dead = 1;
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witness_watch = 0;
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mtx_unlock_spin(&w_mtx);
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printf("%s: witness exhausted\n", __func__);
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return (NULL);
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@ -1563,7 +1593,7 @@ witness_save(struct lock_object *lock, const char **filep, int *linep)
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struct lock_instance *instance;
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KASSERT(!witness_cold, ("%s: witness_cold", __func__));
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if (lock->lo_witness == NULL || witness_dead || panicstr != NULL)
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if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
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return;
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if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0)
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panic("%s: lock (%s) %s is not a sleep lock", __func__,
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@ -1582,7 +1612,7 @@ witness_restore(struct lock_object *lock, const char *file, int line)
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struct lock_instance *instance;
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KASSERT(!witness_cold, ("%s: witness_cold", __func__));
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if (lock->lo_witness == NULL || witness_dead || panicstr != NULL)
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if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
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return;
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if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) == 0)
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panic("%s: lock (%s) %s is not a sleep lock", __func__,
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@ -1603,7 +1633,7 @@ witness_assert(struct lock_object *lock, int flags, const char *file, int line)
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#ifdef INVARIANT_SUPPORT
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struct lock_instance *instance;
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if (lock->lo_witness == NULL || witness_dead || panicstr != NULL)
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if (lock->lo_witness == NULL || witness_watch == 0 || panicstr != NULL)
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return;
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if ((lock->lo_class->lc_flags & LC_SLEEPLOCK) != 0)
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instance = find_instance(curthread->td_sleeplocks, lock);
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@ -1667,7 +1697,7 @@ witness_list(struct thread *td)
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KASSERT(!witness_cold, ("%s: witness_cold", __func__));
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KASSERT(db_active, ("%s: not in the debugger", __func__));
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if (witness_dead)
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if (witness_watch == 0)
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return;
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witness_list_locks(&td->td_sleeplocks);
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