Add a "fork" of musl as //fusl.

fusl/src/thread/pthread_create.c

+#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, self->tid|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;
+        if (self->startlock[0]) {
+                __wait(self->startlock, 0, 1, 1);
+                if (self->startlock[0]) {
+                        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;
+
+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 (__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 + DEFAULT_STACK_SIZE;
+                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(DEFAULT_GUARD_SIZE + attr._a_guardsize);
+                size = guard + ROUND(DEFAULT_STACK_SIZE + 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 : 0);
+                __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);