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 _Noreturn void __pthread_exit(void *result)
24 pthread_t self = __pthread_self();
27 self->canceldisable = 1;
28 self->cancelasync = 0;
29 self->result = result;
31 while (self->cancelbuf) {
32 void (*f)(void *) = self->cancelbuf->__f;
33 void *x = self->cancelbuf->__x;
34 self->cancelbuf = self->cancelbuf->__next;
38 __pthread_tsd_run_dtors();
40 /* Access to target the exiting thread with syscalls that use
41 * its kernel tid is controlled by killlock. For detached threads,
42 * any use past this point would have undefined behavior, but for
43 * joinable threads it's a valid usage that must be handled. */
46 /* Block all signals before decrementing the live thread count.
47 * This is important to ensure that dynamically allocated TLS
48 * is not under-allocated/over-committed, and possibly for other
50 __block_all_sigs(&set);
52 /* It's impossible to determine whether this is "the last thread"
53 * until performing the atomic decrement, since multiple threads
54 * could exit at the same time. For the last thread, revert the
55 * decrement, restore the tid, and unblock signals to give the
56 * atexit handlers and stdio cleanup code a consistent state. */
57 if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
58 libc.threads_minus_1 = 0;
59 UNLOCK(self->killlock);
64 /* Process robust list in userspace to handle non-pshared mutexes
65 * and the detached thread case where the robust list head will
66 * be invalid when the kernel would process it. */
68 volatile void *volatile *rp;
69 while ((rp=self->robust_list.head) && rp != &self->robust_list.head) {
70 pthread_mutex_t *m = (void *)((char *)rp
71 - offsetof(pthread_mutex_t, _m_next));
72 int waiters = m->_m_waiters;
73 int priv = (m->_m_type & 128) ^ 128;
74 self->robust_list.pending = rp;
75 self->robust_list.head = *rp;
76 int cont = a_swap(&m->_m_lock, 0x40000000);
77 self->robust_list.pending = 0;
78 if (cont < 0 || waiters)
79 __wake(&m->_m_lock, 1, priv);
83 __do_orphaned_stdio_locks();
84 __dl_thread_cleanup();
86 /* This atomic potentially competes with a concurrent pthread_detach
87 * call; the loser is responsible for freeing thread resources. */
88 int state = a_cas(&self->detach_state, DT_JOINABLE, DT_EXITING);
90 if (state>=DT_DETACHED && self->map_base) {
91 /* Detached threads must avoid the kernel clear_child_tid
92 * feature, since the virtual address will have been
93 * unmapped and possibly already reused by a new mapping
94 * at the time the kernel would perform the write. In
95 * the case of threads that started out detached, the
96 * initial clone flags are correct, but if the thread was
97 * detached later, we need to clear it here. */
98 if (state == DT_DYNAMIC) __syscall(SYS_set_tid_address, 0);
100 /* Robust list will no longer be valid, and was already
101 * processed above, so unregister it with the kernel. */
102 if (self->robust_list.off)
103 __syscall(SYS_set_robust_list, 0, 3*sizeof(long));
105 /* Since __unmapself bypasses the normal munmap code path,
106 * explicitly wait for vmlock holders first. */
109 /* The following call unmaps the thread's stack mapping
110 * and then exits without touching the stack. */
111 __unmapself(self->map_base, self->map_size);
114 /* After the kernel thread exits, its tid may be reused. Clear it
115 * to prevent inadvertent use and inform functions that would use
116 * it that it's no longer available. */
118 UNLOCK(self->killlock);
120 for (;;) __syscall(SYS_exit, 0);
123 void __do_cleanup_push(struct __ptcb *cb)
125 struct pthread *self = __pthread_self();
126 cb->__next = self->cancelbuf;
127 self->cancelbuf = cb;
130 void __do_cleanup_pop(struct __ptcb *cb)
132 __pthread_self()->cancelbuf = cb->__next;
135 static int start(void *p)
138 /* States for startlock:
139 * 0 = no need for start sync
140 * 1 = waiting for parent to do work
141 * 2 = failure in parent, child must abort
142 * 3 = success in parent, child must restore sigmask */
143 if (self->startlock[0]) {
144 __wait(self->startlock, 0, 1, 1);
145 if (self->startlock[0] == 2) {
146 self->detach_state = DT_DYNAMIC;
149 __restore_sigs(self->sigmask);
151 if (self->unblock_cancel)
152 __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
153 SIGPT_SET, 0, _NSIG/8);
154 __pthread_exit(self->start(self->start_arg));
158 static int start_c11(void *p)
161 int (*start)(void*) = (int(*)(void*)) self->start;
162 __pthread_exit((void *)(uintptr_t)start(self->start_arg));
166 #define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE)
168 /* pthread_key_create.c overrides this */
169 static volatile size_t dummy = 0;
170 weak_alias(dummy, __pthread_tsd_size);
171 static void *dummy_tsd[1] = { 0 };
172 weak_alias(dummy_tsd, __pthread_tsd_main);
174 volatile int __block_new_threads = 0;
175 size_t __default_stacksize = DEFAULT_STACK_SIZE;
176 size_t __default_guardsize = DEFAULT_GUARD_SIZE;
178 static FILE *volatile dummy_file = 0;
179 weak_alias(dummy_file, __stdin_used);
180 weak_alias(dummy_file, __stdout_used);
181 weak_alias(dummy_file, __stderr_used);
183 static void init_file_lock(FILE *f)
185 if (f && f->lock<0) f->lock = 0;
188 void *__copy_tls(unsigned char *);
190 int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
192 int ret, c11 = (attrp == __ATTRP_C11_THREAD);
194 struct pthread *self, *new;
195 unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
196 unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
197 | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
198 | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
200 pthread_attr_t attr = { 0 };
202 if (!libc.can_do_threads) return ENOSYS;
203 self = __pthread_self();
204 if (!libc.threaded) {
205 for (FILE *f=*__ofl_lock(); f; f=f->next)
208 init_file_lock(__stdin_used);
209 init_file_lock(__stdout_used);
210 init_file_lock(__stderr_used);
211 __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8);
212 self->tsd = (void **)__pthread_tsd_main;
215 if (attrp && !c11) attr = *attrp;
219 attr._a_stacksize = __default_stacksize;
220 attr._a_guardsize = __default_guardsize;
223 if (__block_new_threads) __wait(&__block_new_threads, 0, 1, 1);
225 if (attr._a_stackaddr) {
226 size_t need = libc.tls_size + __pthread_tsd_size;
227 size = attr._a_stacksize;
228 stack = (void *)(attr._a_stackaddr & -16);
229 stack_limit = (void *)(attr._a_stackaddr - size);
230 /* Use application-provided stack for TLS only when
231 * it does not take more than ~12% or 2k of the
232 * application's stack space. */
233 if (need < size/8 && need < 2048) {
234 tsd = stack - __pthread_tsd_size;
235 stack = tsd - libc.tls_size;
236 memset(stack, 0, need);
242 guard = ROUND(attr._a_guardsize);
243 size = guard + ROUND(attr._a_stacksize
244 + libc.tls_size + __pthread_tsd_size);
249 map = __mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
250 if (map == MAP_FAILED) goto fail;
251 if (__mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)
252 && errno != ENOSYS) {
257 map = __mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
258 if (map == MAP_FAILED) goto fail;
260 tsd = map + size - __pthread_tsd_size;
262 stack = tsd - libc.tls_size;
263 stack_limit = map + guard;
267 new = __copy_tls(tsd - libc.tls_size);
269 new->map_size = size;
271 new->stack_size = stack - stack_limit;
272 new->guard_size = guard;
274 new->start_arg = arg;
276 new->tsd = (void *)tsd;
277 new->locale = &libc.global_locale;
278 if (attr._a_detach) {
279 new->detach_state = DT_DETACHED;
280 flags -= CLONE_CHILD_CLEARTID;
282 new->detach_state = DT_JOINABLE;
285 do_sched = new->startlock[0] = 1;
286 __block_app_sigs(new->sigmask);
288 new->robust_list.head = &new->robust_list.head;
289 new->unblock_cancel = self->cancel;
290 new->CANARY = self->CANARY;
292 a_inc(&libc.threads_minus_1);
293 ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->detach_state);
298 __restore_sigs(new->sigmask);
302 a_dec(&libc.threads_minus_1);
303 if (map) __munmap(map, size);
308 ret = __syscall(SYS_sched_setscheduler, new->tid,
309 attr._a_policy, &attr._a_prio);
310 a_store(new->startlock, ret<0 ? 2 : 3);
311 __wake(new->startlock, 1, 1);
312 if (ret < 0) return -ret;
322 weak_alias(__pthread_exit, pthread_exit);
323 weak_alias(__pthread_create, pthread_create);