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src/sys/kern/subr_witness.c

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/* $OpenBSD: subr_witness.c,v 1.54 2024/09/25 18:24:13 bluhm Exp $ */
/*-
* Copyright (c) 2008 Isilon Systems, Inc.
* Copyright (c) 2008 Ilya Maykov <ivmaykov@gmail.com>
* Copyright (c) 1998 Berkeley Software Design, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Berkeley Software Design Inc's name may not be used to endorse or
* promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from BSDI Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp
* and BSDI Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp
*/
/*
* Implementation of the `witness' lock verifier. Originally implemented for
* mutexes in BSD/OS. Extended to handle generic lock objects and lock
* classes in FreeBSD.
*/
/*
* Main Entry: witness
* Pronunciation: 'wit-n&s
* Function: noun
* Etymology: Middle English witnesse, from Old English witnes knowledge,
* testimony, witness, from 2wit
* Date: before 12th century
* 1 : attestation of a fact or event : TESTIMONY
* 2 : one that gives evidence; specifically : one who testifies in
* a cause or before a judicial tribunal
* 3 : one asked to be present at a transaction so as to be able to
* testify to its having taken place
* 4 : one who has personal knowledge of something
* 5 a : something serving as evidence or proof : SIGN
* b : public affirmation by word or example of usually
* religious faith or conviction <the heroic witness to divine
* life -- Pilot>
* 6 capitalized : a member of the Jehovah's Witnesses
*/
/*
* Special rules concerning Giant and lock orders:
*
* 1) Giant must be acquired before any other mutexes. Stated another way,
* no other mutex may be held when Giant is acquired.
*
* 2) Giant must be released when blocking on a sleepable lock.
*
* This rule is less obvious, but is a result of Giant providing the same
* semantics as spl(). Basically, when a thread sleeps, it must release
* Giant. When a thread blocks on a sleepable lock, it sleeps. Hence rule
* 2).
*
* 3) Giant may be acquired before or after sleepable locks.
*
* This rule is also not quite as obvious. Giant may be acquired after
* a sleepable lock because it is a non-sleepable lock and non-sleepable
* locks may always be acquired while holding a sleepable lock. The second
* case, Giant before a sleepable lock, follows from rule 2) above. Suppose
* you have two threads T1 and T2 and a sleepable lock X. Suppose that T1
* acquires X and blocks on Giant. Then suppose that T2 acquires Giant and
* blocks on X. When T2 blocks on X, T2 will release Giant allowing T1 to
* execute. Thus, acquiring Giant both before and after a sleepable lock
* will not result in a lock order reversal.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#ifdef MULTIPROCESSOR
#include <sys/mplock.h>
#endif
#include <sys/mutex.h>
#include <sys/percpu.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/stacktrace.h>
#include <sys/stdint.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/witness.h>
#include <machine/cpu.h>
#include <uvm/uvm_extern.h> /* uvm_pageboot_alloc */
#ifndef DDB
#error "DDB is required for WITNESS"
#endif
#include <machine/db_machdep.h>
#include <ddb/db_access.h>
#include <ddb/db_var.h>
#include <ddb/db_output.h>
#define LI_RECURSEMASK 0x0000ffff /* Recursion depth of lock instance. */
#define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */
#define LI_NORELEASE 0x00020000 /* Lock not allowed to be released. */
#ifndef WITNESS_COUNT
#define WITNESS_COUNT 1536
#endif
#define WITNESS_HASH_SIZE 251 /* Prime, gives load factor < 2 */
#define WITNESS_PENDLIST (1024 + MAXCPUS)
/* Allocate 256 KB of stack data space */
#define WITNESS_LO_DATA_COUNT 2048
/* Prime, gives load factor of ~2 at full load */
#define WITNESS_LO_HASH_SIZE 1021
/*
* XXX: This is somewhat bogus, as we assume here that at most 2048 threads
* will hold LOCK_NCHILDREN locks. We handle failure ok, and we should
* probably be safe for the most part, but it's still a SWAG.
*/
#define LOCK_NCHILDREN 5
#define LOCK_CHILDCOUNT 2048
#define FULLGRAPH_SBUF_SIZE 512
/*
* These flags go in the witness relationship matrix and describe the
* relationship between any two struct witness objects.
*/
#define WITNESS_UNRELATED 0x00 /* No lock order relation. */
#define WITNESS_PARENT 0x01 /* Parent, aka direct ancestor. */
#define WITNESS_ANCESTOR 0x02 /* Direct or indirect ancestor. */
#define WITNESS_CHILD 0x04 /* Child, aka direct descendant. */
#define WITNESS_DESCENDANT 0x08 /* Direct or indirect descendant. */
#define WITNESS_ANCESTOR_MASK (WITNESS_PARENT | WITNESS_ANCESTOR)
#define WITNESS_DESCENDANT_MASK (WITNESS_CHILD | WITNESS_DESCENDANT)
#define WITNESS_RELATED_MASK \
(WITNESS_ANCESTOR_MASK | WITNESS_DESCENDANT_MASK)
#define WITNESS_REVERSAL 0x10 /* A lock order reversal has been
* observed. */
#define WITNESS_RESERVED1 0x20 /* Unused flag, reserved. */
#define WITNESS_RESERVED2 0x40 /* Unused flag, reserved. */
#define WITNESS_LOCK_ORDER_KNOWN 0x80 /* This lock order is known. */
/* Descendant to ancestor flags */
#define WITNESS_DTOA(x) (((x) & WITNESS_RELATED_MASK) >> 2)
/* Ancestor to descendant flags */
#define WITNESS_ATOD(x) (((x) & WITNESS_RELATED_MASK) << 2)
#define WITNESS_INDEX_ASSERT(i) \
KASSERT((i) > 0 && (i) <= w_max_used_index && (i) < witness_count)
/*
* Lock classes. Each lock has a class which describes characteristics
* common to all types of locks of a given class.
*
* Spin locks in general must always protect against preemption, as it is
* 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.
*/
struct lock_class {
const char *lc_name;
u_int lc_flags;
};
union lock_stack {
union lock_stack *ls_next;
struct stacktrace ls_stack;
};
#define LC_SLEEPLOCK 0x00000001 /* Sleep lock. */
#define LC_SPINLOCK 0x00000002 /* Spin lock. */
#define LC_SLEEPABLE 0x00000004 /* Sleeping allowed with this lock. */
#define LC_RECURSABLE 0x00000008 /* Locks of this type may recurse. */
#define LC_UPGRADABLE 0x00000010 /* Upgrades and downgrades permitted. */
/*
* Lock instances. A lock instance is the data associated with a lock while
* it is held by witness. For example, a lock instance will hold the
* recursion count of a lock. Lock instances are held in lists. Spin locks
* are held in a per-cpu list while sleep locks are held in per-thread list.
*/
struct lock_instance {
struct lock_object *li_lock;
union lock_stack *li_stack;
u_int li_flags;
};
/*
* A simple list type used to build the list of locks held by a thread
* or CPU. We can't simply embed the list in struct lock_object since a
* lock may be held by more than one thread if it is a shared lock. Locks
* are added to the head of the list, so we fill up each list entry from
* "the back" logically. To ease some of the arithmetic, we actually fill
* in each list entry the normal way (children[0] then children[1], etc.) but
* when we traverse the list we read children[count-1] as the first entry
* down to children[0] as the final entry.
*/
struct lock_list_entry {
struct lock_list_entry *ll_next;
struct lock_instance ll_children[LOCK_NCHILDREN];
int ll_count;
};
/*
* The main witness structure. One of these per named lock type in the system
* (for example, "vnode interlock").
*/
struct witness {
const struct lock_type *w_type;
const char *w_subtype;
uint32_t w_index; /* Index in the relationship matrix */
struct lock_class *w_class;
SLIST_ENTRY(witness) w_list; /* List of all witnesses. */
SLIST_ENTRY(witness) w_typelist; /* Witnesses of a type. */
SLIST_ENTRY(witness) w_hash_next; /* Linked list in
* hash buckets. */
uint16_t w_num_ancestors; /* direct/indirect
* ancestor count */
uint16_t w_num_descendants; /* direct/indirect
* descendant count */
int16_t w_ddb_level;
unsigned w_acquired:1;
unsigned w_displayed:1;
unsigned w_reversed:1;
};
SLIST_HEAD(witness_list, witness);
/*
* The witness hash table. Keys are witness names (const char *), elements are
* witness objects (struct witness *).
*/
struct witness_hash {
struct witness_list wh_array[WITNESS_HASH_SIZE];
uint32_t wh_size;
uint32_t wh_count;
};
/*
* Key type for the lock order data hash table.
*/
struct witness_lock_order_key {
uint16_t from;
uint16_t to;
};
struct witness_lock_order_data {
struct stacktrace wlod_stack;
struct witness_lock_order_key wlod_key;
struct witness_lock_order_data *wlod_next;
};
/*
* The witness lock order data hash table. Keys are witness index tuples
* (struct witness_lock_order_key), elements are lock order data objects
* (struct witness_lock_order_data).
*/
struct witness_lock_order_hash {
struct witness_lock_order_data *wloh_array[WITNESS_LO_HASH_SIZE];
u_int wloh_size;
u_int wloh_count;
};
struct witness_pendhelp {
const struct lock_type *wh_type;
struct lock_object *wh_lock;
};
struct witness_cpu {
struct lock_list_entry *wc_spinlocks;
struct lock_list_entry *wc_lle_cache;
union lock_stack *wc_stk_cache;
unsigned int wc_lle_count;
unsigned int wc_stk_count;
} __aligned(CACHELINESIZE);
#define WITNESS_LLE_CACHE_MAX 8
#define WITNESS_STK_CACHE_MAX (WITNESS_LLE_CACHE_MAX * LOCK_NCHILDREN)
struct witness_cpu witness_cpu[MAXCPUS];
/*
* Returns 0 if one of the locks is a spin lock and the other is not.
* Returns 1 otherwise.
*/
static __inline int
witness_lock_type_equal(struct witness *w1, struct witness *w2)
{
return ((w1->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)) ==
(w2->w_class->lc_flags & (LC_SLEEPLOCK | LC_SPINLOCK)));
}
static __inline int
witness_lock_order_key_equal(const struct witness_lock_order_key *a,
const struct witness_lock_order_key *b)
{
return (a->from == b->from && a->to == b->to);
}
static int _isitmyx(struct witness *w1, struct witness *w2, int rmask,
const char *fname);
static void adopt(struct witness *parent, struct witness *child);
static struct witness *enroll(const struct lock_type *, const char *,
struct lock_class *);
static struct lock_instance *find_instance(struct lock_list_entry *list,
const struct lock_object *lock);
static int isitmychild(struct witness *parent, struct witness *child);
static int isitmydescendant(struct witness *parent, struct witness *child);
static void itismychild(struct witness *parent, struct witness *child);
#ifdef DDB
static void db_witness_add_fullgraph(struct witness *parent);
static void witness_ddb_compute_levels(void);
static void witness_ddb_display(int(*)(const char *fmt, ...));
static void witness_ddb_display_descendants(int(*)(const char *fmt, ...),
struct witness *, int indent);
static void witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
struct witness_list *list);
static void witness_ddb_level_descendants(struct witness *parent, int l);
static void witness_ddb_list(struct proc *td);
#endif
static int witness_alloc_stacks(void);
static void witness_debugger(int dump);
static void witness_free(struct witness *m);
static struct witness *witness_get(void);
static uint32_t witness_hash_djb2(const uint8_t *key, uint32_t size);
static struct witness *witness_hash_get(const struct lock_type *,
const char *);
static void witness_hash_put(struct witness *w);
static void witness_init_hash_tables(void);
static void witness_increment_graph_generation(void);
static int witness_list_locks(struct lock_list_entry **,
int (*)(const char *, ...));
static void witness_lock_list_free(struct lock_list_entry *lle);
static struct lock_list_entry *witness_lock_list_get(void);
static void witness_lock_stack_free(union lock_stack *stack);
static union lock_stack *witness_lock_stack_get(void);
static int witness_lock_order_add(struct witness *parent,
struct witness *child);
static int witness_lock_order_check(struct witness *parent,
struct witness *child);
static struct witness_lock_order_data *witness_lock_order_get(
struct witness *parent,
struct witness *child);
static void witness_list_lock(struct lock_instance *instance,
int (*prnt)(const char *fmt, ...));
static void witness_print_cycle(int (*prnt)(const char *fmt, ...),
struct witness *parent, struct witness *child);
static void witness_print_cycle_edge(int (*prnt)(const char *fmt, ...),
struct witness *parent, struct witness *child,
int step, int last);
static int witness_search(struct witness *w, struct witness *target,
struct witness **path, int depth, int *remaining);
static void witness_setflag(struct lock_object *lock, int flag, int set);
/*
* If set to 0, lock order checking is disabled. If set to -1,
* witness is completely disabled. Otherwise witness performs full
* lock order checking for all locks. At runtime, lock order checking
* may be toggled. However, witness cannot be reenabled once it is
* completely disabled.
*/
#ifdef WITNESS_WATCH
static int witness_watch = 3;
#else
static int witness_watch = 2;
#endif
#ifdef WITNESS_LOCKTRACE
static int witness_locktrace = 1;
#else
static int witness_locktrace = 0;
#endif
int witness_count = WITNESS_COUNT;
int witness_uninitialized_report = 5;
static struct mutex w_mtx;
static struct rwlock w_ctlock = RWLOCK_INITIALIZER("w_ctlock");
/* w_list */
static struct witness_list w_free = SLIST_HEAD_INITIALIZER(w_free);
static struct witness_list w_all = SLIST_HEAD_INITIALIZER(w_all);
/* w_typelist */
static struct witness_list w_spin = SLIST_HEAD_INITIALIZER(w_spin);
static struct witness_list w_sleep = SLIST_HEAD_INITIALIZER(w_sleep);
/* lock list */
static struct lock_list_entry *w_lock_list_free = NULL;
static struct witness_pendhelp pending_locks[WITNESS_PENDLIST];
static u_int pending_cnt;
static int w_free_cnt, w_spin_cnt, w_sleep_cnt;
static struct witness *w_data;
static uint8_t **w_rmatrix;
static struct lock_list_entry *w_locklistdata;
static struct witness_hash w_hash; /* The witness hash table. */
/* The lock order data hash */
static struct witness_lock_order_data *w_lodata;
static struct witness_lock_order_data *w_lofree = NULL;
static struct witness_lock_order_hash w_lohash;
static int w_max_used_index = 0;
static unsigned int w_generation = 0;
static union lock_stack *w_lock_stack_free;
static unsigned int w_lock_stack_num;
static struct lock_class lock_class_kernel_lock = {
.lc_name = "kernel_lock",
.lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_SLEEPABLE
};
static struct lock_class lock_class_mutex = {
.lc_name = "mutex",
.lc_flags = LC_SPINLOCK
};
static struct lock_class lock_class_rwlock = {
.lc_name = "rwlock",
.lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_UPGRADABLE
};
static struct lock_class lock_class_rrwlock = {
.lc_name = "rrwlock",
.lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_SLEEPABLE |
LC_UPGRADABLE
};
static struct lock_class *lock_classes[] = {
&lock_class_kernel_lock,
&lock_class_mutex,
&lock_class_rwlock,
&lock_class_rrwlock,
};
/*
* This global is set to 0 once it becomes safe to use the witness code.
*/
static int witness_cold = 1;
/*
* This global is set to 1 once the static lock orders have been enrolled
* so that a warning can be issued for any spin locks enrolled later.
*/
static int witness_spin_warn = 0;
/*
* The WITNESS-enabled diagnostic code. Note that the witness code does
* assume that the early boot is single-threaded at least until after this
* routine is completed.
*/
void
witness_initialize(void)
{
struct lock_object *lock;
union lock_stack *stacks;
struct witness *w;
int i, s;
w_data = (void *)uvm_pageboot_alloc(sizeof(struct witness) *
witness_count);
memset(w_data, 0, sizeof(struct witness) * witness_count);
w_rmatrix = (void *)uvm_pageboot_alloc(sizeof(*w_rmatrix) *
(witness_count + 1));
for (i = 0; i < witness_count + 1; i++) {
w_rmatrix[i] = (void *)uvm_pageboot_alloc(
sizeof(*w_rmatrix[i]) * (witness_count + 1));
memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) *
(witness_count + 1));
}
mtx_init_flags(&w_mtx, IPL_HIGH, "witness lock", MTX_NOWITNESS);
for (i = witness_count - 1; i >= 0; i--) {
w = &w_data[i];
memset(w, 0, sizeof(*w));
w_data[i].w_index = i; /* Witness index never changes. */
witness_free(w);
}
KASSERTMSG(SLIST_FIRST(&w_free)->w_index == 0,
"%s: Invalid list of free witness objects", __func__);
/* Witness with index 0 is not used to aid in debugging. */
SLIST_REMOVE_HEAD(&w_free, w_list);
w_free_cnt--;
for (i = 0; i < witness_count; i++) {
memset(w_rmatrix[i], 0, sizeof(*w_rmatrix[i]) *
(witness_count + 1));
}
if (witness_locktrace) {
w_lock_stack_num = LOCK_CHILDCOUNT * LOCK_NCHILDREN;
stacks = (void *)uvm_pageboot_alloc(sizeof(*stacks) *
w_lock_stack_num);
}
w_locklistdata = (void *)uvm_pageboot_alloc(
sizeof(struct lock_list_entry) * LOCK_CHILDCOUNT);
memset(w_locklistdata, 0, sizeof(struct lock_list_entry) *
LOCK_CHILDCOUNT);
s = splhigh();
for (i = 0; i < w_lock_stack_num; i++)
witness_lock_stack_free(&stacks[i]);
for (i = 0; i < LOCK_CHILDCOUNT; i++)
witness_lock_list_free(&w_locklistdata[i]);
splx(s);
witness_init_hash_tables();
witness_spin_warn = 1;
/* Iterate through all locks and add them to witness. */
for (i = 0; pending_locks[i].wh_lock != NULL; i++) {
lock = pending_locks[i].wh_lock;
KASSERTMSG(lock->lo_flags & LO_WITNESS,
"%s: lock %s is on pending list but not LO_WITNESS",
__func__, lock->lo_name);
lock->lo_witness = enroll(pending_locks[i].wh_type,
lock->lo_name, LOCK_CLASS(lock));
}
/* Mark the witness code as being ready for use. */
witness_cold = 0;
}
void
witness_init(struct lock_object *lock, const struct lock_type *type)
{
struct lock_class *class;
/* Various sanity checks. */
class = LOCK_CLASS(lock);
if ((lock->lo_flags & LO_RECURSABLE) != 0 &&
(class->lc_flags & LC_RECURSABLE) == 0)
panic("%s: lock (%s) %s can not be recursable",
__func__, class->lc_name, lock->lo_name);
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(class->lc_flags & LC_SLEEPABLE) == 0)
panic("%s: lock (%s) %s can not be sleepable",
__func__, class->lc_name, lock->lo_name);
if ((lock->lo_flags & LO_UPGRADABLE) != 0 &&
(class->lc_flags & LC_UPGRADABLE) == 0)
panic("%s: lock (%s) %s can not be upgradable",
__func__, class->lc_name, lock->lo_name);
/*
* If we shouldn't watch this lock, then just clear lo_witness.
* Record the type in case the lock becomes watched later.
* Otherwise, if witness_cold is set, then it is too early to
* enroll this lock, so defer it to witness_initialize() by adding
* it to the pending_locks list. If it is not too early, then enroll
* the lock now.
*/
if (witness_watch < 1 || panicstr != NULL || db_active ||
(lock->lo_flags & LO_WITNESS) == 0) {
lock->lo_witness = NULL;
lock->lo_type = type;
} else if (witness_cold) {
pending_locks[pending_cnt].wh_lock = lock;
pending_locks[pending_cnt++].wh_type = type;
if (pending_cnt > WITNESS_PENDLIST)
panic("%s: pending locks list is too small, "
"increase WITNESS_PENDLIST",
__func__);
} else
lock->lo_witness = enroll(type, lock->lo_name, class);
}
static inline int
is_kernel_lock(const struct lock_object *lock)
{
#ifdef MULTIPROCESSOR
return (lock == &kernel_lock.mpl_lock_obj);
#else
return (0);
#endif
}
#ifdef DDB
static void
witness_ddb_compute_levels(void)
{
struct witness *w;
/*
* First clear all levels.
*/
SLIST_FOREACH(w, &w_all, w_list)
w->w_ddb_level = -1;
/*
* Look for locks with no parents and level all their descendants.
*/
SLIST_FOREACH(w, &w_all, w_list) {
/* If the witness has ancestors (is not a root), skip it. */
if (w->w_num_ancestors > 0)
continue;
witness_ddb_level_descendants(w, 0);
}
}
static void
witness_ddb_level_descendants(struct witness *w, int l)
{
int i;
if (w->w_ddb_level >= l)
return;
w->w_ddb_level = l;
l++;
for (i = 1; i <= w_max_used_index; i++) {
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
witness_ddb_level_descendants(&w_data[i], l);
}
}
static void
witness_ddb_display_descendants(int(*prnt)(const char *fmt, ...),
struct witness *w, int indent)
{
int i;
for (i = 0; i < indent; i++)
prnt(" ");
prnt("%s (%s) (type: %s, depth: %d)",
w->w_subtype, w->w_type->lt_name,
w->w_class->lc_name, w->w_ddb_level);
if (w->w_displayed) {
prnt(" -- (already displayed)\n");
return;
}
w->w_displayed = 1;
if (!w->w_acquired)
prnt(" -- never acquired\n");
else
prnt("\n");
indent++;
WITNESS_INDEX_ASSERT(w->w_index);
for (i = 1; i <= w_max_used_index; i++) {
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT)
witness_ddb_display_descendants(prnt, &w_data[i],
indent);
}
}
static void
witness_ddb_display_list(int(*prnt)(const char *fmt, ...),
struct witness_list *list)
{
struct witness *w;
SLIST_FOREACH(w, list, w_typelist) {
if (!w->w_acquired || w->w_ddb_level > 0)
continue;
/* This lock has no ancestors - display its descendants. */
witness_ddb_display_descendants(prnt, w, 0);
}
}
static void
witness_ddb_display(int(*prnt)(const char *fmt, ...))
{
struct witness *w;
KASSERTMSG(witness_cold == 0, "%s: witness_cold", __func__);
witness_ddb_compute_levels();
/* Clear all the displayed flags. */
SLIST_FOREACH(w, &w_all, w_list)
w->w_displayed = 0;
/*
* First, handle sleep locks which have been acquired at least
* once.
*/
prnt("Sleep locks:\n");
witness_ddb_display_list(prnt, &w_sleep);
/*
* Now do spin locks which have been acquired at least once.
*/
prnt("\nSpin locks:\n");
witness_ddb_display_list(prnt, &w_spin);
/*
* Finally, any locks which have not been acquired yet.
*/
prnt("\nLocks which were never acquired:\n");
SLIST_FOREACH(w, &w_all, w_list) {
if (w->w_acquired)
continue;
prnt("%s (%s) (type: %s, depth: %d)\n",
w->w_subtype, w->w_type->lt_name,
w->w_class->lc_name, w->w_ddb_level);
}
}
#endif /* DDB */
int
witness_defineorder(struct lock_object *lock1, struct lock_object *lock2)
{
if (witness_watch < 0 || panicstr != NULL || db_active)
return (0);
/* Require locks that witness knows about. */
if (lock1 == NULL || lock1->lo_witness == NULL || lock2 == NULL ||
lock2->lo_witness == NULL)
return (EINVAL);
MUTEX_ASSERT_UNLOCKED(&w_mtx);
mtx_enter(&w_mtx);
/*
* If we already have either an explicit or implied lock order that
* is the other way around, then return an error.
*/
if (witness_watch &&
isitmydescendant(lock2->lo_witness, lock1->lo_witness)) {
mtx_leave(&w_mtx);
return (EINVAL);
}
/* Try to add the new order. */
itismychild(lock1->lo_witness, lock2->lo_witness);
mtx_leave(&w_mtx);
return (0);
}
void
witness_checkorder(struct lock_object *lock, int flags,
struct lock_object *interlock)
{
struct lock_list_entry *lock_list, *lle;
struct lock_instance *lock1, *lock2, *plock;
struct lock_class *class, *iclass;
struct witness *w, *w1;
int i, j, s;
if (witness_cold || witness_watch < 1 || panicstr != NULL || db_active)
return;
if ((lock->lo_flags & LO_INITIALIZED) == 0) {
if (witness_uninitialized_report > 0) {
witness_uninitialized_report--;
printf("witness: lock_object uninitialized: %p\n", lock);
witness_debugger(1);
}
lock->lo_flags |= LO_INITIALIZED;
}
if ((lock->lo_flags & LO_WITNESS) == 0)
return;
w = lock->lo_witness;
class = LOCK_CLASS(lock);
if (w == NULL)
w = lock->lo_witness =
enroll(lock->lo_type, lock->lo_name, class);
if (class->lc_flags & LC_SLEEPLOCK) {
struct proc *p;
/*
* Since spin locks include a critical section, this check
* implicitly enforces a lock order of all sleep locks before
* all spin locks.
*/
lock_list = witness_cpu[cpu_number()].wc_spinlocks;
if (lock_list != NULL && lock_list->ll_count > 0) {
panic("acquiring blockable sleep lock with "
"spinlock or critical section held (%s) %s",
class->lc_name, lock->lo_name);
}
/*
* If this is the first lock acquired then just return as
* no order checking is needed.
*/
p = curproc;
if (p == NULL)
return;
lock_list = p->p_sleeplocks;
if (lock_list == NULL || lock_list->ll_count == 0)
return;
} else {
/*
* If this is the first lock, just return as no order
* checking is needed.
*/
lock_list = witness_cpu[cpu_number()].wc_spinlocks;
if (lock_list == NULL || lock_list->ll_count == 0)
return;
}
s = splhigh();
/*
* Check to see if we are recursing on a lock we already own. If
* so, make sure that we don't mismatch exclusive and shared lock
* acquires.
*/
lock1 = find_instance(lock_list, lock);
if (lock1 != NULL) {
if ((lock1->li_flags & LI_EXCLUSIVE) != 0 &&
(flags & LOP_EXCLUSIVE) == 0) {
printf("witness: shared lock of (%s) %s "
"while exclusively locked\n",
class->lc_name, lock->lo_name);
panic("excl->share");
}
if ((lock1->li_flags & LI_EXCLUSIVE) == 0 &&
(flags & LOP_EXCLUSIVE) != 0) {
printf("witness: exclusive lock of (%s) %s "
"while share locked\n",
class->lc_name, lock->lo_name);
panic("share->excl");
}
goto out_splx;
}
/* Warn if the interlock is not locked exactly once. */
if (interlock != NULL) {
iclass = LOCK_CLASS(interlock);
lock1 = find_instance(lock_list, interlock);
if (lock1 == NULL)
panic("interlock (%s) %s not locked",
iclass->lc_name, interlock->lo_name);
else if ((lock1->li_flags & LI_RECURSEMASK) != 0)
panic("interlock (%s) %s recursed",
iclass->lc_name, interlock->lo_name);
}
/*
* Find the previously acquired lock, but ignore interlocks.
*/
plock = &lock_list->ll_children[lock_list->ll_count - 1];
if (interlock != NULL && plock->li_lock == interlock) {
if (lock_list->ll_count > 1)
plock =
&lock_list->ll_children[lock_list->ll_count - 2];
else {
lle = lock_list->ll_next;
/*
* The interlock is the only lock we hold, so
* simply return.
*/
if (lle == NULL)
goto out_splx;
plock = &lle->ll_children[lle->ll_count - 1];
}
}
/*
* Try to perform most checks without a lock. If this succeeds we
* can skip acquiring the lock and return success. Otherwise we redo
* the check with the lock held to handle races with concurrent updates.
*/
w1 = plock->li_lock->lo_witness;
if (witness_lock_order_check(w1, w))
goto out_splx;
mtx_enter(&w_mtx);
if (witness_lock_order_check(w1, w))
goto out;
witness_lock_order_add(w1, w);
/*
* Check for duplicate locks of the same type. Note that we only
* have to check for this on the last lock we just acquired. Any
* other cases will be caught as lock order violations.
*/
if (w1 == w) {
i = w->w_index;
if (!(lock->lo_flags & LO_DUPOK) && !(flags & LOP_DUPOK) &&
!(w_rmatrix[i][i] & WITNESS_REVERSAL)) {
w_rmatrix[i][i] |= WITNESS_REVERSAL;
w->w_reversed = 1;
mtx_leave(&w_mtx);
printf("witness: acquiring duplicate lock of "
"same type: \"%s\"\n", w->w_type->lt_name);
printf(" 1st %s\n", plock->li_lock->lo_name);
printf(" 2nd %s\n", lock->lo_name);
witness_debugger(1);
} else
mtx_leave(&w_mtx);
goto out_splx;
}
MUTEX_ASSERT_LOCKED(&w_mtx);
/*
* If we know that the lock we are acquiring comes after
* the lock we most recently acquired in the lock order tree,
* then there is no need for any further checks.
*/
if (isitmychild(w1, w))
goto out;
for (j = 0, lle = lock_list; lle != NULL; lle = lle->ll_next) {
for (i = lle->ll_count - 1; i >= 0; i--, j++) {
KASSERT(j < LOCK_CHILDCOUNT * LOCK_NCHILDREN);
lock1 = &lle->ll_children[i];
/*
* Ignore the interlock.
*/
if (interlock == lock1->li_lock)
continue;
/*
* If this lock doesn't undergo witness checking,
* then skip it.
*/
w1 = lock1->li_lock->lo_witness;
if (w1 == NULL) {
KASSERTMSG((lock1->li_lock->lo_flags &
LO_WITNESS) == 0,
"lock missing witness structure");
continue;
}
/*
* If we are locking Giant and this is a sleepable
* lock, then skip it.
*/
if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
is_kernel_lock(lock))
continue;
/*
* If we are locking a sleepable lock and this lock
* is Giant, then skip it.
*/
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
is_kernel_lock(lock1->li_lock))
continue;
/*
* If we are locking a sleepable lock and this lock
* isn't sleepable, we want to treat it as a lock
* order violation to enforce a general lock order of
* sleepable locks before non-sleepable locks.
*/
if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
goto reversal;
/*
* If we are locking Giant and this is a non-sleepable
* lock, then treat it as a reversal.
*/
if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
is_kernel_lock(lock))
goto reversal;
/*
* Check the lock order hierarchy for a reveresal.
*/
if (!isitmydescendant(w, w1))
continue;
reversal:
/*
* We have a lock order violation, check to see if it
* is allowed or has already been yelled about.
*/
/* Bail if this violation is known */
if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
goto out;
/* Record this as a violation */
w_rmatrix[w1->w_index][w->w_index] |= WITNESS_REVERSAL;
w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL;
w->w_reversed = w1->w_reversed = 1;
witness_increment_graph_generation();
mtx_leave(&w_mtx);
/*
* There are known LORs between VNODE locks. They are
* not an indication of a bug. VNODE locks are flagged
* as such (LO_IS_VNODE) and we don't yell if the LOR
* is between 2 VNODE locks.
*/
if ((lock->lo_flags & LO_IS_VNODE) != 0 &&
(lock1->li_lock->lo_flags & LO_IS_VNODE) != 0)
goto out_splx;
/*
* Ok, yell about it.
*/
printf("witness: ");
if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
(lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
printf("lock order reversal: "
"(sleepable after non-sleepable)\n");
else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
&& is_kernel_lock(lock))
printf("lock order reversal: "
"(Giant after non-sleepable)\n");
else
printf("lock order reversal:\n");
/*
* Try to locate an earlier lock with
* witness w in our list.
*/
do {
lock2 = &lle->ll_children[i];
KASSERT(lock2->li_lock != NULL);
if (lock2->li_lock->lo_witness == w)
break;
if (i == 0 && lle->ll_next != NULL) {
lle = lle->ll_next;
i = lle->ll_count - 1;
KASSERT(i >= 0 && i < LOCK_NCHILDREN);
} else
i--;
} while (i >= 0);
if (i < 0) {
printf(" 1st %p %s (%s)\n",
lock1->li_lock, lock1->li_lock->lo_name,
w1->w_type->lt_name);
printf(" 2nd %p %s (%s)\n",
lock, lock->lo_name, w->w_type->lt_name);
} else {
printf(" 1st %p %s (%s)\n",
lock2->li_lock, lock2->li_lock->lo_name,
lock2->li_lock->lo_witness->w_type->
lt_name);
printf(" 2nd %p %s (%s)\n",
lock1->li_lock, lock1->li_lock->lo_name,
w1->w_type->lt_name);
printf(" 3rd %p %s (%s)\n", lock,
lock->lo_name, w->w_type->lt_name);
}
if (witness_watch > 1)
witness_print_cycle(printf, w1, w);
witness_debugger(0);
goto out_splx;
}
}
/*
* If requested, build a new lock order. However, don't build a new
* relationship between a sleepable lock and Giant if it is in the
* wrong direction. The correct lock order is that sleepable locks
* always come before Giant.
*/
if (flags & LOP_NEWORDER &&
!(is_kernel_lock(plock->li_lock) &&
(lock->lo_flags & LO_SLEEPABLE) != 0))
itismychild(plock->li_lock->lo_witness, w);
out:
mtx_leave(&w_mtx);
out_splx:
splx(s);
}
void
witness_lock(struct lock_object *lock, int flags)
{
struct lock_list_entry **lock_list, *lle;
struct lock_instance *instance;
struct witness *w;
int s;
if (witness_cold || witness_watch < 0 || panicstr != NULL ||
db_active || (lock->lo_flags & LO_WITNESS) == 0)
return;
w = lock->lo_witness;
if (w == NULL)
w = lock->lo_witness =
enroll(lock->lo_type, lock->lo_name, LOCK_CLASS(lock));
/* Determine lock list for this lock. */
if (LOCK_CLASS(lock)->lc_flags & LC_SLEEPLOCK) {
struct proc *p;
p = curproc;
if (p == NULL)
return;
lock_list = &p->p_sleeplocks;
} else
lock_list = &witness_cpu[cpu_number()].wc_spinlocks;
s = splhigh();
/* Check to see if we are recursing on a lock we already own. */
instance = find_instance(*lock_list, lock);
if (instance != NULL) {
instance->li_flags++;
goto out;
}
w->w_acquired = 1;
/* Find the next open lock instance in the list and fill it. */
lle = *lock_list;
if (lle == NULL || lle->ll_count == LOCK_NCHILDREN) {
lle = witness_lock_list_get();
if (lle == NULL)
goto out;
lle->ll_next = *lock_list;
*lock_list = lle;
}
instance = &lle->ll_children[lle->ll_count++];
instance->li_lock = lock;
if ((flags & LOP_EXCLUSIVE) != 0)
instance->li_flags = LI_EXCLUSIVE;
else
instance->li_flags = 0;
instance->li_stack = NULL;
if (witness_locktrace) {
instance->li_stack = witness_lock_stack_get();
if (instance->li_stack != NULL)
stacktrace_save(&instance->li_stack->ls_stack);
}
out:
splx(s);
}
void
witness_upgrade(struct lock_object *lock, int flags)
{
struct lock_instance *instance;
struct lock_class *class;
int s;
KASSERTMSG(witness_cold == 0, "%s: witness_cold", __func__);
if (lock->lo_witness == NULL || witness_watch < 0 ||
panicstr != NULL || db_active)
return;
class = LOCK_CLASS(lock);
if (witness_watch) {
if ((lock->lo_flags & LO_UPGRADABLE) == 0)
panic("upgrade of non-upgradable lock (%s) %s",
class->lc_name, lock->lo_name);
if ((class->lc_flags & LC_SLEEPLOCK) == 0)
panic("upgrade of non-sleep lock (%s) %s",
class->lc_name, lock->lo_name);
}
s = splhigh();
instance = find_instance(curproc->p_sleeplocks, lock);
if (instance == NULL) {
panic("upgrade of unlocked lock (%s) %s",
class->lc_name, lock->lo_name);
goto out;
}
if (witness_watch) {
if ((instance->li_flags & LI_EXCLUSIVE) != 0)
panic("upgrade of exclusive lock (%s) %s",
class->lc_name, lock->lo_name);
if ((instance->li_flags & LI_RECURSEMASK) != 0)
panic("upgrade of recursed lock (%s) %s r=%d",
class->lc_name, lock->lo_name,
instance->li_flags & LI_RECURSEMASK);
}
instance->li_flags |= LI_EXCLUSIVE;
out:
splx(s);
}
void
witness_downgrade(struct lock_object *lock, int flags)
{
struct lock_instance *instance;
struct lock_class *class;
int s;
KASSERTMSG(witness_cold == 0, "%s: witness_cold", __func__);
if (lock->lo_witness == NULL || witness_watch < 0 ||
panicstr != NULL || db_active)
return;
class = LOCK_CLASS(lock);
if (witness_watch) {
if ((lock->lo_flags & LO_UPGRADABLE) == 0)
panic(
"downgrade of non-upgradable lock (%s) %s",
class->lc_name, lock->lo_name);
if ((class->lc_flags & LC_SLEEPLOCK) == 0)
panic("downgrade of non-sleep lock (%s) %s",
class->lc_name, lock->lo_name);
}
s = splhigh();
instance = find_instance(curproc->p_sleeplocks, lock);
if (instance == NULL) {
panic("downgrade of unlocked lock (%s) %s",
class->lc_name, lock->lo_name);
goto out;
}
if (witness_watch) {
if ((instance->li_flags & LI_EXCLUSIVE) == 0)
panic("downgrade of shared lock (%s) %s",
class->lc_name, lock->lo_name);
if ((instance->li_flags & LI_RECURSEMASK) != 0)
panic("downgrade of recursed lock (%s) %s r=%d",
class->lc_name, lock->lo_name,
instance->li_flags & LI_RECURSEMASK);
}
instance->li_flags &= ~LI_EXCLUSIVE;
out:
splx(s);
}
void
witness_unlock(struct lock_object *lock, int flags)
{
struct lock_list_entry **lock_list, *lle;
struct lock_instance *instance;
struct lock_class *class;
int i, j;
int s;
if (witness_cold || lock->lo_witness == NULL ||
panicstr != NULL || db_active)
return;
class = LOCK_CLASS(lock);
/* Find lock instance associated with this lock. */
if (class->lc_flags & LC_SLEEPLOCK) {
struct proc *p;
p = curproc;
if (p == NULL)
return;
lock_list = &p->p_sleeplocks;
} else
lock_list = &witness_cpu[cpu_number()].wc_spinlocks;
s = splhigh();
lle = *lock_list;
for (; *lock_list != NULL; lock_list = &(*lock_list)->ll_next)
for (i = 0; i < (*lock_list)->ll_count; i++) {
instance = &(*lock_list)->ll_children[i];
if (instance->li_lock == lock)
goto found;
}
/*
* When disabling WITNESS through witness_watch we could end up in
* having registered locks in the p_sleeplocks queue.
* We have to make sure we flush these queues, so just search for
* eventual register locks and remove them.
*/
if (witness_watch > 0) {
panic("lock (%s) %s not locked", class->lc_name, lock->lo_name);
}
goto out;
found:
/* First, check for shared/exclusive mismatches. */
if ((instance->li_flags & LI_EXCLUSIVE) != 0 && witness_watch > 0 &&
(flags & LOP_EXCLUSIVE) == 0) {
printf("witness: shared unlock of (%s) %s "
"while exclusively locked\n",
class->lc_name, lock->lo_name);
panic("excl->ushare");
}
if ((instance->li_flags & LI_EXCLUSIVE) == 0 && witness_watch > 0 &&
(flags & LOP_EXCLUSIVE) != 0) {
printf("witness: exclusive unlock of (%s) %s "
"while share locked\n", class->lc_name, lock->lo_name);
panic("share->uexcl");
}
/* If we are recursed, unrecurse. */
if ((instance->li_flags & LI_RECURSEMASK) > 0) {
instance->li_flags--;
goto out;
}
/* The lock is now being dropped, check for NORELEASE flag */
if ((instance->li_flags & LI_NORELEASE) != 0 && witness_watch > 0) {
printf("witness: forbidden unlock of (%s) %s\n",
class->lc_name, lock->lo_name);
panic("lock marked norelease");
}
/* Release the stack buffer, if any. */
if (instance->li_stack != NULL) {
witness_lock_stack_free(instance->li_stack);
instance->li_stack = NULL;
}
/* Remove this item from the list. */
for (j = i; j < (*lock_list)->ll_count - 1; j++)
(*lock_list)->ll_children[j] =
(*lock_list)->ll_children[j + 1];
(*lock_list)->ll_count--;
/*
* In order to reduce contention on w_mtx, we want to keep always an
* head object into lists so that frequent allocation from the
* free witness pool (and subsequent locking) is avoided.
* In order to maintain the current code simple, when the head
* object is totally unloaded it means also that we do not have
* further objects in the list, so the list ownership needs to be
* hand over to another object if the current head needs to be freed.
*/
if ((*lock_list)->ll_count == 0) {
if (*lock_list == lle) {
if (lle->ll_next == NULL)
goto out;
} else
lle = *lock_list;
*lock_list = lle->ll_next;
witness_lock_list_free(lle);
}
out:
splx(s);
}
void
witness_thread_exit(struct proc *p)
{
struct lock_list_entry *lle;
int i, n, s;
lle = p->p_sleeplocks;
if (lle == NULL || panicstr != NULL || db_active)
return;
if (lle->ll_count != 0) {
for (n = 0; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
if (n == 0)
printf("witness: thread %p exiting "
"with the following locks held:\n",
p);
n++;
witness_list_lock(&lle->ll_children[i],
printf);
}
panic("thread %p cannot exit while holding sleeplocks", p);
}
KASSERT(lle->ll_next == NULL);
s = splhigh();
witness_lock_list_free(lle);
splx(s);
}
/*
* Warn if any locks other than 'lock' are held. Flags can be passed in to
* exempt Giant and sleepable locks from the checks as well. If any
* non-exempt locks are held, then a supplied message is printed to the
* output channel along with a list of the offending locks. If indicated in the
* flags then a failure results in a panic as well.
*/
int
witness_warn(int flags, struct lock_object *lock, const char *fmt, ...)
{
struct lock_list_entry *lock_list, *lle;
struct lock_instance *lock1;
struct proc *p;
va_list ap;
int i, n;
if (witness_cold || witness_watch < 1 || panicstr != NULL || db_active)
return (0);
n = 0;
p = curproc;
for (lle = p->p_sleeplocks; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
lock1 = &lle->ll_children[i];
if (lock1->li_lock == lock)
continue;
if (flags & WARN_KERNELOK &&
is_kernel_lock(lock1->li_lock))
continue;
if (flags & WARN_SLEEPOK &&
(lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
continue;
if (n == 0) {
printf("witness: ");
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
printf(" with the following %slocks held:\n",
(flags & WARN_SLEEPOK) != 0 ?
"non-sleepable " : "");
}
n++;
witness_list_lock(lock1, printf);
}
lock_list = witness_cpu[cpu_number()].wc_spinlocks;
if (lock_list != NULL && lock_list->ll_count != 0) {
/*
* We should only have one spinlock and as long as
* the flags cannot match for this locks class,
* check if the first spinlock is the one curproc
* should hold.
*/
lock1 = &lock_list->ll_children[lock_list->ll_count - 1];
if (lock_list->ll_count == 1 && lock_list->ll_next == NULL &&
lock1->li_lock == lock && n == 0)
return (0);
printf("witness: ");
va_start(ap, fmt);
vprintf(fmt, ap);
va_end(ap);
printf(" with the following %slocks held:\n",
(flags & WARN_SLEEPOK) != 0 ? "non-sleepable " : "");
n += witness_list_locks(&lock_list, printf);
}
if (n > 0) {
if (flags & WARN_PANIC)
panic("%s", __func__);
else
witness_debugger(1);
}
return (n);
}
static struct witness *
enroll(const struct lock_type *type, const char *subtype,
struct lock_class *lock_class)
{
struct witness *w;
struct witness_list *typelist;
KASSERT(type != NULL);
if (witness_watch < 0 || panicstr != NULL || db_active)
return (NULL);
if ((lock_class->lc_flags & LC_SPINLOCK)) {
typelist = &w_spin;
} else if ((lock_class->lc_flags & LC_SLEEPLOCK)) {
typelist = &w_sleep;
} else {
panic("lock class %s is not sleep or spin",
lock_class->lc_name);
return (NULL);
}
mtx_enter(&w_mtx);
w = witness_hash_get(type, subtype);
if (w)
goto found;
if ((w = witness_get()) == NULL)
return (NULL);
w->w_type = type;
w->w_subtype = subtype;
w->w_class = lock_class;
SLIST_INSERT_HEAD(&w_all, w, w_list);
if (lock_class->lc_flags & LC_SPINLOCK) {
SLIST_INSERT_HEAD(&w_spin, w, w_typelist);
w_spin_cnt++;
} else if (lock_class->lc_flags & LC_SLEEPLOCK) {
SLIST_INSERT_HEAD(&w_sleep, w, w_typelist);
w_sleep_cnt++;
}
/* Insert new witness into the hash */
witness_hash_put(w);
witness_increment_graph_generation();
mtx_leave(&w_mtx);
return (w);
found:
mtx_leave(&w_mtx);
if (lock_class != w->w_class)
panic("lock (%s) %s does not match earlier (%s) lock",
type->lt_name, lock_class->lc_name, w->w_class->lc_name);
return (w);
}
static void
adopt(struct witness *parent, struct witness *child)
{
int pi, ci, i, j;
if (witness_cold == 0)
MUTEX_ASSERT_LOCKED(&w_mtx);
/* If the relationship is already known, there's no work to be done. */
if (isitmychild(parent, child))
return;
/* When the structure of the graph changes, bump up the generation. */
witness_increment_graph_generation();
/*
* The hard part ... create the direct relationship, then propagate all
* indirect relationships.
*/
pi = parent->w_index;
ci = child->w_index;
WITNESS_INDEX_ASSERT(pi);
WITNESS_INDEX_ASSERT(ci);
KASSERT(pi != ci);
w_rmatrix[pi][ci] |= WITNESS_PARENT;
w_rmatrix[ci][pi] |= WITNESS_CHILD;
/*
* If parent was not already an ancestor of child,
* then we increment the descendant and ancestor counters.
*/
if ((w_rmatrix[pi][ci] & WITNESS_ANCESTOR) == 0) {
parent->w_num_descendants++;
child->w_num_ancestors++;
}
/*
* Find each ancestor of 'pi'. Note that 'pi' itself is counted as
* an ancestor of 'pi' during this loop.
*/
for (i = 1; i <= w_max_used_index; i++) {
if ((w_rmatrix[i][pi] & WITNESS_ANCESTOR_MASK) == 0 &&
(i != pi))
continue;
/* Find each descendant of 'i' and mark it as a descendant. */
for (j = 1; j <= w_max_used_index; j++) {
/*
* Skip children that are already marked as
* descendants of 'i'.
*/
if (w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK)
continue;
/*
* We are only interested in descendants of 'ci'. Note
* that 'ci' itself is counted as a descendant of 'ci'.
*/
if ((w_rmatrix[ci][j] & WITNESS_ANCESTOR_MASK) == 0 &&
(j != ci))
continue;
w_rmatrix[i][j] |= WITNESS_ANCESTOR;
w_rmatrix[j][i] |= WITNESS_DESCENDANT;
w_data[i].w_num_descendants++;
w_data[j].w_num_ancestors++;
/*
* Make sure we aren't marking a node as both an
* ancestor and descendant. We should have caught
* this as a lock order reversal earlier.
*/
if ((w_rmatrix[i][j] & WITNESS_ANCESTOR_MASK) &&
(w_rmatrix[i][j] & WITNESS_DESCENDANT_MASK)) {
printf("witness: rmatrix paradox! [%d][%d]=%d "
"both ancestor and descendant\n",
i, j, w_rmatrix[i][j]);
#ifdef DDB
db_stack_dump();
#endif
printf("witness disabled\n");
witness_watch = -1;
}
if ((w_rmatrix[j][i] & WITNESS_ANCESTOR_MASK) &&
(w_rmatrix[j][i] & WITNESS_DESCENDANT_MASK)) {
printf("witness: rmatrix paradox! [%d][%d]=%d "
"both ancestor and descendant\n",
j, i, w_rmatrix[j][i]);
#ifdef DDB
db_stack_dump();
#endif
printf("witness disabled\n");
witness_watch = -1;
}
}
}
}
static void
itismychild(struct witness *parent, struct witness *child)
{
KASSERT(child != NULL && parent != NULL);
if (witness_cold == 0)
MUTEX_ASSERT_LOCKED(&w_mtx);
if (!witness_lock_type_equal(parent, child)) {
if (witness_cold == 0)
mtx_leave(&w_mtx);
panic(
"%s: parent \"%s\" (%s) and child \"%s\" (%s) are not "
"the same lock type", __func__, parent->w_type->lt_name,
parent->w_class->lc_name, child->w_type->lt_name,
child->w_class->lc_name);
}
adopt(parent, child);
}
/*
* Generic code for the isitmy*() functions. The rmask parameter is the
* expected relationship of w1 to w2.
*/
static int
_isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname)
{
unsigned char r1, r2;
int i1, i2;
i1 = w1->w_index;
i2 = w2->w_index;
WITNESS_INDEX_ASSERT(i1);
WITNESS_INDEX_ASSERT(i2);
r1 = w_rmatrix[i1][i2] & WITNESS_RELATED_MASK;
r2 = w_rmatrix[i2][i1] & WITNESS_RELATED_MASK;
/* The flags on one better be the inverse of the flags on the other */
if (!((WITNESS_ATOD(r1) == r2 && WITNESS_DTOA(r2) == r1) ||
(WITNESS_DTOA(r1) == r2 && WITNESS_ATOD(r2) == r1))) {
/* Don't squawk if we're potentially racing with an update. */
if (w_mtx.mtx_owner != curcpu())
return (0);
printf("witness: %s: rmatrix mismatch between %s (index %d) "
"and %s (index %d): w_rmatrix[%d][%d] == %x but "
"w_rmatrix[%d][%d] == %x\n",
fname, w1->w_type->lt_name, i1, w2->w_type->lt_name,
i2, i1, i2, r1,
i2, i1, r2);
#ifdef DDB
db_stack_dump();
#endif
printf("witness disabled\n");
witness_watch = -1;
}
return (r1 & rmask);
}
/*
* Checks if @child is a direct child of @parent.
*/
static int
isitmychild(struct witness *parent, struct witness *child)
{
return (_isitmyx(parent, child, WITNESS_PARENT, __func__));
}
/*
* Checks if @descendant is a direct or indirect descendant of @ancestor.
*/
static int
isitmydescendant(struct witness *ancestor, struct witness *descendant)
{
return (_isitmyx(ancestor, descendant, WITNESS_ANCESTOR_MASK,
__func__));
}
static struct witness *
witness_get(void)
{
struct witness *w;
int index;
if (witness_cold == 0)
MUTEX_ASSERT_LOCKED(&w_mtx);
if (witness_watch < 0) {
mtx_leave(&w_mtx);
return (NULL);
}
if (SLIST_EMPTY(&w_free)) {
witness_watch = -1;
mtx_leave(&w_mtx);
printf("WITNESS: unable to allocate a new witness object\n");
return (NULL);
}
w = SLIST_FIRST(&w_free);
SLIST_REMOVE_HEAD(&w_free, w_list);
w_free_cnt--;
index = w->w_index;
KASSERT(index > 0 && index == w_max_used_index + 1 &&
index < witness_count);
memset(w, 0, sizeof(*w));
w->w_index = index;
if (index > w_max_used_index)
w_max_used_index = index;
return (w);
}
static void
witness_free(struct witness *w)
{
SLIST_INSERT_HEAD(&w_free, w, w_list);
w_free_cnt++;
}
static struct lock_list_entry *
witness_lock_list_get(void)
{
struct lock_list_entry *lle;
struct witness_cpu *wcpu = &witness_cpu[cpu_number()];
if (witness_watch < 0)
return (NULL);
splassert(IPL_HIGH);
if (wcpu->wc_lle_count > 0) {
lle = wcpu->wc_lle_cache;
wcpu->wc_lle_cache = lle->ll_next;
wcpu->wc_lle_count--;
memset(lle, 0, sizeof(*lle));
return (lle);
}
mtx_enter(&w_mtx);
lle = w_lock_list_free;
if (lle == NULL) {
witness_watch = -1;
mtx_leave(&w_mtx);
printf("%s: witness exhausted\n", __func__);
return (NULL);
}
w_lock_list_free = lle->ll_next;
mtx_leave(&w_mtx);
memset(lle, 0, sizeof(*lle));
return (lle);
}
static void
witness_lock_list_free(struct lock_list_entry *lle)
{
struct witness_cpu *wcpu = &witness_cpu[cpu_number()];
splassert(IPL_HIGH);
if (wcpu->wc_lle_count < WITNESS_LLE_CACHE_MAX) {
lle->ll_next = wcpu->wc_lle_cache;
wcpu->wc_lle_cache = lle;
wcpu->wc_lle_count++;
return;
}
mtx_enter(&w_mtx);
lle->ll_next = w_lock_list_free;
w_lock_list_free = lle;
mtx_leave(&w_mtx);
}
static union lock_stack *
witness_lock_stack_get(void)
{
union lock_stack *stack = NULL;
struct witness_cpu *wcpu = &witness_cpu[cpu_number()];
splassert(IPL_HIGH);
if (wcpu->wc_stk_count > 0) {
stack = wcpu->wc_stk_cache;
wcpu->wc_stk_cache = stack->ls_next;
wcpu->wc_stk_count--;
return (stack);
}
mtx_enter(&w_mtx);
if (w_lock_stack_free != NULL) {
stack = w_lock_stack_free;
w_lock_stack_free = stack->ls_next;
}
mtx_leave(&w_mtx);
return (stack);
}
static void
witness_lock_stack_free(union lock_stack *stack)
{
struct witness_cpu *wcpu = &witness_cpu[cpu_number()];
splassert(IPL_HIGH);
if (wcpu->wc_stk_count < WITNESS_STK_CACHE_MAX) {
stack->ls_next = wcpu->wc_stk_cache;
wcpu->wc_stk_cache = stack;
wcpu->wc_stk_count++;
return;
}
mtx_enter(&w_mtx);
stack->ls_next = w_lock_stack_free;
w_lock_stack_free = stack;
mtx_leave(&w_mtx);
}
static struct lock_instance *
find_instance(struct lock_list_entry *list, const struct lock_object *lock)
{
struct lock_list_entry *lle;
struct lock_instance *instance;
int i;
for (lle = list; lle != NULL; lle = lle->ll_next) {
for (i = lle->ll_count - 1; i >= 0; i--) {
instance = &lle->ll_children[i];
if (instance->li_lock == lock)
return (instance);
}
}
return (NULL);
}
static void
witness_list_lock(struct lock_instance *instance,
int (*prnt)(const char *fmt, ...))
{
struct lock_object *lock;
lock = instance->li_lock;
prnt("%s %s %s", (instance->li_flags & LI_EXCLUSIVE) != 0 ?
"exclusive" : "shared", LOCK_CLASS(lock)->lc_name, lock->lo_name);
prnt(" r = %d (%p)\n", instance->li_flags & LI_RECURSEMASK, lock);
if (instance->li_stack != NULL)
stacktrace_print(&instance->li_stack->ls_stack, prnt);
}
static int
witness_search(struct witness *w, struct witness *target,
struct witness **path, int depth, int *remaining)
{
int i, any_remaining;
if (depth == 0) {
*remaining = 1;
return (w == target);
}
any_remaining = 0;
for (i = 1; i <= w_max_used_index; i++) {
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
if (witness_search(&w_data[i], target, path, depth - 1,
remaining)) {
path[depth - 1] = &w_data[i];
*remaining = 1;
return 1;
}
if (remaining)
any_remaining = 1;
}
}
*remaining = any_remaining;
return 0;
}
static void
witness_print_cycle_edge(int(*prnt)(const char *fmt, ...),
struct witness *parent, struct witness *child, int step, int last)
{
struct witness_lock_order_data *wlod;
int next;
if (last)
next = 1;
else
next = step + 1;
prnt("lock order [%d] %s (%s) -> [%d] %s (%s)\n",
step, parent->w_subtype, parent->w_type->lt_name,
next, child->w_subtype, child->w_type->lt_name);
if (witness_watch > 1) {
mtx_enter(&w_mtx);
wlod = witness_lock_order_get(parent, child);
mtx_leave(&w_mtx);
if (wlod != NULL)
stacktrace_print(&wlod->wlod_stack, printf);
else
prnt("lock order data %p -> %p is missing\n",
parent->w_type->lt_name, child->w_type->lt_name);
}
}
static void
witness_print_cycle(int(*prnt)(const char *fmt, ...),
struct witness *parent, struct witness *child)
{
struct witness *path[4];
struct witness *w;
int depth, remaining;
int step = 0;
/*
* Use depth-limited search to find the shortest path
* from child to parent.
*/
for (depth = 1; depth < nitems(path); depth++) {
if (witness_search(child, parent, path, depth, &remaining))
goto found;
if (!remaining)
break;
}
prnt("witness: incomplete path, depth %d\n", depth);
return;
found:
witness_print_cycle_edge(prnt, parent, child, ++step, 0);
for (w = child; depth > 0; depth--) {
witness_print_cycle_edge(prnt, w, path[depth - 1], ++step,
depth == 1);
w = path[depth - 1];
}
}
#ifdef DDB
static int
witness_thread_has_locks(struct proc *p)
{
if (p->p_sleeplocks == NULL)
return (0);
return (p->p_sleeplocks->ll_count != 0);
}
static int
witness_process_has_locks(struct process *pr)
{
struct proc *p;
TAILQ_FOREACH(p, &pr->ps_threads, p_thr_link) {
if (witness_thread_has_locks(p))
return (1);
}
return (0);
}
#endif
int
witness_list_locks(struct lock_list_entry **lock_list,
int (*prnt)(const char *fmt, ...))
{
struct lock_list_entry *lle;
int i, nheld;
nheld = 0;
for (lle = *lock_list; lle != NULL; lle = lle->ll_next)
for (i = lle->ll_count - 1; i >= 0; i--) {
witness_list_lock(&lle->ll_children[i], prnt);
nheld++;
}
return (nheld);
}
/*
* This is a bit risky at best. We call this function when we have timed
* out acquiring a spin lock, and we assume that the other CPU is stuck
* with this lock held. So, we go groveling around in the other CPU's
* per-cpu data to try to find the lock instance for this spin lock to
* see when it was last acquired.
*/
void
witness_display_spinlock(struct lock_object *lock, struct proc *owner,
int (*prnt)(const char *fmt, ...))
{
struct lock_instance *instance;
if (owner->p_stat != SONPROC)
return;
instance = find_instance(
witness_cpu[owner->p_cpu->ci_cpuid].wc_spinlocks, lock);
if (instance != NULL)
witness_list_lock(instance, prnt);
}
void
witness_assert(const struct lock_object *lock, int flags)
{
struct lock_instance *instance;
struct lock_class *class;
if (lock->lo_witness == NULL || witness_watch < 1 ||
panicstr != NULL || db_active)
return;
class = LOCK_CLASS(lock);
if ((class->lc_flags & LC_SLEEPLOCK) != 0)
instance = find_instance(curproc->p_sleeplocks, lock);
else if ((class->lc_flags & LC_SPINLOCK) != 0)
instance = find_instance(
witness_cpu[cpu_number()].wc_spinlocks, lock);
else {
panic("lock (%s) %s is not sleep or spin!",
class->lc_name, lock->lo_name);
return;
}
switch (flags) {
case LA_UNLOCKED:
if (instance != NULL)
panic("lock (%s) %s locked",
class->lc_name, lock->lo_name);
break;
case LA_LOCKED:
case LA_LOCKED | LA_RECURSED:
case LA_LOCKED | LA_NOTRECURSED:
case LA_SLOCKED:
case LA_SLOCKED | LA_RECURSED:
case LA_SLOCKED | LA_NOTRECURSED:
case LA_XLOCKED:
case LA_XLOCKED | LA_RECURSED:
case LA_XLOCKED | LA_NOTRECURSED:
if (instance == NULL) {
panic("lock (%s) %s not locked",
class->lc_name, lock->lo_name);
break;
}
if ((flags & LA_XLOCKED) != 0 &&
(instance->li_flags & LI_EXCLUSIVE) == 0)
panic(
"lock (%s) %s not exclusively locked",
class->lc_name, lock->lo_name);
if ((flags & LA_SLOCKED) != 0 &&
(instance->li_flags & LI_EXCLUSIVE) != 0)
panic(
"lock (%s) %s exclusively locked",
class->lc_name, lock->lo_name);
if ((flags & LA_RECURSED) != 0 &&
(instance->li_flags & LI_RECURSEMASK) == 0)
panic("lock (%s) %s not recursed",
class->lc_name, lock->lo_name);
if ((flags & LA_NOTRECURSED) != 0 &&
(instance->li_flags & LI_RECURSEMASK) != 0)
panic("lock (%s) %s recursed",
class->lc_name, lock->lo_name);
break;
default:
panic("invalid lock assertion");
}
}
static void
witness_setflag(struct lock_object *lock, int flag, int set)
{
struct lock_list_entry *lock_list;
struct lock_instance *instance;
struct lock_class *class;
if (lock->lo_witness == NULL || witness_watch < 0 ||
panicstr != NULL || db_active)
return;
class = LOCK_CLASS(lock);
if (class->lc_flags & LC_SLEEPLOCK)
lock_list = curproc->p_sleeplocks;
else
lock_list = witness_cpu[cpu_number()].wc_spinlocks;
instance = find_instance(lock_list, lock);
if (instance == NULL) {
panic("%s: lock (%s) %s not locked", __func__,
class->lc_name, lock->lo_name);
return;
}
if (set)
instance->li_flags |= flag;
else
instance->li_flags &= ~flag;
}
void
witness_norelease(struct lock_object *lock)
{
witness_setflag(lock, LI_NORELEASE, 1);
}
void
witness_releaseok(struct lock_object *lock)
{
witness_setflag(lock, LI_NORELEASE, 0);
}
#ifdef DDB
static void
witness_ddb_list(struct proc *p)
{
struct witness_cpu *wc = &witness_cpu[cpu_number()];
KASSERTMSG(witness_cold == 0, "%s: witness_cold", __func__);
KASSERTMSG(db_active, "%s: not in the debugger", __func__);
if (witness_watch < 1)
return;
witness_list_locks(&p->p_sleeplocks, db_printf);
/*
* We only handle spinlocks if td == curproc. This is somewhat broken
* if td is currently executing on some other CPU and holds spin locks
* as we won't display those locks. If we had a MI way of getting
* the per-cpu data for a given cpu then we could use
* td->td_oncpu to get the list of spinlocks for this thread
* and "fix" this.
*
* That still wouldn't really fix this unless we locked the scheduler
* lock or stopped the other CPU to make sure it wasn't changing the
* list out from under us. It is probably best to just not try to
* handle threads on other CPU's for now.
*/
if (p == curproc && wc->wc_spinlocks != NULL)
witness_list_locks(&wc->wc_spinlocks, db_printf);
}
void
db_witness_list(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
{
struct proc *p;
if (have_addr)
p = (struct proc *)addr;
else
p = curproc;
witness_ddb_list(p);
}
void
db_witness_list_all(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
{
CPU_INFO_ITERATOR cii;
struct cpu_info *ci;
struct lock_list_entry *lock_list;
struct process *pr;
struct proc *p;
CPU_INFO_FOREACH(cii, ci) {
lock_list = witness_cpu[CPU_INFO_UNIT(ci)].wc_spinlocks;
if (lock_list == NULL || lock_list->ll_count == 0)
continue;
db_printf("CPU %d:\n", CPU_INFO_UNIT(ci));
witness_list_locks(&lock_list, db_printf);
}
/*
* It would be nice to list only threads and processes that actually
* held sleep locks, but that information is currently not exported
* by WITNESS.
*/
LIST_FOREACH(pr, &allprocess, ps_list) {
if (!witness_process_has_locks(pr))
continue;
TAILQ_FOREACH(p, &pr->ps_threads, p_thr_link) {
if (!witness_thread_has_locks(p))
continue;
db_printf("Process %d (%s) thread %p (%d)\n",
pr->ps_pid, pr->ps_comm, p, p->p_tid);
witness_ddb_list(p);
}
}
}
void
witness_print_badstacks(void)
{
struct witness *w1, *w2;
int error, generation, i, j;
if (witness_watch < 1) {
db_printf("witness watch is disabled\n");
return;
}
if (witness_cold) {
db_printf("witness is cold\n");
return;
}
error = 0;
restart:
mtx_enter(&w_mtx);
generation = w_generation;
mtx_leave(&w_mtx);
db_printf("Number of known direct relationships is %d\n",
w_lohash.wloh_count);
for (i = 1; i < w_max_used_index; i++) {
mtx_enter(&w_mtx);
if (generation != w_generation) {
mtx_leave(&w_mtx);
/* The graph has changed, try again. */
db_printf("Lock graph changed, restarting trace.\n");
goto restart;
}
w1 = &w_data[i];
if (w1->w_reversed == 0) {
mtx_leave(&w_mtx);
continue;
}
mtx_leave(&w_mtx);
if (w1->w_reversed == 0)
continue;
for (j = 1; j < w_max_used_index; j++) {
if ((w_rmatrix[i][j] & WITNESS_REVERSAL) == 0 || i > j)
continue;
mtx_enter(&w_mtx);
if (generation != w_generation) {
mtx_leave(&w_mtx);
/* The graph has changed, try again. */
db_printf("Lock graph changed, "
"restarting trace.\n");
goto restart;
}
w2 = &w_data[j];
mtx_leave(&w_mtx);
db_printf("\nLock order reversal between \"%s\"(%s) "
"and \"%s\"(%s)!\n",
w1->w_type->lt_name, w1->w_class->lc_name,
w2->w_type->lt_name, w2->w_class->lc_name);
witness_print_cycle(db_printf, w1, w2);
}
}
mtx_enter(&w_mtx);
if (generation != w_generation) {
mtx_leave(&w_mtx);
/*
* The graph changed while we were printing stack data,
* try again.
*/
db_printf("Lock graph changed, restarting trace.\n");
goto restart;
}
mtx_leave(&w_mtx);
}
void
db_witness_display(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
{
switch (modif[0]) {
case 'b':
witness_print_badstacks();
break;
default:
witness_ddb_display(db_printf);
break;
}
}
#endif
void
db_witness_print_fullgraph(void)
{
struct witness *w;
int error;
if (witness_watch < 1) {
db_printf("witness watch is disabled\n");
return;
}
if (witness_cold) {
db_printf("witness is cold\n");
return;
}
error = 0;
mtx_enter(&w_mtx);
SLIST_FOREACH(w, &w_all, w_list)
w->w_displayed = 0;
SLIST_FOREACH(w, &w_all, w_list)
db_witness_add_fullgraph(w);
mtx_leave(&w_mtx);
}
static void
db_witness_add_fullgraph(struct witness *w)
{
int i;
if (w->w_displayed != 0 || w->w_acquired == 0)
return;
w->w_displayed = 1;
WITNESS_INDEX_ASSERT(w->w_index);
for (i = 1; i <= w_max_used_index; i++) {
if (w_rmatrix[w->w_index][i] & WITNESS_PARENT) {
db_printf("\"%s\",\"%s\"\n", w->w_type->lt_name,
w_data[i].w_type->lt_name);
db_witness_add_fullgraph(&w_data[i]);
}
}
}
/*
* A simple hash function. Takes a key pointer and a key size. If size == 0,
* interprets the key as a string and reads until the null
* terminator. Otherwise, reads the first size bytes. Returns an unsigned 32-bit
* hash value computed from the key.
*/
static uint32_t
witness_hash_djb2(const uint8_t *key, uint32_t size)
{
unsigned int hash = 5381;
int i;
/* hash = hash * 33 + key[i] */
if (size)
for (i = 0; i < size; i++)
hash = ((hash << 5) + hash) + (unsigned int)key[i];
else
for (i = 0; key[i] != 0; i++)
hash = ((hash << 5) + hash) + (unsigned int)key[i];
return (hash);
}
/*
* Initializes the two witness hash tables. Called exactly once from
* witness_initialize().
*/
static void
witness_init_hash_tables(void)
{
int i;
KASSERT(witness_cold);
/* Initialize the hash tables. */
for (i = 0; i < WITNESS_HASH_SIZE; i++)
SLIST_INIT(&w_hash.wh_array[i]);
w_hash.wh_size = WITNESS_HASH_SIZE;
w_hash.wh_count = 0;
/* Initialize the lock order data hash. */
w_lodata = (void *)uvm_pageboot_alloc(
sizeof(struct witness_lock_order_data) * WITNESS_LO_DATA_COUNT);
memset(w_lodata, 0, sizeof(struct witness_lock_order_data) *
WITNESS_LO_DATA_COUNT);
w_lofree = NULL;
for (i = 0; i < WITNESS_LO_DATA_COUNT; i++) {
w_lodata[i].wlod_next = w_lofree;
w_lofree = &w_lodata[i];
}
w_lohash.wloh_size = WITNESS_LO_HASH_SIZE;
w_lohash.wloh_count = 0;
for (i = 0; i < WITNESS_LO_HASH_SIZE; i++)
w_lohash.wloh_array[i] = NULL;
}
static struct witness *
witness_hash_get(const struct lock_type *type, const char *subtype)
{
struct witness *w;
uint32_t hash;
KASSERT(type != NULL);
if (witness_cold == 0)
MUTEX_ASSERT_LOCKED(&w_mtx);
hash = (uint32_t)((uintptr_t)type ^ (uintptr_t)subtype) %
w_hash.wh_size;
SLIST_FOREACH(w, &w_hash.wh_array[hash], w_hash_next) {
if (w->w_type == type && w->w_subtype == subtype)
goto out;
}
out:
return (w);
}
static void
witness_hash_put(struct witness *w)
{
uint32_t hash;
KASSERT(w != NULL);
KASSERT(w->w_type != NULL);
if (witness_cold == 0)
MUTEX_ASSERT_LOCKED(&w_mtx);
KASSERTMSG(witness_hash_get(w->w_type, w->w_subtype) == NULL,
"%s: trying to add a hash entry that already exists!", __func__);
KASSERTMSG(SLIST_NEXT(w, w_hash_next) == NULL,
"%s: w->w_hash_next != NULL", __func__);
hash = (uint32_t)((uintptr_t)w->w_type ^ (uintptr_t)w->w_subtype) %
w_hash.wh_size;
SLIST_INSERT_HEAD(&w_hash.wh_array[hash], w, w_hash_next);
w_hash.wh_count++;
}
static struct witness_lock_order_data *
witness_lock_order_get(struct witness *parent, struct witness *child)
{
struct witness_lock_order_data *data = NULL;
struct witness_lock_order_key key;
unsigned int hash;
KASSERT(parent != NULL && child != NULL);
key.from = parent->w_index;
key.to = child->w_index;
WITNESS_INDEX_ASSERT(key.from);
WITNESS_INDEX_ASSERT(key.to);
if ((w_rmatrix[parent->w_index][child->w_index]
& WITNESS_LOCK_ORDER_KNOWN) == 0)
goto out;
hash = witness_hash_djb2((const char*)&key,
sizeof(key)) % w_lohash.wloh_size;
data = w_lohash.wloh_array[hash];
while (data != NULL) {
if (witness_lock_order_key_equal(&data->wlod_key, &key))
break;
data = data->wlod_next;
}
out:
return (data);
}
/*
* Verify that parent and child have a known relationship, are not the same,
* and child is actually a child of parent. This is done without w_mtx
* to avoid contention in the common case.
*/
static int
witness_lock_order_check(struct witness *parent, struct witness *child)
{
if (parent != child &&
w_rmatrix[parent->w_index][child->w_index]
& WITNESS_LOCK_ORDER_KNOWN &&
isitmychild(parent, child))
return (1);
return (0);
}
static int
witness_lock_order_add(struct witness *parent, struct witness *child)
{
static int lofree_empty_reported = 0;
struct witness_lock_order_data *data = NULL;
struct witness_lock_order_key key;
unsigned int hash;
KASSERT(parent != NULL && child != NULL);
key.from = parent->w_index;
key.to = child->w_index;
WITNESS_INDEX_ASSERT(key.from);
WITNESS_INDEX_ASSERT(key.to);
if (w_rmatrix[parent->w_index][child->w_index]
& WITNESS_LOCK_ORDER_KNOWN)
return (1);
hash = witness_hash_djb2((const char*)&key,
sizeof(key)) % w_lohash.wloh_size;
w_rmatrix[parent->w_index][child->w_index] |= WITNESS_LOCK_ORDER_KNOWN;
data = w_lofree;
if (data == NULL) {
if (!lofree_empty_reported) {
lofree_empty_reported = 1;
printf("witness: out of free lock order entries\n");
}
return (0);
}
w_lofree = data->wlod_next;
data->wlod_next = w_lohash.wloh_array[hash];
data->wlod_key = key;
w_lohash.wloh_array[hash] = data;
w_lohash.wloh_count++;
stacktrace_save_at(&data->wlod_stack, 1);
return (1);
}
/* Call this whenever the structure of the witness graph changes. */
static void
witness_increment_graph_generation(void)
{
if (witness_cold == 0)
MUTEX_ASSERT_LOCKED(&w_mtx);
w_generation++;
}
static void
witness_debugger(int dump)
{
switch (witness_watch) {
case 1:
break;
case 2:
if (dump)
db_stack_dump();
break;
case 3:
if (dump)
db_stack_dump();
db_enter();
break;
default:
panic("witness: locking error");
}
}
static int
witness_alloc_stacks(void)
{
union lock_stack *stacks;
unsigned int i, nstacks = LOCK_CHILDCOUNT * LOCK_NCHILDREN;
rw_assert_wrlock(&w_ctlock);
if (w_lock_stack_num >= nstacks)
return (0);
nstacks -= w_lock_stack_num;
stacks = mallocarray(nstacks, sizeof(*stacks), M_WITNESS,
M_WAITOK | M_CANFAIL | M_ZERO);
if (stacks == NULL)
return (ENOMEM);
mtx_enter(&w_mtx);
for (i = 0; i < nstacks; i++) {
stacks[i].ls_next = w_lock_stack_free;
w_lock_stack_free = &stacks[i];
}
mtx_leave(&w_mtx);
w_lock_stack_num += nstacks;
return (0);
}
int
witness_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
void *newp, size_t newlen)
{
int error, value;
if (namelen != 1)
return (ENOTDIR);
rw_enter_write(&w_ctlock);
switch (name[0]) {
case KERN_WITNESS_WATCH:
error = witness_sysctl_watch(oldp, oldlenp, newp, newlen);
break;
case KERN_WITNESS_LOCKTRACE:
value = witness_locktrace;
error = sysctl_int(oldp, oldlenp, newp, newlen, &value);
if (error == 0 && newp != NULL) {
switch (value) {
case 1:
error = witness_alloc_stacks();
/* FALLTHROUGH */
case 0:
if (error == 0)
witness_locktrace = value;
break;
default:
error = EINVAL;
break;
}
}
break;
default:
error = EOPNOTSUPP;
break;
}
rw_exit_write(&w_ctlock);
return (error);
}
int
witness_sysctl_watch(void *oldp, size_t *oldlenp, void *newp, size_t newlen)
{
int error;
int value;
value = witness_watch;
error = sysctl_int_bounded(oldp, oldlenp, newp, newlen,
&value, -1, 3);
if (error == 0 && newp != NULL) {
mtx_enter(&w_mtx);
if (value < 0 || witness_watch >= 0)
witness_watch = value;
else
error = EINVAL;
mtx_leave(&w_mtx);
}
return (error);
}
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