1 /* Copyright (C) 2002-2023 Free Software Foundation, Inc.
2 Contributed by Zack Weinberg <zack@codesourcery.com>
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 Under Section 7 of GPL version 3, you are granted additional
17 permissions described in the GCC Runtime Library Exception, version
18 3.1, as published by the Free Software Foundation.
19
20 You should have received a copy of the GNU General Public License and
21 a copy of the GCC Runtime Library Exception along with this program;
22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 <http://www.gnu.org/licenses/>. */
24
25 /* Threads compatibility routines for libgcc2 for VxWorks.
26 These are out-of-line routines called from gthr-vxworks.h.
27
28 This file provides the TLS related support routines, calling specific
29 VxWorks kernel entry points for this purpose. */
30
31 #include "tconfig.h"
32 #include "tsystem.h"
33 #include "gthr.h"
34
35 #if defined(__GTHREADS)
36
37 #include <vxWorks.h>
38 #ifndef __RTP__
39 #include <vxLib.h>
40 #endif
41 #include <taskLib.h>
42 #ifndef __RTP__
43 #include <taskHookLib.h>
44 #else
45 #include <errno.h>
46 #endif
47
48 #include <_vxworks-versions.h>
49
50 /* Thread-local storage.
51
52 A gthread TLS key is simply an offset in an array, the address of which
53 we store in a single pointer field associated with the current task.
54
55 On VxWorks 7, we have direct support for __thread variables and use
56 such a variable as the pointer "field". On other versions, we resort
57 to __gthread_get_tls_data and __gthread_set_tls_data functions provided
58 by the kernel.
59
60 There is also a global array which records which keys are valid and
61 which have destructors.
62
63 A task delete hook is installed to execute key destructors. The routines
64 __gthread_enter_tls_dtor_context and __gthread_leave_tls_dtor_context,
65 which are also provided by the kernel, ensure that it is safe to call
66 free() on memory allocated by the task being deleted. This is a no-op on
67 VxWorks 5, but a major undertaking on AE.
68
69 The task delete hook is only installed when at least one thread
70 has TLS data. This is a necessary precaution, to allow this module
71 to be unloaded - a module with a hook can not be removed.
72
73 Since this interface is used to allocate only a small number of
74 keys, the table size is small and static, which simplifies the
75 code quite a bit. Revisit this if and when it becomes necessary. */
76
77 #define MAX_KEYS 4
78
79 /* This is the structure pointed to by the pointer returned
80 by __gthread_get_tls_data. */
81 struct tls_data
82 {
83 int *owner;
84 void *values[MAX_KEYS];
85 unsigned int generation[MAX_KEYS];
86 };
87
88 /* To make sure we only delete TLS data associated with this object,
89 include a pointer to a local variable in the TLS data object. */
90 static int self_owner;
91
92 /* Flag to check whether the delete hook is installed. Once installed
93 it is only removed when unloading this module. */
94 static volatile int delete_hook_installed;
95
96 /* TLS data access internal API. A straight __thread variable starting with
97 VxWorks 7, a pointer returned by kernel provided routines otherwise. And
98 on VxWorks 6, the kernel expects us to notify entry/exit of regions
99 handling such variables by calls to kernel provided __gthread routines. */
100
101 #if _VXWORKS_MAJOR_GE(7)
102
103 static __thread struct tls_data *__gthread_tls_data;
104
105 #define VX_GET_TLS_DATA() __gthread_tls_data
106 #define VX_SET_TLS_DATA(x) __gthread_tls_data = (x)
107
108 #else
109
110 extern void *__gthread_get_tls_data (void);
111 extern void __gthread_set_tls_data (void *data);
112
113 #define VX_GET_TLS_DATA() __gthread_get_tls_data()
114 #define VX_SET_TLS_DATA(x) __gthread_set_tls_data(x)
115
116 #endif
117
118 #if _VXWORKS_MAJOR_EQ(6)
119
120 extern void __gthread_enter_tls_dtor_context (void);
121 extern void __gthread_leave_tls_dtor_context (void);
122
123 #define VX_ENTER_TLS_DTOR() __gthread_enter_tls_dtor_context ()
124 #define VX_LEAVE_TLS_DTOR() __gthread_leave_tls_dtor_context ()
125
126 #else
127
128 #define VX_ENTER_TLS_DTOR()
129 #define VX_LEAVE_TLS_DTOR()
130
131 #endif
132
133 /* This is a global structure which records all of the active keys.
134
135 A key is potentially valid (i.e. has been handed out by
136 __gthread_key_create) iff its generation count in this structure is
137 even. In that case, the matching entry in the dtors array is a
138 routine to be called when a thread terminates with a valid,
139 non-NULL specific value for that key.
140
141 A key is actually valid in a thread T iff the generation count
142 stored in this structure is equal to the generation count stored in
143 T's specific-value structure. */
144
145 typedef void (*tls_dtor) (void *);
146
147 struct tls_keys
148 {
149 tls_dtor dtor[MAX_KEYS];
150 unsigned int generation[MAX_KEYS];
151 };
152
153 #define KEY_VALID_P(key) !(tls_keys.generation[key] & 1)
154
155 /* Note: if MAX_KEYS is increased, this initializer must be updated
156 to match. All the generation counts begin at 1, which means no
157 key is valid. */
158 static struct tls_keys tls_keys =
159 {
160 { NULL, NULL, NULL, NULL },
161 { 1, 1, 1, 1 }
162 };
163
164 /* This lock protects the tls_keys structure. */
165 static __gthread_mutex_t tls_lock;
166
167 static __gthread_once_t tls_init_guard = __GTHREAD_ONCE_INIT;
168
169 /* Internal routines. */
170
171 /* The task TCB has just been deleted. Call the destructor
172 function for each TLS key that has both a destructor and
173 a non-NULL specific value in this thread.
174
175 This routine does not need to take tls_lock; the generation
176 count protects us from calling a stale destructor. It does
177 need to read tls_keys.dtor[key] atomically. */
178
179 void
180 tls_delete_hook (void *tcb ATTRIBUTE_UNUSED)
181 {
182 struct tls_data *data;
183 __gthread_key_t key;
184
185 data = VX_GET_TLS_DATA();
186
187 if (data && data->owner == &self_owner)
188 {
189 VX_ENTER_TLS_DTOR();
190 for (key = 0; key < MAX_KEYS; key++)
191 {
192 if (data->generation[key] == tls_keys.generation[key])
193 {
194 tls_dtor dtor = tls_keys.dtor[key];
195
196 if (dtor)
197 dtor (data->values[key]);
198 }
199 }
200 free (data);
201
202 VX_LEAVE_TLS_DTOR();
203 VX_SET_TLS_DATA(NULL);
204 }
205 }
206
207 /* Initialize global data used by the TLS system. */
208 static void
209 tls_init (void)
210 {
211 __GTHREAD_MUTEX_INIT_FUNCTION (&tls_lock);
212 }
213
214 static void tls_destructor (void) __attribute__ ((destructor));
215 static void
216 tls_destructor (void)
217 {
218 #ifdef __RTP__
219 /* All threads but this one should have exited by now. */
220 tls_delete_hook (NULL);
221 #endif
222 /* Unregister the hook. */
223 if (delete_hook_installed)
224 taskDeleteHookDelete ((FUNCPTR)tls_delete_hook);
225
226 if (tls_init_guard.done && __gthread_mutex_lock (&tls_lock) != ERROR)
227 semDelete (tls_lock);
228 }
229
230 /* External interface */
231
232 /* Store in KEYP a value which can be passed to __gthread_setspecific/
233 __gthread_getspecific to store and retrieve a value which is
234 specific to each calling thread. If DTOR is not NULL, it will be
235 called when a thread terminates with a non-NULL specific value for
236 this key, with the value as its sole argument. */
237
238 int
239 __gthread_key_create (__gthread_key_t *keyp, tls_dtor dtor)
240 {
241 __gthread_key_t key;
242
243 __gthread_once (&tls_init_guard, tls_init);
244
245 if (__gthread_mutex_lock (&tls_lock) == ERROR)
246 return errno;
247
248 for (key = 0; key < MAX_KEYS; key++)
249 if (!KEY_VALID_P (key))
250 goto found_slot;
251
252 /* no room */
253 __gthread_mutex_unlock (&tls_lock);
254 return EAGAIN;
255
256 found_slot:
257 tls_keys.generation[key]++; /* making it even */
258 tls_keys.dtor[key] = dtor;
259 *keyp = key;
260 __gthread_mutex_unlock (&tls_lock);
261 return 0;
262 }
263
264 /* Invalidate KEY; it can no longer be used as an argument to
265 setspecific/getspecific. Note that this does NOT call destructor
266 functions for any live values for this key. */
267 int
268 __gthread_key_delete (__gthread_key_t key)
269 {
270 if (key >= MAX_KEYS)
271 return EINVAL;
272
273 __gthread_once (&tls_init_guard, tls_init);
274
275 if (__gthread_mutex_lock (&tls_lock) == ERROR)
276 return errno;
277
278 if (!KEY_VALID_P (key))
279 {
280 __gthread_mutex_unlock (&tls_lock);
281 return EINVAL;
282 }
283
284 tls_keys.generation[key]++; /* making it odd */
285 tls_keys.dtor[key] = 0;
286
287 __gthread_mutex_unlock (&tls_lock);
288 return 0;
289 }
290
291 /* Retrieve the thread-specific value for KEY. If it has never been
292 set in this thread, or KEY is invalid, returns NULL.
293
294 It does not matter if this function races with key_create or
295 key_delete; the worst that can happen is you get a value other than
296 the one that a serialized implementation would have provided. */
297
298 void *
299 __gthread_getspecific (__gthread_key_t key)
300 {
301 struct tls_data *data;
302
303 if (key >= MAX_KEYS)
304 return 0;
305
306 data = VX_GET_TLS_DATA();
307
308 if (!data)
309 return 0;
310
311 if (data->generation[key] != tls_keys.generation[key])
312 return 0;
313
314 return data->values[key];
315 }
316
317 /* Set the thread-specific value for KEY. If KEY is invalid, or
318 memory allocation fails, returns -1, otherwise 0.
319
320 The generation count protects this function against races with
321 key_create/key_delete; the worst thing that can happen is that a
322 value is successfully stored into a dead generation (and then
323 immediately becomes invalid). However, we do have to make sure
324 to read tls_keys.generation[key] atomically. */
325
326 int
327 __gthread_setspecific (__gthread_key_t key, void *value)
328 {
329 struct tls_data *data;
330 unsigned int generation;
331
332 if (key >= MAX_KEYS)
333 return EINVAL;
334
335 data = VX_GET_TLS_DATA();
336
337 if (!data)
338 {
339 if (!delete_hook_installed)
340 {
341 /* Install the delete hook. */
342 if (__gthread_mutex_lock (&tls_lock) == ERROR)
343 return ENOMEM;
344 if (!delete_hook_installed)
345 {
346 taskDeleteHookAdd ((FUNCPTR)tls_delete_hook);
347 delete_hook_installed = 1;
348 }
349 __gthread_mutex_unlock (&tls_lock);
350 }
351
352 data = malloc (sizeof (struct tls_data));
353 if (!data)
354 return ENOMEM;
355
356 memset (data, 0, sizeof (struct tls_data));
357 data->owner = &self_owner;
358
359 VX_SET_TLS_DATA(data);
360 }
361
362 generation = tls_keys.generation[key];
363
364 if (generation & 1)
365 return EINVAL;
366
367 data->generation[key] = generation;
368 data->values[key] = value;
369
370 return 0;
371 }
372 #endif /* __GTHREADS */