1/* Private libc-internal interface for mutex locks. NPTL version.
2 Copyright (C) 1996-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation; either version 2.1 of the
8 License, or (at your option) any later version.
9
10 The GNU C Library 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 GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; see the file COPYING.LIB. If
17 not, see <https://www.gnu.org/licenses/>. */
18
19#ifndef _LIBC_LOCKP_H
20#define _LIBC_LOCKP_H 1
21
22#include <pthread.h>
23#define __need_NULL
24#include <stddef.h>
25
26
27/* Fortunately Linux now has a mean to do locking which is realtime
28 safe without the aid of the thread library. We also need no fancy
29 options like error checking mutexes etc. We only need simple
30 locks, maybe recursive. This can be easily and cheaply implemented
31 using futexes. We will use them everywhere except in ld.so since
32 ld.so might be used on old kernels with a different libc.so. */
33#include <lowlevellock.h>
34#include <tls.h>
35#include <pthread-functions.h>
36
37#if IS_IN (libpthread)
38/* This gets us the declarations of the __pthread_* internal names,
39 and hidden_proto for them. */
40# include <nptl/pthreadP.h>
41#endif
42
43/* Mutex type. */
44#if !IS_IN (libc) && !IS_IN (libpthread)
45typedef pthread_mutex_t __libc_lock_t;
46#else
47typedef int __libc_lock_t;
48#endif
49typedef struct { pthread_mutex_t mutex; } __rtld_lock_recursive_t;
50typedef pthread_rwlock_t __libc_rwlock_t;
51
52/* Type for key to thread-specific data. */
53typedef pthread_key_t __libc_key_t;
54
55/* Define a lock variable NAME with storage class CLASS. The lock must be
56 initialized with __libc_lock_init before it can be used (or define it
57 with __libc_lock_define_initialized, below). Use `extern' for CLASS to
58 declare a lock defined in another module. In public structure
59 definitions you must use a pointer to the lock structure (i.e., NAME
60 begins with a `*'), because its storage size will not be known outside
61 of libc. */
62#define __libc_lock_define(CLASS,NAME) \
63 CLASS __libc_lock_t NAME;
64#define __libc_rwlock_define(CLASS,NAME) \
65 CLASS __libc_rwlock_t NAME;
66#define __rtld_lock_define_recursive(CLASS,NAME) \
67 CLASS __rtld_lock_recursive_t NAME;
68
69/* Define an initialized lock variable NAME with storage class CLASS.
70
71 For the C library we take a deeper look at the initializer. For
72 this implementation all fields are initialized to zero. Therefore
73 we don't initialize the variable which allows putting it into the
74 BSS section. */
75
76_Static_assert (LLL_LOCK_INITIALIZER == 0, "LLL_LOCK_INITIALIZER != 0");
77#define _LIBC_LOCK_INITIALIZER LLL_LOCK_INITIALIZER
78#define __libc_lock_define_initialized(CLASS,NAME) \
79 CLASS __libc_lock_t NAME;
80
81#define __libc_rwlock_define_initialized(CLASS,NAME) \
82 CLASS __libc_rwlock_t NAME = PTHREAD_RWLOCK_INITIALIZER;
83
84#define __rtld_lock_define_initialized_recursive(CLASS,NAME) \
85 CLASS __rtld_lock_recursive_t NAME = _RTLD_LOCK_RECURSIVE_INITIALIZER;
86#define _RTLD_LOCK_RECURSIVE_INITIALIZER \
87 {PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP}
88
89#define __rtld_lock_initialize(NAME) \
90 (void) ((NAME) = (__rtld_lock_recursive_t) _RTLD_LOCK_RECURSIVE_INITIALIZER)
91
92/* If we check for a weakly referenced symbol and then perform a
93 normal jump to it te code generated for some platforms in case of
94 PIC is unnecessarily slow. What would happen is that the function
95 is first referenced as data and then it is called indirectly
96 through the PLT. We can make this a direct jump. */
97#ifdef __PIC__
98# define __libc_maybe_call(FUNC, ARGS, ELSE) \
99 (__extension__ ({ __typeof (FUNC) *_fn = (FUNC); \
100 _fn != NULL ? (*_fn) ARGS : ELSE; }))
101#else
102# define __libc_maybe_call(FUNC, ARGS, ELSE) \
103 (FUNC != NULL ? FUNC ARGS : ELSE)
104#endif
105
106/* Call thread functions through the function pointer table. */
107#if defined SHARED && IS_IN (libc)
108# define PTFAVAIL(NAME) __libc_pthread_functions_init
109# define __libc_ptf_call(FUNC, ARGS, ELSE) \
110 (__libc_pthread_functions_init ? PTHFCT_CALL (ptr_##FUNC, ARGS) : ELSE)
111# define __libc_ptf_call_always(FUNC, ARGS) \
112 PTHFCT_CALL (ptr_##FUNC, ARGS)
113#elif IS_IN (libpthread)
114# define PTFAVAIL(NAME) 1
115# define __libc_ptf_call(FUNC, ARGS, ELSE) \
116 FUNC ARGS
117# define __libc_ptf_call_always(FUNC, ARGS) \
118 FUNC ARGS
119#else
120# define PTFAVAIL(NAME) (NAME != NULL)
121# define __libc_ptf_call(FUNC, ARGS, ELSE) \
122 __libc_maybe_call (FUNC, ARGS, ELSE)
123# define __libc_ptf_call_always(FUNC, ARGS) \
124 FUNC ARGS
125#endif
126
127
128/* Initialize the named lock variable, leaving it in a consistent, unlocked
129 state. */
130#if IS_IN (libc) || IS_IN (libpthread)
131# define __libc_lock_init(NAME) \
132 ((void) ((NAME) = LLL_LOCK_INITIALIZER))
133#else
134# define __libc_lock_init(NAME) \
135 __libc_maybe_call (__pthread_mutex_init, (&(NAME), NULL), 0)
136#endif
137#if defined SHARED && IS_IN (libc)
138/* ((NAME) = (__libc_rwlock_t) PTHREAD_RWLOCK_INITIALIZER) is inefficient. */
139# define __libc_rwlock_init(NAME) \
140 ((void) __builtin_memset (&(NAME), '\0', sizeof (NAME)))
141#else
142# define __libc_rwlock_init(NAME) \
143 __libc_maybe_call (__pthread_rwlock_init, (&(NAME), NULL), 0)
144#endif
145
146/* Finalize the named lock variable, which must be locked. It cannot be
147 used again until __libc_lock_init is called again on it. This must be
148 called on a lock variable before the containing storage is reused. */
149#if IS_IN (libc) || IS_IN (libpthread)
150# define __libc_lock_fini(NAME) ((void) 0)
151#else
152# define __libc_lock_fini(NAME) \
153 __libc_maybe_call (__pthread_mutex_destroy, (&(NAME)), 0)
154#endif
155#if defined SHARED && IS_IN (libc)
156# define __libc_rwlock_fini(NAME) ((void) 0)
157#else
158# define __libc_rwlock_fini(NAME) \
159 __libc_maybe_call (__pthread_rwlock_destroy, (&(NAME)), 0)
160#endif
161
162/* Lock the named lock variable. */
163#if IS_IN (libc) || IS_IN (libpthread)
164# ifndef __libc_lock_lock
165# define __libc_lock_lock(NAME) \
166 ({ lll_lock (NAME, LLL_PRIVATE); 0; })
167# endif
168#else
169# undef __libc_lock_lock
170# define __libc_lock_lock(NAME) \
171 __libc_maybe_call (__pthread_mutex_lock, (&(NAME)), 0)
172#endif
173#define __libc_rwlock_rdlock(NAME) \
174 __libc_ptf_call (__pthread_rwlock_rdlock, (&(NAME)), 0)
175#define __libc_rwlock_wrlock(NAME) \
176 __libc_ptf_call (__pthread_rwlock_wrlock, (&(NAME)), 0)
177
178/* Try to lock the named lock variable. */
179#if IS_IN (libc) || IS_IN (libpthread)
180# ifndef __libc_lock_trylock
181# define __libc_lock_trylock(NAME) \
182 lll_trylock (NAME)
183# endif
184#else
185# undef __libc_lock_trylock
186# define __libc_lock_trylock(NAME) \
187 __libc_maybe_call (__pthread_mutex_trylock, (&(NAME)), 0)
188#endif
189#define __libc_rwlock_tryrdlock(NAME) \
190 __libc_maybe_call (__pthread_rwlock_tryrdlock, (&(NAME)), 0)
191#define __libc_rwlock_trywrlock(NAME) \
192 __libc_maybe_call (__pthread_rwlock_trywrlock, (&(NAME)), 0)
193
194#define __rtld_lock_trylock_recursive(NAME) \
195 __libc_maybe_call (__pthread_mutex_trylock, (&(NAME).mutex), 0)
196
197/* Unlock the named lock variable. */
198#if IS_IN (libc) || IS_IN (libpthread)
199# define __libc_lock_unlock(NAME) \
200 lll_unlock (NAME, LLL_PRIVATE)
201#else
202# define __libc_lock_unlock(NAME) \
203 __libc_maybe_call (__pthread_mutex_unlock, (&(NAME)), 0)
204#endif
205#define __libc_rwlock_unlock(NAME) \
206 __libc_ptf_call (__pthread_rwlock_unlock, (&(NAME)), 0)
207
208#ifdef SHARED
209# define __rtld_lock_default_lock_recursive(lock) \
210 ++((pthread_mutex_t *)(lock))->__data.__count;
211
212# define __rtld_lock_default_unlock_recursive(lock) \
213 --((pthread_mutex_t *)(lock))->__data.__count;
214
215# define __rtld_lock_lock_recursive(NAME) \
216 GL(dl_rtld_lock_recursive) (&(NAME).mutex)
217
218# define __rtld_lock_unlock_recursive(NAME) \
219 GL(dl_rtld_unlock_recursive) (&(NAME).mutex)
220#else
221# define __rtld_lock_lock_recursive(NAME) \
222 __libc_maybe_call (__pthread_mutex_lock, (&(NAME).mutex), 0)
223
224# define __rtld_lock_unlock_recursive(NAME) \
225 __libc_maybe_call (__pthread_mutex_unlock, (&(NAME).mutex), 0)
226#endif
227
228/* Define once control variable. */
229#if PTHREAD_ONCE_INIT == 0
230/* Special case for static variables where we can avoid the initialization
231 if it is zero. */
232# define __libc_once_define(CLASS, NAME) \
233 CLASS pthread_once_t NAME
234#else
235# define __libc_once_define(CLASS, NAME) \
236 CLASS pthread_once_t NAME = PTHREAD_ONCE_INIT
237#endif
238
239/* Call handler iff the first call. */
240#define __libc_once(ONCE_CONTROL, INIT_FUNCTION) \
241 do { \
242 if (PTFAVAIL (__pthread_once)) \
243 __libc_ptf_call_always (__pthread_once, (&(ONCE_CONTROL), \
244 INIT_FUNCTION)); \
245 else if ((ONCE_CONTROL) == PTHREAD_ONCE_INIT) { \
246 INIT_FUNCTION (); \
247 (ONCE_CONTROL) |= 2; \
248 } \
249 } while (0)
250
251/* Get once control variable. */
252#define __libc_once_get(ONCE_CONTROL) ((ONCE_CONTROL) != PTHREAD_ONCE_INIT)
253
254/* Note that for I/O cleanup handling we are using the old-style
255 cancel handling. It does not have to be integrated with C++ snce
256 no C++ code is called in the middle. The old-style handling is
257 faster and the support is not going away. */
258extern void _pthread_cleanup_push (struct _pthread_cleanup_buffer *buffer,
259 void (*routine) (void *), void *arg);
260extern void _pthread_cleanup_pop (struct _pthread_cleanup_buffer *buffer,
261 int execute);
262extern void _pthread_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer,
263 void (*routine) (void *), void *arg);
264extern void _pthread_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer,
265 int execute);
266
267/* Sometimes we have to exit the block in the middle. */
268#define __libc_cleanup_end(DOIT) \
269 if (_avail) { \
270 __libc_ptf_call_always (_pthread_cleanup_pop_restore, (&_buffer, DOIT));\
271 } else if (DOIT) \
272 _buffer.__routine (_buffer.__arg)
273
274
275/* Normal cleanup handling, based on C cleanup attribute. */
276__extern_inline void
277__libc_cleanup_routine (struct __pthread_cleanup_frame *f)
278{
279 if (f->__do_it)
280 f->__cancel_routine (f->__cancel_arg);
281}
282
283#define __libc_cleanup_push(fct, arg) \
284 do { \
285 struct __pthread_cleanup_frame __clframe \
286 __attribute__ ((__cleanup__ (__libc_cleanup_routine))) \
287 = { .__cancel_routine = (fct), .__cancel_arg = (arg), \
288 .__do_it = 1 };
289
290#define __libc_cleanup_pop(execute) \
291 __clframe.__do_it = (execute); \
292 } while (0)
293
294
295/* Create thread-specific key. */
296#define __libc_key_create(KEY, DESTRUCTOR) \
297 __libc_ptf_call (__pthread_key_create, (KEY, DESTRUCTOR), 1)
298
299/* Get thread-specific data. */
300#define __libc_getspecific(KEY) \
301 __libc_ptf_call (__pthread_getspecific, (KEY), NULL)
302
303/* Set thread-specific data. */
304#define __libc_setspecific(KEY, VALUE) \
305 __libc_ptf_call (__pthread_setspecific, (KEY, VALUE), 0)
306
307
308/* Register handlers to execute before and after `fork'. Note that the
309 last parameter is NULL. The handlers registered by the libc are
310 never removed so this is OK. */
311extern int __register_atfork (void (*__prepare) (void),
312 void (*__parent) (void),
313 void (*__child) (void),
314 void *__dso_handle);
315
316/* Functions that are used by this file and are internal to the GNU C
317 library. */
318
319extern int __pthread_mutex_init (pthread_mutex_t *__mutex,
320 const pthread_mutexattr_t *__mutex_attr);
321
322extern int __pthread_mutex_destroy (pthread_mutex_t *__mutex);
323
324extern int __pthread_mutex_trylock (pthread_mutex_t *__mutex);
325
326extern int __pthread_mutex_lock (pthread_mutex_t *__mutex);
327
328extern int __pthread_mutex_unlock (pthread_mutex_t *__mutex);
329
330extern int __pthread_mutexattr_init (pthread_mutexattr_t *__attr);
331
332extern int __pthread_mutexattr_destroy (pthread_mutexattr_t *__attr);
333
334extern int __pthread_mutexattr_settype (pthread_mutexattr_t *__attr,
335 int __kind);
336
337extern int __pthread_rwlock_init (pthread_rwlock_t *__rwlock,
338 const pthread_rwlockattr_t *__attr);
339
340extern int __pthread_rwlock_destroy (pthread_rwlock_t *__rwlock);
341
342extern int __pthread_rwlock_rdlock (pthread_rwlock_t *__rwlock);
343
344extern int __pthread_rwlock_tryrdlock (pthread_rwlock_t *__rwlock);
345
346extern int __pthread_rwlock_wrlock (pthread_rwlock_t *__rwlock);
347
348extern int __pthread_rwlock_trywrlock (pthread_rwlock_t *__rwlock);
349
350extern int __pthread_rwlock_unlock (pthread_rwlock_t *__rwlock);
351
352extern int __pthread_key_create (pthread_key_t *__key,
353 void (*__destr_function) (void *));
354
355extern int __pthread_setspecific (pthread_key_t __key,
356 const void *__pointer);
357
358extern void *__pthread_getspecific (pthread_key_t __key);
359
360extern int __pthread_once (pthread_once_t *__once_control,
361 void (*__init_routine) (void));
362
363extern int __pthread_atfork (void (*__prepare) (void),
364 void (*__parent) (void),
365 void (*__child) (void));
366
367extern int __pthread_setcancelstate (int state, int *oldstate);
368
369
370/* Make the pthread functions weak so that we can elide them from
371 single-threaded processes. */
372#ifndef __NO_WEAK_PTHREAD_ALIASES
373# ifdef weak_extern
374weak_extern (__pthread_mutex_init)
375weak_extern (__pthread_mutex_destroy)
376weak_extern (__pthread_mutex_lock)
377weak_extern (__pthread_mutex_trylock)
378weak_extern (__pthread_mutex_unlock)
379weak_extern (__pthread_mutexattr_init)
380weak_extern (__pthread_mutexattr_destroy)
381weak_extern (__pthread_mutexattr_settype)
382weak_extern (__pthread_rwlock_init)
383weak_extern (__pthread_rwlock_destroy)
384weak_extern (__pthread_rwlock_rdlock)
385weak_extern (__pthread_rwlock_tryrdlock)
386weak_extern (__pthread_rwlock_wrlock)
387weak_extern (__pthread_rwlock_trywrlock)
388weak_extern (__pthread_rwlock_unlock)
389weak_extern (__pthread_key_create)
390weak_extern (__pthread_setspecific)
391weak_extern (__pthread_getspecific)
392weak_extern (__pthread_once)
393weak_extern (__pthread_initialize)
394weak_extern (__pthread_atfork)
395weak_extern (__pthread_setcancelstate)
396weak_extern (_pthread_cleanup_push_defer)
397weak_extern (_pthread_cleanup_pop_restore)
398# else
399# pragma weak __pthread_mutex_init
400# pragma weak __pthread_mutex_destroy
401# pragma weak __pthread_mutex_lock
402# pragma weak __pthread_mutex_trylock
403# pragma weak __pthread_mutex_unlock
404# pragma weak __pthread_mutexattr_init
405# pragma weak __pthread_mutexattr_destroy
406# pragma weak __pthread_mutexattr_settype
407# pragma weak __pthread_rwlock_destroy
408# pragma weak __pthread_rwlock_rdlock
409# pragma weak __pthread_rwlock_tryrdlock
410# pragma weak __pthread_rwlock_wrlock
411# pragma weak __pthread_rwlock_trywrlock
412# pragma weak __pthread_rwlock_unlock
413# pragma weak __pthread_key_create
414# pragma weak __pthread_setspecific
415# pragma weak __pthread_getspecific
416# pragma weak __pthread_once
417# pragma weak __pthread_initialize
418# pragma weak __pthread_atfork
419# pragma weak __pthread_setcancelstate
420# pragma weak _pthread_cleanup_push_defer
421# pragma weak _pthread_cleanup_pop_restore
422# endif
423#endif
424
425#endif /* libc-lockP.h */
426