source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/thread/pthread_create.c@ 400

#define _GNU_SOURCE
#include "pthread_impl.h"
#include "stdio_impl.h"
#include "libc.h"
#include <sys/mman.h>
#include <string.h>
#include <stddef.h>

void *__mmap(void *, size_t, int, int, int, off_t);
int __munmap(void *, size_t);
int __mprotect(void *, size_t, int);

static void dummy_0()
{
}
weak_alias(dummy_0, __acquire_ptc);
weak_alias(dummy_0, __release_ptc);
weak_alias(dummy_0, __pthread_tsd_run_dtors);
weak_alias(dummy_0, __do_orphaned_stdio_locks);
weak_alias(dummy_0, __dl_thread_cleanup);

_Noreturn void __pthread_exit(void *result)
{
        pthread_t self = __pthread_self();
        sigset_t set;

        self->canceldisable = 1;
        self->cancelasync = 0;
        self->result = result;

        while (self->cancelbuf) {
                void (*f)(void *) = self->cancelbuf->__f;
                void *x = self->cancelbuf->__x;
                self->cancelbuf = self->cancelbuf->__next;
                f(x);
        }

        __pthread_tsd_run_dtors();

        __lock(self->exitlock);

        /* Mark this thread dead before decrementing count */
        __lock(self->killlock);
        self->dead = 1;

        /* Block all signals before decrementing the live thread count.
         * This is important to ensure that dynamically allocated TLS
         * is not under-allocated/over-committed, and possibly for other
         * reasons as well. */
        __block_all_sigs(&set);

        /* Wait to unlock the kill lock, which governs functions like
         * pthread_kill which target a thread id, until signals have
         * been blocked. This precludes observation of the thread id
         * as a live thread (with application code running in it) after
         * the thread was reported dead by ESRCH being returned. */
        __unlock(self->killlock);

        /* It's impossible to determine whether this is "the last thread"
         * until performing the atomic decrement, since multiple threads
         * could exit at the same time. For the last thread, revert the
         * decrement and unblock signals to give the atexit handlers and
         * stdio cleanup code a consistent state. */
        if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
                libc.threads_minus_1 = 0;
                __restore_sigs(&set);
                exit(0);
        }

        /* Process robust list in userspace to handle non-pshared mutexes
         * and the detached thread case where the robust list head will
         * be invalid when the kernel would process it. */
        __vm_lock();
        volatile void *volatile *rp;
        while ((rp=self->robust_list.head) && rp != &self->robust_list.head) {
                pthread_mutex_t *m = (void *)((char *)rp
                        - offsetof(pthread_mutex_t, _m_next));
                int waiters = m->_m_waiters;
                int priv = (m->_m_type & 128) ^ 128;
                self->robust_list.pending = rp;
                self->robust_list.head = *rp;
                int cont = a_swap(&m->_m_lock, 0x40000000);
                self->robust_list.pending = 0;
                if (cont < 0 || waiters)
                        __wake(&m->_m_lock, 1, priv);
        }
        __vm_unlock();

        __do_orphaned_stdio_locks();
        __dl_thread_cleanup();

        if (self->detached && self->map_base) {
                /* Detached threads must avoid the kernel clear_child_tid
                 * feature, since the virtual address will have been
                 * unmapped and possibly already reused by a new mapping
                 * at the time the kernel would perform the write. In
                 * the case of threads that started out detached, the
                 * initial clone flags are correct, but if the thread was
                 * detached later (== 2), we need to clear it here. */
                if (self->detached == 2) __syscall(SYS_set_tid_address, 0);

                /* Robust list will no longer be valid, and was already
                 * processed above, so unregister it with the kernel. */
                if (self->robust_list.off)
                        __syscall(SYS_set_robust_list, 0, 3*sizeof(long));

                /* Since __unmapself bypasses the normal munmap code path,
                 * explicitly wait for vmlock holders first. */
                __vm_wait();

                /* The following call unmaps the thread's stack mapping
                 * and then exits without touching the stack. */
                __unmapself(self->map_base, self->map_size);
        }

        for (;;) __syscall(SYS_exit, 0);
}

void __do_cleanup_push(struct __ptcb *cb)
{
        struct pthread *self = __pthread_self();
        cb->__next = self->cancelbuf;
        self->cancelbuf = cb;
}

void __do_cleanup_pop(struct __ptcb *cb)
{
        __pthread_self()->cancelbuf = cb->__next;
}

static int start(void *p)
{
        pthread_t self = p;
        /* States for startlock:
         * 0 = no need for start sync
         * 1 = waiting for parent to do work
         * 2 = failure in parent, child must abort
         * 3 = success in parent, child must restore sigmask */
        if (self->startlock[0]) {
                __wait(self->startlock, 0, 1, 1);
                if (self->startlock[0] == 2) {
                        self->detached = 2;
                        pthread_exit(0);
                }
                __restore_sigs(self->sigmask);
        }
        if (self->unblock_cancel)
                __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
                        SIGPT_SET, 0, _NSIG/8);
        __pthread_exit(self->start(self->start_arg));
        return 0;
}

static int start_c11(void *p)
{
        pthread_t self = p;
        int (*start)(void*) = (int(*)(void*)) self->start;
        __pthread_exit((void *)(uintptr_t)start(self->start_arg));
        return 0;
}

#define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE)

/* pthread_key_create.c overrides this */
static volatile size_t dummy = 0;
weak_alias(dummy, __pthread_tsd_size);
static void *dummy_tsd[1] = { 0 };
weak_alias(dummy_tsd, __pthread_tsd_main);

volatile int __block_new_threads = 0;
size_t __default_stacksize = DEFAULT_STACK_SIZE;
size_t __default_guardsize = DEFAULT_GUARD_SIZE;

static FILE *volatile dummy_file = 0;
weak_alias(dummy_file, __stdin_used);
weak_alias(dummy_file, __stdout_used);
weak_alias(dummy_file, __stderr_used);

static void init_file_lock(FILE *f)
{
        if (f && f->lock<0) f->lock = 0;
}

void *__copy_tls(unsigned char *);

int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg)
{
        int ret, c11 = (attrp == __ATTRP_C11_THREAD);
        size_t size, guard;
        struct pthread *self, *new;
        unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
        unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
                | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
                | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
        int do_sched = 0;
        pthread_attr_t attr = { 0 };

        if (!libc.can_do_threads) return ENOSYS;
        self = __pthread_self();
        if (!libc.threaded) {
                for (FILE *f=*__ofl_lock(); f; f=f->next)
                        init_file_lock(f);
                __ofl_unlock();
                init_file_lock(__stdin_used);
                init_file_lock(__stdout_used);
                init_file_lock(__stderr_used);
                __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8);
                self->tsd = (void **)__pthread_tsd_main;
                libc.threaded = 1;
        }
        if (attrp && !c11) attr = *attrp;

        __acquire_ptc();
        if (!attrp || c11) {
                attr._a_stacksize = __default_stacksize;
                attr._a_guardsize = __default_guardsize;
        }

        if (__block_new_threads) __wait(&__block_new_threads, 0, 1, 1);

        if (attr._a_stackaddr) {
                size_t need = libc.tls_size + __pthread_tsd_size;
                size = attr._a_stacksize;
                stack = (void *)(attr._a_stackaddr & -16);
                stack_limit = (void *)(attr._a_stackaddr - size);
                /* Use application-provided stack for TLS only when
                 * it does not take more than ~12% or 2k of the
                 * application's stack space. */
                if (need < size/8 && need < 2048) {
                        tsd = stack - __pthread_tsd_size;
                        stack = tsd - libc.tls_size;
                        memset(stack, 0, need);
                } else {
                        size = ROUND(need);
                        guard = 0;
                }
        } else {
                guard = ROUND(attr._a_guardsize);
                size = guard + ROUND(attr._a_stacksize
                        + libc.tls_size +  __pthread_tsd_size);
        }

        if (!tsd) {
                if (guard) {
                        map = __mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
                        if (map == MAP_FAILED) goto fail;
                        if (__mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)
                            && errno != ENOSYS) {
                                __munmap(map, size);
                                goto fail;
                        }
                } else {
                        map = __mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
                        if (map == MAP_FAILED) goto fail;
                }
                tsd = map + size - __pthread_tsd_size;
                if (!stack) {
                        stack = tsd - libc.tls_size;
                        stack_limit = map + guard;
                }
        }

        new = __copy_tls(tsd - libc.tls_size);
        new->map_base = map;
        new->map_size = size;
        new->stack = stack;
        new->stack_size = stack - stack_limit;
        new->start = entry;
        new->start_arg = arg;
        new->self = new;
        new->tsd = (void *)tsd;
        new->locale = &libc.global_locale;
        if (attr._a_detach) {
                new->detached = 1;
                flags -= CLONE_CHILD_CLEARTID;
        }
        if (attr._a_sched) {
                do_sched = new->startlock[0] = 1;
                __block_app_sigs(new->sigmask);
        }
        new->robust_list.head = &new->robust_list.head;
        new->unblock_cancel = self->cancel;
        new->CANARY = self->CANARY;

        a_inc(&libc.threads_minus_1);
        ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->tid);

        __release_ptc();

        if (do_sched) {
                __restore_sigs(new->sigmask);
        }

        if (ret < 0) {
                a_dec(&libc.threads_minus_1);
                if (map) __munmap(map, size);
                return EAGAIN;
        }

        if (do_sched) {
                ret = __syscall(SYS_sched_setscheduler, new->tid,
                        attr._a_policy, &attr._a_prio);
                a_store(new->startlock, ret<0 ? 2 : 3);
                __wake(new->startlock, 1, 1);
                if (ret < 0) return -ret;
        }

        *res = new;
        return 0;
fail:
        __release_ptc();
        return EAGAIN;
}

weak_alias(__pthread_exit, pthread_exit);
weak_alias(__pthread_create, pthread_create);