1 #define JEMALLOC_CHUNK_DSS_C_
2 #include "jemalloc/internal/jemalloc_internal.h"
3 /******************************************************************************/
4 /* Data. */
5
6 const char *dss_prec_names[] = {
7 "disabled",
8 "primary",
9 "secondary",
10 "N/A"
11 };
12
13 /* Current dss precedence default, used when creating new arenas. */
14 static dss_prec_t dss_prec_default = DSS_PREC_DEFAULT;
15
16 /*
17 * Protects sbrk() calls. This avoids malloc races among threads, though it
18 * does not protect against races with threads that call sbrk() directly.
19 */
20 static malloc_mutex_t dss_mtx;
21
22 /* Base address of the DSS. */
23 static void *dss_base;
24 /* Current end of the DSS, or ((void *)-1) if the DSS is exhausted. */
25 static void *dss_prev;
26 /* Current upper limit on DSS addresses. */
27 static void *dss_max;
28
29 /******************************************************************************/
30
31 static void *
chunk_dss_sbrk(intptr_t increment)32 chunk_dss_sbrk(intptr_t increment)
33 {
34
35 #ifdef JEMALLOC_DSS
36 return (sbrk(increment));
37 #else
38 not_implemented();
39 return (NULL);
40 #endif
41 }
42
43 dss_prec_t
chunk_dss_prec_get(void)44 chunk_dss_prec_get(void)
45 {
46 dss_prec_t ret;
47
48 if (!have_dss)
49 return (dss_prec_disabled);
50 malloc_mutex_lock(&dss_mtx);
51 ret = dss_prec_default;
52 malloc_mutex_unlock(&dss_mtx);
53 return (ret);
54 }
55
56 bool
chunk_dss_prec_set(dss_prec_t dss_prec)57 chunk_dss_prec_set(dss_prec_t dss_prec)
58 {
59
60 if (!have_dss)
61 return (dss_prec != dss_prec_disabled);
62 malloc_mutex_lock(&dss_mtx);
63 dss_prec_default = dss_prec;
64 malloc_mutex_unlock(&dss_mtx);
65 return (false);
66 }
67
68 void *
chunk_alloc_dss(arena_t * arena,void * new_addr,size_t size,size_t alignment,bool * zero)69 chunk_alloc_dss(arena_t *arena, void *new_addr, size_t size, size_t alignment,
70 bool *zero)
71 {
72 void *ret;
73
74 cassert(have_dss);
75 assert(size > 0 && (size & chunksize_mask) == 0);
76 assert(alignment > 0 && (alignment & chunksize_mask) == 0);
77
78 /*
79 * sbrk() uses a signed increment argument, so take care not to
80 * interpret a huge allocation request as a negative increment.
81 */
82 if ((intptr_t)size < 0)
83 return (NULL);
84
85 malloc_mutex_lock(&dss_mtx);
86 if (dss_prev != (void *)-1) {
87 size_t gap_size, cpad_size;
88 void *cpad, *dss_next;
89 intptr_t incr;
90
91 /*
92 * The loop is necessary to recover from races with other
93 * threads that are using the DSS for something other than
94 * malloc.
95 */
96 do {
97 /* Avoid an unnecessary system call. */
98 if (new_addr != NULL && dss_max != new_addr)
99 break;
100
101 /* Get the current end of the DSS. */
102 dss_max = chunk_dss_sbrk(0);
103
104 /* Make sure the earlier condition still holds. */
105 if (new_addr != NULL && dss_max != new_addr)
106 break;
107
108 /*
109 * Calculate how much padding is necessary to
110 * chunk-align the end of the DSS.
111 */
112 gap_size = (chunksize - CHUNK_ADDR2OFFSET(dss_max)) &
113 chunksize_mask;
114 /*
115 * Compute how much chunk-aligned pad space (if any) is
116 * necessary to satisfy alignment. This space can be
117 * recycled for later use.
118 */
119 cpad = (void *)((uintptr_t)dss_max + gap_size);
120 ret = (void *)ALIGNMENT_CEILING((uintptr_t)dss_max,
121 alignment);
122 cpad_size = (uintptr_t)ret - (uintptr_t)cpad;
123 dss_next = (void *)((uintptr_t)ret + size);
124 if ((uintptr_t)ret < (uintptr_t)dss_max ||
125 (uintptr_t)dss_next < (uintptr_t)dss_max) {
126 /* Wrap-around. */
127 malloc_mutex_unlock(&dss_mtx);
128 return (NULL);
129 }
130 incr = gap_size + cpad_size + size;
131 dss_prev = chunk_dss_sbrk(incr);
132 if (dss_prev == dss_max) {
133 /* Success. */
134 dss_max = dss_next;
135 malloc_mutex_unlock(&dss_mtx);
136 if (cpad_size != 0) {
137 chunk_record(arena,
138 &arena->chunks_szad_dss,
139 &arena->chunks_ad_dss, false, cpad,
140 cpad_size, false);
141 }
142 if (*zero) {
143 JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(
144 ret, size);
145 memset(ret, 0, size);
146 }
147 return (ret);
148 }
149 } while (dss_prev != (void *)-1);
150 }
151 malloc_mutex_unlock(&dss_mtx);
152
153 return (NULL);
154 }
155
156 bool
chunk_in_dss(void * chunk)157 chunk_in_dss(void *chunk)
158 {
159 bool ret;
160
161 cassert(have_dss);
162
163 malloc_mutex_lock(&dss_mtx);
164 if ((uintptr_t)chunk >= (uintptr_t)dss_base
165 && (uintptr_t)chunk < (uintptr_t)dss_max)
166 ret = true;
167 else
168 ret = false;
169 malloc_mutex_unlock(&dss_mtx);
170
171 return (ret);
172 }
173
174 bool
chunk_dss_boot(void)175 chunk_dss_boot(void)
176 {
177
178 cassert(have_dss);
179
180 if (malloc_mutex_init(&dss_mtx))
181 return (true);
182 dss_base = chunk_dss_sbrk(0);
183 dss_prev = dss_base;
184 dss_max = dss_base;
185
186 return (false);
187 }
188
189 void
chunk_dss_prefork(void)190 chunk_dss_prefork(void)
191 {
192
193 if (have_dss)
194 malloc_mutex_prefork(&dss_mtx);
195 }
196
197 void
chunk_dss_postfork_parent(void)198 chunk_dss_postfork_parent(void)
199 {
200
201 if (have_dss)
202 malloc_mutex_postfork_parent(&dss_mtx);
203 }
204
205 void
chunk_dss_postfork_child(void)206 chunk_dss_postfork_child(void)
207 {
208
209 if (have_dss)
210 malloc_mutex_postfork_child(&dss_mtx);
211 }
212
213 /******************************************************************************/
214