projects/linux·blob master · refs

237 lines · 5.2 KiB

1// SPDX-License-Identifier: GPL-2.0
2#include "comm.h"
3#include <errno.h>
4#include <string.h>
5#include <internal/rc_check.h>
6#include <linux/refcount.h>
7#include <linux/zalloc.h>
8#include <tools/libc_compat.h> // reallocarray
9
10#include "rwsem.h"
11
12DECLARE_RC_STRUCT(comm_str) {
13 refcount_t refcnt;
14 char str[];
15};
16
17static struct comm_strs {
18 struct rw_semaphore lock;
19 struct comm_str **strs;
20 int num_strs;
21 int capacity;
22} _comm_strs;
23
24static void comm_strs__remove_if_last(struct comm_str *cs);
25
26static void comm_strs__init(void)
27 NO_THREAD_SAFETY_ANALYSIS /* Inherently single threaded due to pthread_once. */
28{
29 init_rwsem(&_comm_strs.lock);
30 _comm_strs.capacity = 16;
31 _comm_strs.num_strs = 0;
32 _comm_strs.strs = calloc(16, sizeof(*_comm_strs.strs));
33}
34
35static struct comm_strs *comm_strs__get(void)
36{
37 static pthread_once_t comm_strs_type_once = PTHREAD_ONCE_INIT;
38
39 pthread_once(&comm_strs_type_once, comm_strs__init);
40
41 return &_comm_strs;
42}
43
44static refcount_t *comm_str__refcnt(struct comm_str *cs)
45{
46 return &RC_CHK_ACCESS(cs)->refcnt;
47}
48
49static const char *comm_str__str(const struct comm_str *cs)
50{
51 return &RC_CHK_ACCESS(cs)->str[0];
52}
53
54static struct comm_str *comm_str__get(struct comm_str *cs)
55{
56 struct comm_str *result;
57
58 if (RC_CHK_GET(result, cs))
59 refcount_inc_not_zero(comm_str__refcnt(cs));
60
61 return result;
62}
63
64static void comm_str__put(struct comm_str *cs)
65{
66 if (!cs)
67 return;
68
69 if (refcount_dec_and_test(comm_str__refcnt(cs))) {
70 RC_CHK_FREE(cs);
71 } else {
72 if (refcount_read(comm_str__refcnt(cs)) == 1)
73 comm_strs__remove_if_last(cs);
74
75 RC_CHK_PUT(cs);
76 }
77}
78
79static struct comm_str *comm_str__new(const char *str)
80{
81 struct comm_str *result = NULL;
82 RC_STRUCT(comm_str) *cs;
83
84 cs = malloc(sizeof(*cs) + strlen(str) + 1);
85 if (ADD_RC_CHK(result, cs)) {
86 refcount_set(comm_str__refcnt(result), 1);
87 strcpy(&cs->str[0], str);
88 }
89 return result;
90}
91
92static int comm_str__search(const void *_key, const void *_member)
93{
94 const char *key = _key;
95 const struct comm_str *member = *(const struct comm_str * const *)_member;
96
97 return strcmp(key, comm_str__str(member));
98}
99
100static void comm_strs__remove_if_last(struct comm_str *cs)
101{
102 struct comm_strs *comm_strs = comm_strs__get();
103
104 down_write(&comm_strs->lock);
105 /*
106 * Are there only references from the array, if so remove the array
107 * reference under the write lock so that we don't race with findnew.
108 */
109 if (refcount_read(comm_str__refcnt(cs)) == 1) {
110 struct comm_str **entry;
111
112 entry = bsearch(comm_str__str(cs), comm_strs->strs, comm_strs->num_strs,
113 sizeof(struct comm_str *), comm_str__search);
114 comm_str__put(*entry);
115 for (int i = entry - comm_strs->strs; i < comm_strs->num_strs - 1; i++)
116 comm_strs->strs[i] = comm_strs->strs[i + 1];
117 comm_strs->num_strs--;
118 }
119 up_write(&comm_strs->lock);
120}
121
122static struct comm_str *__comm_strs__find(struct comm_strs *comm_strs, const char *str)
123 SHARED_LOCKS_REQUIRED(comm_strs->lock)
124{
125 struct comm_str **result;
126
127 result = bsearch(str, comm_strs->strs, comm_strs->num_strs, sizeof(struct comm_str *),
128 comm_str__search);
129
130 if (!result)
131 return NULL;
132
133 return comm_str__get(*result);
134}
135
136static struct comm_str *comm_strs__findnew(const char *str)
137{
138 struct comm_strs *comm_strs = comm_strs__get();
139 struct comm_str *result;
140
141 if (!comm_strs)
142 return NULL;
143
144 down_read(&comm_strs->lock);
145 result = __comm_strs__find(comm_strs, str);
146 up_read(&comm_strs->lock);
147 if (result)
148 return result;
149
150 down_write(&comm_strs->lock);
151 result = __comm_strs__find(comm_strs, str);
152 if (!result) {
153 if (comm_strs->num_strs == comm_strs->capacity) {
154 struct comm_str **tmp;
155
156 tmp = reallocarray(comm_strs->strs,
157 comm_strs->capacity + 16,
158 sizeof(*comm_strs->strs));
159 if (!tmp) {
160 up_write(&comm_strs->lock);
161 return NULL;
162 }
163 comm_strs->strs = tmp;
164 comm_strs->capacity += 16;
165 }
166 result = comm_str__new(str);
167 if (result) {
168 int low = 0, high = comm_strs->num_strs - 1;
169 int insert = comm_strs->num_strs; /* Default to inserting at the end. */
170
171 while (low <= high) {
172 int mid = low + (high - low) / 2;
173 int cmp = strcmp(comm_str__str(comm_strs->strs[mid]), str);
174
175 if (cmp < 0) {
176 low = mid + 1;
177 } else {
178 high = mid - 1;
179 insert = mid;
180 }
181 }
182 memmove(&comm_strs->strs[insert + 1], &comm_strs->strs[insert],
183 (comm_strs->num_strs - insert) * sizeof(struct comm_str *));
184 comm_strs->num_strs++;
185 comm_strs->strs[insert] = result;
186 }
187 }
188 up_write(&comm_strs->lock);
189 return comm_str__get(result);
190}
191
192struct comm *comm__new(const char *str, u64 timestamp, bool exec)
193{
194 struct comm *comm = zalloc(sizeof(*comm));
195
196 if (!comm)
197 return NULL;
198
199 comm->start = timestamp;
200 comm->exec = exec;
201
202 comm->comm_str = comm_strs__findnew(str);
203 if (!comm->comm_str) {
204 free(comm);
205 return NULL;
206 }
207
208 return comm;
209}
210
211int comm__override(struct comm *comm, const char *str, u64 timestamp, bool exec)
212{
213 struct comm_str *new, *old = comm->comm_str;
214
215 new = comm_strs__findnew(str);
216 if (!new)
217 return -ENOMEM;
218
219 comm_str__put(old);
220 comm->comm_str = new;
221 comm->start = timestamp;
222 if (exec)
223 comm->exec = true;
224
225 return 0;
226}
227
228void comm__free(struct comm *comm)
229{
230 comm_str__put(comm->comm_str);
231 free(comm);
232}
233
234const char *comm__str(const struct comm *comm)
235{
236 return comm_str__str(comm->comm_str);
237}