1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
|
/*-
* Copyright (c) 2001 Matthew Dillon. All Rights Reserved. Copyright
* terms are as specified in the COPYRIGHT file at the base of the source
* tree.
*
* Mutex pool routines. These routines are designed to be used as short
* term leaf mutexes (e.g. the last mutex you might aquire other then
* calling msleep()). They operate using a shared pool. A mutex is chosen
* from the pool based on the supplied pointer (which may or may not be
* valid).
*
* Advantages:
* - no structural overhead. Mutexes can be associated with structures
* without adding bloat to the structures.
* - mutexes can be obtained for invalid pointers, useful when uses
* mutexes to interlock destructor ops.
* - no initialization/destructor overhead.
* - can be used with msleep.
*
* Disadvantages:
* - should generally only be used as leaf mutexes.
* - pool/pool dependancy ordering cannot be depended on.
* - possible L1 cache mastersip contention between cpus.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/systm.h>
MALLOC_DEFINE(M_MTXPOOL, "mtx_pool", "mutex pool");
/* Pool sizes must be a power of two */
#ifndef MTX_POOL_LOCKBUILDER_SIZE
#define MTX_POOL_LOCKBUILDER_SIZE 128
#endif
#ifndef MTX_POOL_SLEEP_SIZE
#define MTX_POOL_SLEEP_SIZE 128
#endif
struct mtxpool_header {
int mtxpool_size;
int mtxpool_mask;
int mtxpool_shift;
int mtxpool_next;
};
struct mtx_pool {
struct mtxpool_header mtx_pool_header;
struct mtx mtx_pool_ary[1];
};
static struct mtx_pool_lockbuilder {
struct mtxpool_header mtx_pool_header;
struct mtx mtx_pool_ary[MTX_POOL_LOCKBUILDER_SIZE];
} lockbuilder_pool;
#define mtx_pool_size mtx_pool_header.mtxpool_size
#define mtx_pool_mask mtx_pool_header.mtxpool_mask
#define mtx_pool_shift mtx_pool_header.mtxpool_shift
#define mtx_pool_next mtx_pool_header.mtxpool_next
struct mtx_pool *mtxpool_sleep;
struct mtx_pool *mtxpool_lockbuilder;
#if UINTPTR_MAX == UINT64_MAX /* 64 bits */
# define POINTER_BITS 64
# define HASH_MULTIPLIER 11400714819323198485u /* (2^64)*(sqrt(5)-1)/2 */
#else /* assume 32 bits */
# define POINTER_BITS 32
# define HASH_MULTIPLIER 2654435769u /* (2^32)*(sqrt(5)-1)/2 */
#endif
/*
* Return the (shared) pool mutex associated with the specified address.
* The returned mutex is a leaf level mutex, meaning that if you obtain it
* you cannot obtain any other mutexes until you release it. You can
* legally msleep() on the mutex.
*/
struct mtx *
mtx_pool_find(struct mtx_pool *pool, void *ptr)
{
int p;
KASSERT(pool != NULL, ("_mtx_pool_find(): null pool"));
/*
* Fibonacci hash, see Knuth's
* _Art of Computer Programming, Volume 3 / Sorting and Searching_
*/
p = ((HASH_MULTIPLIER * (uintptr_t)ptr) >> pool->mtx_pool_shift) &
pool->mtx_pool_mask;
return (&pool->mtx_pool_ary[p]);
}
static void
mtx_pool_initialize(struct mtx_pool *pool, const char *mtx_name, int pool_size,
int opts)
{
int i, maskbits;
pool->mtx_pool_size = pool_size;
pool->mtx_pool_mask = pool_size - 1;
for (i = 1, maskbits = 0; (i & pool_size) == 0; i = i << 1)
maskbits++;
pool->mtx_pool_shift = POINTER_BITS - maskbits;
pool->mtx_pool_next = 0;
for (i = 0; i < pool_size; ++i)
mtx_init(&pool->mtx_pool_ary[i], mtx_name, NULL, opts);
}
struct mtx_pool *
mtx_pool_create(const char *mtx_name, int pool_size, int opts)
{
struct mtx_pool *pool;
if (pool_size <= 0 || !powerof2(pool_size)) {
printf("WARNING: %s pool size is not a power of 2.\n",
mtx_name);
pool_size = 128;
}
MALLOC(pool, struct mtx_pool *,
sizeof (struct mtx_pool) + ((pool_size - 1) * sizeof (struct mtx)),
M_MTXPOOL, M_WAITOK | M_ZERO);
mtx_pool_initialize(pool, mtx_name, pool_size, opts);
return pool;
}
void
mtx_pool_destroy(struct mtx_pool **poolp)
{
int i;
struct mtx_pool *pool = *poolp;
for (i = pool->mtx_pool_size - 1; i >= 0; --i)
mtx_destroy(&pool->mtx_pool_ary[i]);
FREE(pool, M_MTXPOOL);
*poolp = NULL;
}
static void
mtx_pool_setup_static(void *dummy __unused)
{
mtx_pool_initialize((struct mtx_pool *)&lockbuilder_pool,
"lockbuilder mtxpool", MTX_POOL_LOCKBUILDER_SIZE,
MTX_DEF | MTX_NOWITNESS | MTX_QUIET);
mtxpool_lockbuilder = (struct mtx_pool *)&lockbuilder_pool;
}
static void
mtx_pool_setup_dynamic(void *dummy __unused)
{
mtxpool_sleep = mtx_pool_create("sleep mtxpool",
MTX_POOL_SLEEP_SIZE, MTX_DEF);
}
/*
* Obtain a (shared) mutex from the pool. The returned mutex is a leaf
* level mutex, meaning that if you obtain it you cannot obtain any other
* mutexes until you release it. You can legally msleep() on the mutex.
*/
struct mtx *
mtx_pool_alloc(struct mtx_pool *pool)
{
int i;
KASSERT(pool != NULL, ("mtx_pool_alloc(): null pool"));
/*
* mtx_pool_next is unprotected against multiple accesses,
* but simultaneous access by two CPUs should not be very
* harmful.
*/
i = pool->mtx_pool_next;
pool->mtx_pool_next = (i + 1) & pool->mtx_pool_mask;
return (&pool->mtx_pool_ary[i]);
}
/*
* The lockbuilder pool must be initialized early because the lockmgr
* and sx locks depend on it. The sx locks are used in the kernel
* memory allocator. The lockmgr subsystem is initialized by
* SYSINIT(..., SI_SUB_LOCKMGR, ...).
*
* We can't call MALLOC() to dynamically allocate the sleep pool
* until after kmeminit() has been called, which is done by
* SYSINIT(..., SI_SUB_KMEM, ...).
*/
SYSINIT(mtxpooli1, SI_SUB_MTX_POOL_STATIC, SI_ORDER_FIRST,
mtx_pool_setup_static, NULL);
SYSINIT(mtxpooli2, SI_SUB_MTX_POOL_DYNAMIC, SI_ORDER_FIRST,
mtx_pool_setup_dynamic, NULL);
|
