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();
42 /* Access to target the exiting thread with syscalls that use
43 * its kernel tid is controlled by killlock. For detached threads,
44 * any use past this point would have undefined behavior, but for
45 * joinable threads it's a valid usage that must be handled. */
48 /* Block all signals before decrementing the live thread count.
49 * This is important to ensure that dynamically allocated TLS
50 * is not under-allocated/over-committed, and possibly for other
52 __block_all_sigs(&set);
54 /* It's impossible to determine whether this is "the last thread"
55 * until performing the atomic decrement, since multiple threads
56 * could exit at the same time. For the last thread, revert the
57 * decrement, restore the tid, and unblock signals to give the
58 * atexit handlers and stdio cleanup code a consistent state. */
59 if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
60 libc.threads_minus_1 = 0;
61 UNLOCK(self->killlock);
66 /* Process robust list in userspace to handle non-pshared mutexes
67 * and the detached thread case where the robust list head will
68 * be invalid when the kernel would process it. */
70 volatile void *volatile *rp;
71 while ((rp=self->robust_list.head) && rp != &self->robust_list.head) {
72 pthread_mutex_t *m = (void *)((char *)rp
73 - offsetof(pthread_mutex_t, _m_next));
74 int waiters = m->_m_waiters;
75 int priv = (m->_m_type & 128) ^ 128;
76 self->robust_list.pending = rp;
77 self->robust_list.head = *rp;
78 int cont = a_swap(&m->_m_lock, 0x40000000);
79 self->robust_list.pending = 0;
80 if (cont < 0 || waiters)
81 __wake(&m->_m_lock, 1, priv);
85 __do_orphaned_stdio_locks();
86 __dl_thread_cleanup();
88 if (self->detached && self->map_base) {
89 /* Detached threads must avoid the kernel clear_child_tid
90 * feature, since the virtual address will have been
91 * unmapped and possibly already reused by a new mapping
92 * at the time the kernel would perform the write. In
93 * the case of threads that started out detached, the
94 * initial clone flags are correct, but if the thread was
95 * detached later (== 2), we need to clear it here. */
96 if (self->detached == 2) __syscall(SYS_set_tid_address, 0);
98 /* Robust list will no longer be valid, and was already
99 * processed above, so unregister it with the kernel. */
100 if (self->robust_list.off)
101 __syscall(SYS_set_robust_list, 0, 3*sizeof(long));
103 /* Since __unmapself bypasses the normal munmap code path,
104 * explicitly wait for vmlock holders first. */
107 /* The following call unmaps the thread's stack mapping
108 * and then exits without touching the stack. */
109 __unmapself(self->map_base, self->map_size);
112 /* After the kernel thread exits, its tid may be reused. Clear it
113 * to prevent inadvertent use and inform functions that would use
114 * it that it's no longer available. */
116 UNLOCK(self->killlock);
118 for (;;) __syscall(SYS_exit, 0);
121 void __do_cleanup_push(struct __ptcb *cb)
123 struct pthread *self = __pthread_self();
124 cb->__next = self->cancelbuf;
125 self->cancelbuf = cb;
128 void __do_cleanup_pop(struct __ptcb *cb)
130 __pthread_self()->cancelbuf = cb->__next;
133 static int start(void *p)
136 /* States for startlock:
137 * 0 = no need for start sync
138 * 1 = waiting for parent to do work
139 * 2 = failure in parent, child must abort
140 * 3 = success in parent, child must restore sigmask */
141 if (self->startlock[0]) {
142 __wait(self->startlock, 0, 1, 1);
143 if (self->startlock[0] == 2) {
147 __restore_sigs(self->sigmask);
149 if (self->unblock_cancel)
150 __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
151 SIGPT_SET, 0, _NSIG/8);
152 __pthread_exit(self->start(self->start_arg));
156 static int start_c11(void *p)
159 int (*start)(void*) = (int(*)(void*)) self->start;
160 __pthread_exit((void *)(uintptr_t)start(self->start_arg));
164 #define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE)
166 /* pthread_key_create.c overrides this */
167 static volatile size_t dummy = 0;
168 weak_alias(dummy, __pthread_tsd_size);
169 static void *dummy_tsd[1] = { 0 };
170 weak_alias(dummy_tsd, __pthread_tsd_main);
172 volatile int __block_new_threads = 0;
173 size_t __default_stacksize = DEFAULT_STACK_SIZE;
174 size_t __default_guardsize = DEFAULT_GUARD_SIZE;
176 static FILE *volatile dummy_file = 0;
177 weak_alias(dummy_file, __stdin_used);
178 weak_alias(dummy_file, __stdout_used);
179 weak_alias(dummy_file, __stderr_used);
181 static void init_file_lock(FILE *f)
183 if (f && f->lock<0) f->lock = 0;
186 void *__copy_tls(unsigned char *);
188 int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
190 int ret, c11 = (attrp == __ATTRP_C11_THREAD);
192 struct pthread *self, *new;
193 unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
194 unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
195 | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
196 | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
198 pthread_attr_t attr = { 0 };
200 if (!libc.can_do_threads) return ENOSYS;
201 self = __pthread_self();
202 if (!libc.threaded) {
203 for (FILE *f=*__ofl_lock(); f; f=f->next)
206 init_file_lock(__stdin_used);
207 init_file_lock(__stdout_used);
208 init_file_lock(__stderr_used);
209 __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8);
210 self->tsd = (void **)__pthread_tsd_main;
213 if (attrp && !c11) attr = *attrp;
217 attr._a_stacksize = __default_stacksize;
218 attr._a_guardsize = __default_guardsize;
221 if (__block_new_threads) __wait(&__block_new_threads, 0, 1, 1);
223 if (attr._a_stackaddr) {
224 size_t need = libc.tls_size + __pthread_tsd_size;
225 size = attr._a_stacksize;
226 stack = (void *)(attr._a_stackaddr & -16);
227 stack_limit = (void *)(attr._a_stackaddr - size);
228 /* Use application-provided stack for TLS only when
229 * it does not take more than ~12% or 2k of the
230 * application's stack space. */
231 if (need < size/8 && need < 2048) {
232 tsd = stack - __pthread_tsd_size;
233 stack = tsd - libc.tls_size;
234 memset(stack, 0, need);
240 guard = ROUND(attr._a_guardsize);
241 size = guard + ROUND(attr._a_stacksize
242 + libc.tls_size + __pthread_tsd_size);
247 map = __mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
248 if (map == MAP_FAILED) goto fail;
249 if (__mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)
250 && errno != ENOSYS) {
255 map = __mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
256 if (map == MAP_FAILED) goto fail;
258 tsd = map + size - __pthread_tsd_size;
260 stack = tsd - libc.tls_size;
261 stack_limit = map + guard;
265 new = __copy_tls(tsd - libc.tls_size);
267 new->map_size = size;
269 new->stack_size = stack - stack_limit;
270 new->guard_size = guard;
272 new->start_arg = arg;
274 new->tsd = (void *)tsd;
275 new->locale = &libc.global_locale;
276 if (attr._a_detach) {
278 flags -= CLONE_CHILD_CLEARTID;
281 do_sched = new->startlock[0] = 1;
282 __block_app_sigs(new->sigmask);
284 new->robust_list.head = &new->robust_list.head;
285 new->unblock_cancel = self->cancel;
286 new->CANARY = self->CANARY;
287 new->join_futex = -1;
289 a_inc(&libc.threads_minus_1);
290 ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->join_futex);
295 __restore_sigs(new->sigmask);
299 a_dec(&libc.threads_minus_1);
300 if (map) __munmap(map, size);
305 ret = __syscall(SYS_sched_setscheduler, new->tid,
306 attr._a_policy, &attr._a_prio);
307 a_store(new->startlock, ret<0 ? 2 : 3);
308 __wake(new->startlock, 1, 1);
309 if (ret < 0) return -ret;
319 weak_alias(__pthread_exit, pthread_exit);
320 weak_alias(__pthread_create, pthread_create);