No issues found
1 /* Thread package.
2 This is intended to be usable independently from Python.
3 The implementation for system foobar is in a file thread_foobar.h
4 which is included by this file dependent on config settings.
5 Stuff shared by all thread_*.h files is collected here. */
6
7 #include "Python.h"
8
9
10 #ifndef _POSIX_THREADS
11 /* This means pthreads are not implemented in libc headers, hence the macro
12 not present in unistd.h. But they still can be implemented as an external
13 library (e.g. gnu pth in pthread emulation) */
14 # ifdef HAVE_PTHREAD_H
15 # include <pthread.h> /* _POSIX_THREADS */
16 # endif
17 #endif
18
19 #ifndef DONT_HAVE_STDIO_H
20 #include <stdio.h>
21 #endif
22
23 #include <stdlib.h>
24
25 #ifdef __sgi
26 #ifndef HAVE_PTHREAD_H /* XXX Need to check in configure.in */
27 #undef _POSIX_THREADS
28 #endif
29 #endif
30
31 #include "pythread.h"
32
33 #ifndef _POSIX_THREADS
34
35 #ifdef __sgi
36 #define SGI_THREADS
37 #endif
38
39 #ifdef HAVE_THREAD_H
40 #define SOLARIS_THREADS
41 #endif
42
43 #if defined(sun) && !defined(SOLARIS_THREADS)
44 #define SUN_LWP
45 #endif
46
47 /* Check if we're running on HP-UX and _SC_THREADS is defined. If so, then
48 enough of the Posix threads package is implemented to support python
49 threads.
50
51 This is valid for HP-UX 11.23 running on an ia64 system. If needed, add
52 a check of __ia64 to verify that we're running on a ia64 system instead
53 of a pa-risc system.
54 */
55 #ifdef __hpux
56 #ifdef _SC_THREADS
57 #define _POSIX_THREADS
58 #endif
59 #endif
60
61 #endif /* _POSIX_THREADS */
62
63
64 #ifdef Py_DEBUG
65 static int thread_debug = 0;
66 #define dprintf(args) (void)((thread_debug & 1) && printf args)
67 #define d2printf(args) ((thread_debug & 8) && printf args)
68 #else
69 #define dprintf(args)
70 #define d2printf(args)
71 #endif
72
73 static int initialized;
74
75 static void PyThread__init_thread(void); /* Forward */
76
77 void
78 PyThread_init_thread(void)
79 {
80 #ifdef Py_DEBUG
81 char *p = Py_GETENV("PYTHONTHREADDEBUG");
82
83 if (p) {
84 if (*p)
85 thread_debug = atoi(p);
86 else
87 thread_debug = 1;
88 }
89 #endif /* Py_DEBUG */
90 if (initialized)
91 return;
92 initialized = 1;
93 dprintf(("PyThread_init_thread called\n"));
94 PyThread__init_thread();
95 }
96
97 /* Support for runtime thread stack size tuning.
98 A value of 0 means using the platform's default stack size
99 or the size specified by the THREAD_STACK_SIZE macro. */
100 static size_t _pythread_stacksize = 0;
101
102 #ifdef SGI_THREADS
103 #include "thread_sgi.h"
104 #endif
105
106 #ifdef SOLARIS_THREADS
107 #include "thread_solaris.h"
108 #endif
109
110 #ifdef SUN_LWP
111 #include "thread_lwp.h"
112 #endif
113
114 #ifdef HAVE_PTH
115 #include "thread_pth.h"
116 #undef _POSIX_THREADS
117 #endif
118
119 #ifdef _POSIX_THREADS
120 #include "thread_pthread.h"
121 #endif
122
123 #ifdef C_THREADS
124 #include "thread_cthread.h"
125 #endif
126
127 #ifdef NT_THREADS
128 #include "thread_nt.h"
129 #endif
130
131 #ifdef OS2_THREADS
132 #include "thread_os2.h"
133 #endif
134
135 #ifdef BEOS_THREADS
136 #include "thread_beos.h"
137 #endif
138
139 #ifdef PLAN9_THREADS
140 #include "thread_plan9.h"
141 #endif
142
143 #ifdef ATHEOS_THREADS
144 #include "thread_atheos.h"
145 #endif
146
147 /*
148 #ifdef FOOBAR_THREADS
149 #include "thread_foobar.h"
150 #endif
151 */
152
153 /* return the current thread stack size */
154 size_t
155 PyThread_get_stacksize(void)
156 {
157 return _pythread_stacksize;
158 }
159
160 /* Only platforms defining a THREAD_SET_STACKSIZE() macro
161 in thread_<platform>.h support changing the stack size.
162 Return 0 if stack size is valid,
163 -1 if stack size value is invalid,
164 -2 if setting stack size is not supported. */
165 int
166 PyThread_set_stacksize(size_t size)
167 {
168 #if defined(THREAD_SET_STACKSIZE)
169 return THREAD_SET_STACKSIZE(size);
170 #else
171 return -2;
172 #endif
173 }
174
175 #ifndef Py_HAVE_NATIVE_TLS
176 /* If the platform has not supplied a platform specific
177 TLS implementation, provide our own.
178
179 This code stolen from "thread_sgi.h", where it was the only
180 implementation of an existing Python TLS API.
181 */
182 /* ------------------------------------------------------------------------
183 Per-thread data ("key") support.
184
185 Use PyThread_create_key() to create a new key. This is typically shared
186 across threads.
187
188 Use PyThread_set_key_value(thekey, value) to associate void* value with
189 thekey in the current thread. Each thread has a distinct mapping of thekey
190 to a void* value. Caution: if the current thread already has a mapping
191 for thekey, value is ignored.
192
193 Use PyThread_get_key_value(thekey) to retrieve the void* value associated
194 with thekey in the current thread. This returns NULL if no value is
195 associated with thekey in the current thread.
196
197 Use PyThread_delete_key_value(thekey) to forget the current thread's associated
198 value for thekey. PyThread_delete_key(thekey) forgets the values associated
199 with thekey across *all* threads.
200
201 While some of these functions have error-return values, none set any
202 Python exception.
203
204 None of the functions does memory management on behalf of the void* values.
205 You need to allocate and deallocate them yourself. If the void* values
206 happen to be PyObject*, these functions don't do refcount operations on
207 them either.
208
209 The GIL does not need to be held when calling these functions; they supply
210 their own locking. This isn't true of PyThread_create_key(), though (see
211 next paragraph).
212
213 There's a hidden assumption that PyThread_create_key() will be called before
214 any of the other functions are called. There's also a hidden assumption
215 that calls to PyThread_create_key() are serialized externally.
216 ------------------------------------------------------------------------ */
217
218 /* A singly-linked list of struct key objects remembers all the key->value
219 * associations. File static keyhead heads the list. keymutex is used
220 * to enforce exclusion internally.
221 */
222 struct key {
223 /* Next record in the list, or NULL if this is the last record. */
224 struct key *next;
225
226 /* The thread id, according to PyThread_get_thread_ident(). */
227 long id;
228
229 /* The key and its associated value. */
230 int key;
231 void *value;
232 };
233
234 static struct key *keyhead = NULL;
235 static PyThread_type_lock keymutex = NULL;
236 static int nkeys = 0; /* PyThread_create_key() hands out nkeys+1 next */
237
238 /* Internal helper.
239 * If the current thread has a mapping for key, the appropriate struct key*
240 * is returned. NB: value is ignored in this case!
241 * If there is no mapping for key in the current thread, then:
242 * If value is NULL, NULL is returned.
243 * Else a mapping of key to value is created for the current thread,
244 * and a pointer to a new struct key* is returned; except that if
245 * malloc() can't find room for a new struct key*, NULL is returned.
246 * So when value==NULL, this acts like a pure lookup routine, and when
247 * value!=NULL, this acts like dict.setdefault(), returning an existing
248 * mapping if one exists, else creating a new mapping.
249 *
250 * Caution: this used to be too clever, trying to hold keymutex only
251 * around the "p->next = keyhead; keyhead = p" pair. That allowed
252 * another thread to mutate the list, via key deletion, concurrent with
253 * find_key() crawling over the list. Hilarity ensued. For example, when
254 * the for-loop here does "p = p->next", p could end up pointing at a
255 * record that PyThread_delete_key_value() was concurrently free()'ing.
256 * That could lead to anything, from failing to find a key that exists, to
257 * segfaults. Now we lock the whole routine.
258 */
259 static struct key *
260 find_key(int key, void *value)
261 {
262 struct key *p, *prev_p;
263 long id = PyThread_get_thread_ident();
264
265 if (!keymutex)
266 return NULL;
267 PyThread_acquire_lock(keymutex, 1);
268 prev_p = NULL;
269 for (p = keyhead; p != NULL; p = p->next) {
270 if (p->id == id && p->key == key)
271 goto Done;
272 /* Sanity check. These states should never happen but if
273 * they do we must abort. Otherwise we'll end up spinning in
274 * in a tight loop with the lock held. A similar check is done
275 * in pystate.c tstate_delete_common(). */
276 if (p == prev_p)
277 Py_FatalError("tls find_key: small circular list(!)");
278 prev_p = p;
279 if (p->next == keyhead)
280 Py_FatalError("tls find_key: circular list(!)");
281 }
282 if (value == NULL) {
283 assert(p == NULL);
284 goto Done;
285 }
286 p = (struct key *)malloc(sizeof(struct key));
287 if (p != NULL) {
288 p->id = id;
289 p->key = key;
290 p->value = value;
291 p->next = keyhead;
292 keyhead = p;
293 }
294 Done:
295 PyThread_release_lock(keymutex);
296 return p;
297 }
298
299 /* Return a new key. This must be called before any other functions in
300 * this family, and callers must arrange to serialize calls to this
301 * function. No violations are detected.
302 */
303 int
304 PyThread_create_key(void)
305 {
306 /* All parts of this function are wrong if it's called by multiple
307 * threads simultaneously.
308 */
309 if (keymutex == NULL)
310 keymutex = PyThread_allocate_lock();
311 return ++nkeys;
312 }
313
314 /* Forget the associations for key across *all* threads. */
315 void
316 PyThread_delete_key(int key)
317 {
318 struct key *p, **q;
319
320 PyThread_acquire_lock(keymutex, 1);
321 q = &keyhead;
322 while ((p = *q) != NULL) {
323 if (p->key == key) {
324 *q = p->next;
325 free((void *)p);
326 /* NB This does *not* free p->value! */
327 }
328 else
329 q = &p->next;
330 }
331 PyThread_release_lock(keymutex);
332 }
333
334 /* Confusing: If the current thread has an association for key,
335 * value is ignored, and 0 is returned. Else an attempt is made to create
336 * an association of key to value for the current thread. 0 is returned
337 * if that succeeds, but -1 is returned if there's not enough memory
338 * to create the association. value must not be NULL.
339 */
340 int
341 PyThread_set_key_value(int key, void *value)
342 {
343 struct key *p;
344
345 assert(value != NULL);
346 p = find_key(key, value);
347 if (p == NULL)
348 return -1;
349 else
350 return 0;
351 }
352
353 /* Retrieve the value associated with key in the current thread, or NULL
354 * if the current thread doesn't have an association for key.
355 */
356 void *
357 PyThread_get_key_value(int key)
358 {
359 struct key *p = find_key(key, NULL);
360
361 if (p == NULL)
362 return NULL;
363 else
364 return p->value;
365 }
366
367 /* Forget the current thread's association for key, if any. */
368 void
369 PyThread_delete_key_value(int key)
370 {
371 long id = PyThread_get_thread_ident();
372 struct key *p, **q;
373
374 PyThread_acquire_lock(keymutex, 1);
375 q = &keyhead;
376 while ((p = *q) != NULL) {
377 if (p->key == key && p->id == id) {
378 *q = p->next;
379 free((void *)p);
380 /* NB This does *not* free p->value! */
381 break;
382 }
383 else
384 q = &p->next;
385 }
386 PyThread_release_lock(keymutex);
387 }
388
389 /* Forget everything not associated with the current thread id.
390 * This function is called from PyOS_AfterFork(). It is necessary
391 * because other thread ids which were in use at the time of the fork
392 * may be reused for new threads created in the forked process.
393 */
394 void
395 PyThread_ReInitTLS(void)
396 {
397 long id = PyThread_get_thread_ident();
398 struct key *p, **q;
399
400 if (!keymutex)
401 return;
402
403 /* As with interpreter_lock in PyEval_ReInitThreads()
404 we just create a new lock without freeing the old one */
405 keymutex = PyThread_allocate_lock();
406
407 /* Delete all keys which do not match the current thread id */
408 q = &keyhead;
409 while ((p = *q) != NULL) {
410 if (p->id != id) {
411 *q = p->next;
412 free((void *)p);
413 /* NB This does *not* free p->value! */
414 }
415 else
416 q = &p->next;
417 }
418 }
419
420 #endif /* Py_HAVE_NATIVE_TLS */