1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
2 /* threads for Linux.                                                   */
3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
4 /*                                                                      */
5 /* This program is free software; you can redistribute it and/or        */
6 /* modify it under the terms of the GNU Library General Public License  */
7 /* as published by the Free Software Foundation; either version 2       */
8 /* of the License, or (at your option) any later version.               */
9 /*                                                                      */
10 /* This program is distributed in the hope that it will be useful,      */
11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
13 /* GNU Library General Public License for more details.                 */
14 
15 /* Mutexes */
16 
17 #include <errno.h>
18 #include <sched.h>
19 #include <stddef.h>
20 #include <limits.h>
21 #include "pthread.h"
22 #include "internals.h"
23 #include "spinlock.h"
24 #include "queue.h"
25 #include "restart.h"
26 
__pthread_mutex_init(pthread_mutex_t * mutex,const pthread_mutexattr_t * mutex_attr)27 int attribute_hidden __pthread_mutex_init(pthread_mutex_t * mutex,
28                        const pthread_mutexattr_t * mutex_attr)
29 {
30   __pthread_init_lock(&mutex->__m_lock);
31   mutex->__m_kind =
32     mutex_attr == NULL ? PTHREAD_MUTEX_TIMED_NP : mutex_attr->__mutexkind;
33   mutex->__m_count = 0;
34   mutex->__m_owner = NULL;
35   return 0;
36 }
strong_alias(__pthread_mutex_init,pthread_mutex_init)37 strong_alias (__pthread_mutex_init, pthread_mutex_init)
38 
39 int attribute_hidden __pthread_mutex_destroy(pthread_mutex_t * mutex)
40 {
41   switch (mutex->__m_kind) {
42   case PTHREAD_MUTEX_ADAPTIVE_NP:
43   case PTHREAD_MUTEX_RECURSIVE_NP:
44     if ((mutex->__m_lock.__status & 1) != 0)
45       return EBUSY;
46     return 0;
47   case PTHREAD_MUTEX_ERRORCHECK_NP:
48   case PTHREAD_MUTEX_TIMED_NP:
49     if (mutex->__m_lock.__status != 0)
50       return EBUSY;
51     return 0;
52   default:
53     return EINVAL;
54   }
55 }
strong_alias(__pthread_mutex_destroy,pthread_mutex_destroy)56 strong_alias (__pthread_mutex_destroy, pthread_mutex_destroy)
57 
58 int attribute_hidden __pthread_mutex_trylock(pthread_mutex_t * mutex)
59 {
60   pthread_descr self;
61   int retcode;
62 
63   switch(mutex->__m_kind) {
64   case PTHREAD_MUTEX_ADAPTIVE_NP:
65     retcode = __pthread_trylock(&mutex->__m_lock);
66     return retcode;
67   case PTHREAD_MUTEX_RECURSIVE_NP:
68     self = thread_self();
69     if (mutex->__m_owner == self) {
70       mutex->__m_count++;
71       return 0;
72     }
73     retcode = __pthread_trylock(&mutex->__m_lock);
74     if (retcode == 0) {
75       mutex->__m_owner = self;
76       mutex->__m_count = 0;
77     }
78     return retcode;
79   case PTHREAD_MUTEX_ERRORCHECK_NP:
80     retcode = __pthread_alt_trylock(&mutex->__m_lock);
81     if (retcode == 0) {
82       mutex->__m_owner = thread_self();
83     }
84     return retcode;
85   case PTHREAD_MUTEX_TIMED_NP:
86     retcode = __pthread_alt_trylock(&mutex->__m_lock);
87     return retcode;
88   default:
89     return EINVAL;
90   }
91 }
strong_alias(__pthread_mutex_trylock,pthread_mutex_trylock)92 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
93 
94 int attribute_hidden __pthread_mutex_lock(pthread_mutex_t * mutex)
95 {
96   pthread_descr self;
97 
98   switch(mutex->__m_kind) {
99   case PTHREAD_MUTEX_ADAPTIVE_NP:
100     __pthread_lock(&mutex->__m_lock, NULL);
101     return 0;
102   case PTHREAD_MUTEX_RECURSIVE_NP:
103     self = thread_self();
104     if (mutex->__m_owner == self) {
105       mutex->__m_count++;
106       return 0;
107     }
108     __pthread_lock(&mutex->__m_lock, self);
109     mutex->__m_owner = self;
110     mutex->__m_count = 0;
111     return 0;
112   case PTHREAD_MUTEX_ERRORCHECK_NP:
113     self = thread_self();
114     if (mutex->__m_owner == self) return EDEADLK;
115     __pthread_alt_lock(&mutex->__m_lock, self);
116     mutex->__m_owner = self;
117     return 0;
118   case PTHREAD_MUTEX_TIMED_NP:
119     __pthread_alt_lock(&mutex->__m_lock, NULL);
120     return 0;
121   default:
122     return EINVAL;
123   }
124 }
strong_alias(__pthread_mutex_lock,pthread_mutex_lock)125 strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
126 
127 int pthread_mutex_timedlock (pthread_mutex_t *mutex,
128 			       const struct timespec *abstime)
129 {
130   pthread_descr self;
131   int res;
132 
133   if (__builtin_expect (abstime->tv_nsec, 0) < 0
134       || __builtin_expect (abstime->tv_nsec, 0) >= 1000000000)
135     return EINVAL;
136 
137   switch(mutex->__m_kind) {
138   case PTHREAD_MUTEX_ADAPTIVE_NP:
139     __pthread_lock(&mutex->__m_lock, NULL);
140     return 0;
141   case PTHREAD_MUTEX_RECURSIVE_NP:
142     self = thread_self();
143     if (mutex->__m_owner == self) {
144       mutex->__m_count++;
145       return 0;
146     }
147     __pthread_lock(&mutex->__m_lock, self);
148     mutex->__m_owner = self;
149     mutex->__m_count = 0;
150     return 0;
151   case PTHREAD_MUTEX_ERRORCHECK_NP:
152     self = thread_self();
153     if (mutex->__m_owner == self) return EDEADLK;
154     res = __pthread_alt_timedlock(&mutex->__m_lock, self, abstime);
155     if (res != 0)
156       {
157 	mutex->__m_owner = self;
158 	return 0;
159       }
160     return ETIMEDOUT;
161   case PTHREAD_MUTEX_TIMED_NP:
162     /* Only this type supports timed out lock. */
163     return (__pthread_alt_timedlock(&mutex->__m_lock, NULL, abstime)
164 	    ? 0 : ETIMEDOUT);
165   default:
166     return EINVAL;
167   }
168 }
169 
__pthread_mutex_unlock(pthread_mutex_t * mutex)170 int attribute_hidden __pthread_mutex_unlock(pthread_mutex_t * mutex)
171 {
172   switch (mutex->__m_kind) {
173   case PTHREAD_MUTEX_ADAPTIVE_NP:
174     __pthread_unlock(&mutex->__m_lock);
175     return 0;
176   case PTHREAD_MUTEX_RECURSIVE_NP:
177     if (mutex->__m_owner != thread_self())
178       return EPERM;
179     if (mutex->__m_count > 0) {
180       mutex->__m_count--;
181       return 0;
182     }
183     mutex->__m_owner = NULL;
184     __pthread_unlock(&mutex->__m_lock);
185     return 0;
186   case PTHREAD_MUTEX_ERRORCHECK_NP:
187     if (mutex->__m_owner != thread_self() || mutex->__m_lock.__status == 0)
188       return EPERM;
189     mutex->__m_owner = NULL;
190     __pthread_alt_unlock(&mutex->__m_lock);
191     return 0;
192   case PTHREAD_MUTEX_TIMED_NP:
193     __pthread_alt_unlock(&mutex->__m_lock);
194     return 0;
195   default:
196     return EINVAL;
197   }
198 }
strong_alias(__pthread_mutex_unlock,pthread_mutex_unlock)199 strong_alias (__pthread_mutex_unlock, pthread_mutex_unlock)
200 
201 int attribute_hidden __pthread_mutexattr_init(pthread_mutexattr_t *attr)
202 {
203   attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
204   return 0;
205 }
strong_alias(__pthread_mutexattr_init,pthread_mutexattr_init)206 strong_alias(__pthread_mutexattr_init,pthread_mutexattr_init)
207 
208 int attribute_hidden __pthread_mutexattr_destroy(pthread_mutexattr_t *attr attribute_unused)
209 {
210   return 0;
211 }
strong_alias(__pthread_mutexattr_destroy,pthread_mutexattr_destroy)212 strong_alias(__pthread_mutexattr_destroy,pthread_mutexattr_destroy)
213 
214 int attribute_hidden __pthread_mutexattr_settype(pthread_mutexattr_t *attr, int kind)
215 {
216   if (kind != PTHREAD_MUTEX_ADAPTIVE_NP
217       && kind != PTHREAD_MUTEX_RECURSIVE_NP
218       && kind != PTHREAD_MUTEX_ERRORCHECK_NP
219       && kind != PTHREAD_MUTEX_TIMED_NP)
220     return EINVAL;
221   attr->__mutexkind = kind;
222   return 0;
223 }
224 strong_alias(__pthread_mutexattr_settype,pthread_mutexattr_settype)
225 strong_alias (__pthread_mutexattr_settype, __pthread_mutexattr_setkind_np)
226 weak_alias (__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np)
227 
228 int __pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *kind) attribute_hidden;
__pthread_mutexattr_gettype(const pthread_mutexattr_t * attr,int * kind)229 int __pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *kind)
230 {
231   *kind = attr->__mutexkind;
232   return 0;
233 }
234 weak_alias (__pthread_mutexattr_gettype, pthread_mutexattr_gettype)
235 strong_alias (__pthread_mutexattr_gettype, __pthread_mutexattr_getkind_np)
236 weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
237 
238 int __pthread_mutexattr_getpshared (const pthread_mutexattr_t *attr attribute_unused,
239 				   int *pshared) attribute_hidden;
__pthread_mutexattr_getpshared(const pthread_mutexattr_t * attr attribute_unused,int * pshared)240 int __pthread_mutexattr_getpshared (const pthread_mutexattr_t *attr attribute_unused,
241 				   int *pshared)
242 {
243   *pshared = PTHREAD_PROCESS_PRIVATE;
244   return 0;
245 }
246 weak_alias (__pthread_mutexattr_getpshared, pthread_mutexattr_getpshared)
247 
248 int __pthread_mutexattr_setpshared (pthread_mutexattr_t *attr attribute_unused, int pshared) attribute_hidden;
__pthread_mutexattr_setpshared(pthread_mutexattr_t * attr attribute_unused,int pshared)249 int __pthread_mutexattr_setpshared (pthread_mutexattr_t *attr attribute_unused, int pshared)
250 {
251   if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)
252     return EINVAL;
253 
254   /* For now it is not possible to shared a conditional variable.  */
255   if (pshared != PTHREAD_PROCESS_PRIVATE)
256     return ENOSYS;
257 
258   return 0;
259 }
260 weak_alias (__pthread_mutexattr_setpshared, pthread_mutexattr_setpshared)
261 
262 /* Once-only execution */
263 
264 static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
265 static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
266 static int fork_generation = 0;	/* Child process increments this after fork. */
267 
268 enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
269 
270 /* If a thread is canceled while calling the init_routine out of
271    pthread once, this handler will reset the once_control variable
272    to the NEVER state. */
273 
pthread_once_cancelhandler(void * arg)274 static void pthread_once_cancelhandler(void *arg)
275 {
276     pthread_once_t *once_control = arg;
277 
278     __pthread_mutex_lock(&once_masterlock);
279     *once_control = NEVER;
280     __pthread_mutex_unlock(&once_masterlock);
281     pthread_cond_broadcast(&once_finished);
282 }
283 
__pthread_once(pthread_once_t * once_control,void (* init_routine)(void))284 int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
285 {
286   /* flag for doing the condition broadcast outside of mutex */
287   int state_changed;
288 
289   /* Test without locking first for speed */
290   if (*once_control == DONE) {
291     READ_MEMORY_BARRIER();
292     return 0;
293   }
294   /* Lock and test again */
295 
296   state_changed = 0;
297 
298   __pthread_mutex_lock(&once_masterlock);
299 
300   /* If this object was left in an IN_PROGRESS state in a parent
301      process (indicated by stale generation field), reset it to NEVER. */
302   if ((*once_control & 3) == IN_PROGRESS && (*once_control & ~3) != fork_generation)
303     *once_control = NEVER;
304 
305   /* If init_routine is being called from another routine, wait until
306      it completes. */
307   while ((*once_control & 3) == IN_PROGRESS) {
308     pthread_cond_wait(&once_finished, &once_masterlock);
309   }
310   /* Here *once_control is stable and either NEVER or DONE. */
311   if (*once_control == NEVER) {
312     *once_control = IN_PROGRESS | fork_generation;
313     __pthread_mutex_unlock(&once_masterlock);
314     pthread_cleanup_push(pthread_once_cancelhandler, once_control);
315     init_routine();
316     pthread_cleanup_pop(0);
317     __pthread_mutex_lock(&once_masterlock);
318     WRITE_MEMORY_BARRIER();
319     *once_control = DONE;
320     state_changed = 1;
321   }
322   __pthread_mutex_unlock(&once_masterlock);
323 
324   if (state_changed)
325     pthread_cond_broadcast(&once_finished);
326 
327   return 0;
328 }
329 strong_alias (__pthread_once, pthread_once)
330 
331 /*
332  * Handle the state of the pthread_once mechanism across forks.  The
333  * once_masterlock is acquired in the parent process prior to a fork to ensure
334  * that no thread is in the critical region protected by the lock.  After the
335  * fork, the lock is released. In the child, the lock and the condition
336  * variable are simply reset.  The child also increments its generation
337  * counter which lets pthread_once calls detect stale IN_PROGRESS states
338  * and reset them back to NEVER.
339  */
340 
341 void __pthread_once_fork_prepare(void);
__pthread_once_fork_prepare(void)342 void __pthread_once_fork_prepare(void)
343 {
344   __pthread_mutex_lock(&once_masterlock);
345 }
346 
347 void __pthread_once_fork_parent(void);
__pthread_once_fork_parent(void)348 void __pthread_once_fork_parent(void)
349 {
350   __pthread_mutex_unlock(&once_masterlock);
351 }
352 
353 void __pthread_once_fork_child(void);
__pthread_once_fork_child(void)354 void __pthread_once_fork_child(void)
355 {
356   __pthread_mutex_init(&once_masterlock, NULL);
357   pthread_cond_init(&once_finished, NULL);
358   if (fork_generation <= INT_MAX - 4)
359     fork_generation += 4;	/* leave least significant two bits zero */
360   else
361     fork_generation = 0;
362 }
363