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subr_witness.c
2588 lines (2276 loc) · 68.6 KB
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subr_witness.c
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/* $OpenBSD: subr_witness.c,v 1.37 2020/03/15 05:58:48 visa 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;
SIMPLEQ_ENTRY(witness) w_list; /* List of all witnesses. */
SIMPLEQ_ENTRY(witness) w_typelist; /* Witnesses of a type. */
struct 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;
};
SIMPLEQ_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 *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_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;
static struct mutex w_mtx;
static struct rwlock w_ctlock = RWLOCK_INITIALIZER("w_ctlock");
/* w_list */
static struct witness_list w_free = SIMPLEQ_HEAD_INITIALIZER(w_free);
static struct witness_list w_all = SIMPLEQ_HEAD_INITIALIZER(w_all);
/* w_typelist */
static struct witness_list w_spin = SIMPLEQ_HEAD_INITIALIZER(w_spin);
static struct witness_list w_sleep = SIMPLEQ_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[LOCK_CHILDCOUNT];
static struct witness_hash w_hash; /* The witness hash table. */
/* The lock order data hash */
static struct witness_lock_order_data w_lodata[WITNESS_LO_DATA_COUNT];
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_sched_lock = {
.lc_name = "sched_lock",
.lc_flags = LC_SPINLOCK | LC_RECURSABLE
};
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_sched_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(SIMPLEQ_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. */
SIMPLEQ_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);
}
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.
*/
SIMPLEQ_FOREACH(w, &w_all, w_list)
w->w_ddb_level = -1;
/*
* Look for locks with no parents and level all their descendants.
*/
SIMPLEQ_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 (type: %s, depth: %d)",
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;
SIMPLEQ_FOREACH(w, list, w_typelist) {
if (!w->w_acquired || w->w_ddb_level > 0)
continue;
/* This lock has no anscestors - 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. */
SIMPLEQ_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");
SIMPLEQ_FOREACH(w, &w_all, w_list) {
if (w->w_acquired)
continue;
prnt("%s (type: %s, depth: %d)\n", 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 proc *p;
struct witness *w, *w1;
int i, j, s;
if (witness_cold || witness_watch < 1 || panicstr != NULL ||
db_active || (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);
p = curproc;
if (class->lc_flags & LC_SLEEPLOCK) {
/*
* 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.
*/
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 enfore 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 &&