2 #include "pthread_impl.h"
3 #include "stdio_impl.h"
9 void *__mmap(void *, size_t, int, int, int, off_t);
10 int __munmap(void *, size_t);
11 int __mprotect(void *, size_t, int);
16 weak_alias(dummy_0, __acquire_ptc);
17 weak_alias(dummy_0, __release_ptc);
18 weak_alias(dummy_0, __pthread_tsd_run_dtors);
19 weak_alias(dummy_0, __do_orphaned_stdio_locks);
20 weak_alias(dummy_0, __dl_thread_cleanup);
22 static void *dummy_1(void *p)
26 weak_alias(dummy_1, __start_sched);
28 _Noreturn void __pthread_exit(void *result)
30 pthread_t self = __pthread_self();
33 self->canceldisable = 1;
34 self->cancelasync = 0;
35 self->result = result;
37 while (self->cancelbuf) {
38 void (*f)(void *) = self->cancelbuf->__f;
39 void *x = self->cancelbuf->__x;
40 self->cancelbuf = self->cancelbuf->__next;
44 __pthread_tsd_run_dtors();
46 /* Access to target the exiting thread with syscalls that use
47 * its kernel tid is controlled by killlock. For detached threads,
48 * any use past this point would have undefined behavior, but for
49 * joinable threads it's a valid usage that must be handled. */
52 /* Block all signals before decrementing the live thread count.
53 * This is important to ensure that dynamically allocated TLS
54 * is not under-allocated/over-committed, and possibly for other
56 __block_all_sigs(&set);
58 /* It's impossible to determine whether this is "the last thread"
59 * until performing the atomic decrement, since multiple threads
60 * could exit at the same time. For the last thread, revert the
61 * decrement, restore the tid, and unblock signals to give the
62 * atexit handlers and stdio cleanup code a consistent state. */
63 if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
64 libc.threads_minus_1 = 0;
65 UNLOCK(self->killlock);
70 /* Process robust list in userspace to handle non-pshared mutexes
71 * and the detached thread case where the robust list head will
72 * be invalid when the kernel would process it. */
74 volatile void *volatile *rp;
75 while ((rp=self->robust_list.head) && rp != &self->robust_list.head) {
76 pthread_mutex_t *m = (void *)((char *)rp
77 - offsetof(pthread_mutex_t, _m_next));
78 int waiters = m->_m_waiters;
79 int priv = (m->_m_type & 128) ^ 128;
80 self->robust_list.pending = rp;
81 self->robust_list.head = *rp;
82 int cont = a_swap(&m->_m_lock, 0x40000000);
83 self->robust_list.pending = 0;
84 if (cont < 0 || waiters)
85 __wake(&m->_m_lock, 1, priv);
89 __do_orphaned_stdio_locks();
90 __dl_thread_cleanup();
92 /* This atomic potentially competes with a concurrent pthread_detach
93 * call; the loser is responsible for freeing thread resources. */
94 int state = a_cas(&self->detach_state, DT_JOINABLE, DT_EXITING);
96 if (state>=DT_DETACHED && self->map_base) {
97 /* Detached threads must avoid the kernel clear_child_tid
98 * feature, since the virtual address will have been
99 * unmapped and possibly already reused by a new mapping
100 * at the time the kernel would perform the write. In
101 * the case of threads that started out detached, the
102 * initial clone flags are correct, but if the thread was
103 * detached later, we need to clear it here. */
104 if (state == DT_DYNAMIC) __syscall(SYS_set_tid_address, 0);
106 /* Robust list will no longer be valid, and was already
107 * processed above, so unregister it with the kernel. */
108 if (self->robust_list.off)
109 __syscall(SYS_set_robust_list, 0, 3*sizeof(long));
111 /* Since __unmapself bypasses the normal munmap code path,
112 * explicitly wait for vmlock holders first. */
115 /* The following call unmaps the thread's stack mapping
116 * and then exits without touching the stack. */
117 __unmapself(self->map_base, self->map_size);
120 /* After the kernel thread exits, its tid may be reused. Clear it
121 * to prevent inadvertent use and inform functions that would use
122 * it that it's no longer available. */
124 UNLOCK(self->killlock);
126 for (;;) __syscall(SYS_exit, 0);
129 void __do_cleanup_push(struct __ptcb *cb)
131 struct pthread *self = __pthread_self();
132 cb->__next = self->cancelbuf;
133 self->cancelbuf = cb;
136 void __do_cleanup_pop(struct __ptcb *cb)
138 __pthread_self()->cancelbuf = cb->__next;
141 static int start(void *p)
144 if (self->unblock_cancel)
145 __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
146 SIGPT_SET, 0, _NSIG/8);
147 __pthread_exit(self->start(self->start_arg));
151 static int start_c11(void *p)
154 int (*start)(void*) = (int(*)(void*)) self->start;
155 __pthread_exit((void *)(uintptr_t)start(self->start_arg));
159 #define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE)
161 /* pthread_key_create.c overrides this */
162 static volatile size_t dummy = 0;
163 weak_alias(dummy, __pthread_tsd_size);
164 static void *dummy_tsd[1] = { 0 };
165 weak_alias(dummy_tsd, __pthread_tsd_main);
167 volatile int __block_new_threads = 0;
168 extern size_t __default_stacksize;
169 extern size_t __default_guardsize;
171 static FILE *volatile dummy_file = 0;
172 weak_alias(dummy_file, __stdin_used);
173 weak_alias(dummy_file, __stdout_used);
174 weak_alias(dummy_file, __stderr_used);
176 static void init_file_lock(FILE *f)
178 if (f && f->lock<0) f->lock = 0;
181 int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
183 int ret, c11 = (attrp == __ATTRP_C11_THREAD);
185 struct pthread *self, *new;
186 unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
187 unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
188 | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
189 | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
191 pthread_attr_t attr = { 0 };
192 struct start_sched_args ssa;
194 if (!libc.can_do_threads) return ENOSYS;
195 self = __pthread_self();
196 if (!libc.threaded) {
197 for (FILE *f=*__ofl_lock(); f; f=f->next)
200 init_file_lock(__stdin_used);
201 init_file_lock(__stdout_used);
202 init_file_lock(__stderr_used);
203 __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8);
204 self->tsd = (void **)__pthread_tsd_main;
207 if (attrp && !c11) attr = *attrp;
211 attr._a_stacksize = __default_stacksize;
212 attr._a_guardsize = __default_guardsize;
215 if (__block_new_threads) __wait(&__block_new_threads, 0, 1, 1);
217 if (attr._a_stackaddr) {
218 size_t need = libc.tls_size + __pthread_tsd_size;
219 size = attr._a_stacksize;
220 stack = (void *)(attr._a_stackaddr & -16);
221 stack_limit = (void *)(attr._a_stackaddr - size);
222 /* Use application-provided stack for TLS only when
223 * it does not take more than ~12% or 2k of the
224 * application's stack space. */
225 if (need < size/8 && need < 2048) {
226 tsd = stack - __pthread_tsd_size;
227 stack = tsd - libc.tls_size;
228 memset(stack, 0, need);
234 guard = ROUND(attr._a_guardsize);
235 size = guard + ROUND(attr._a_stacksize
236 + libc.tls_size + __pthread_tsd_size);
241 map = __mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
242 if (map == MAP_FAILED) goto fail;
243 if (__mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)
244 && errno != ENOSYS) {
249 map = __mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
250 if (map == MAP_FAILED) goto fail;
252 tsd = map + size - __pthread_tsd_size;
254 stack = tsd - libc.tls_size;
255 stack_limit = map + guard;
259 new = __copy_tls(tsd - libc.tls_size);
261 new->map_size = size;
263 new->stack_size = stack - stack_limit;
264 new->guard_size = guard;
266 new->start_arg = arg;
268 new->tsd = (void *)tsd;
269 new->locale = &libc.global_locale;
270 if (attr._a_detach) {
271 new->detach_state = DT_DETACHED;
272 flags -= CLONE_CHILD_CLEARTID;
274 new->detach_state = DT_JOINABLE;
279 ssa.start_fn = new->start;
280 ssa.start_arg = new->start_arg;
282 new->start = __start_sched;
283 new->start_arg = &ssa;
284 __block_app_sigs(&ssa.mask);
286 new->robust_list.head = &new->robust_list.head;
287 new->unblock_cancel = self->cancel;
288 new->CANARY = self->CANARY;
290 a_inc(&libc.threads_minus_1);
291 ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->detach_state);
296 __restore_sigs(&ssa.mask);
300 a_dec(&libc.threads_minus_1);
301 if (map) __munmap(map, size);
306 __futexwait(&ssa.futex, -1, 1);
318 weak_alias(__pthread_exit, pthread_exit);
319 weak_alias(__pthread_create, pthread_create);