X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fthread%2Fpthread_create.c;h=087f6206d5d64165bc54ae741e77099994ae96e0;hb=d64148a8743ad9ed0594091d2ff141b1e9334d4b;hp=7a2f172cc16857489d028ee00ca523b2a147e8b5;hpb=df15168cf8baf34fb9c94e19eaa1a5c79c853970;p=musl diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c index 7a2f172c..087f6206 100644 --- a/src/thread/pthread_create.c +++ b/src/thread/pthread_create.c @@ -2,7 +2,10 @@ #include "pthread_impl.h" #include "stdio_impl.h" #include "libc.h" +#include "lock.h" #include +#include +#include static void dummy_0() { @@ -10,12 +13,51 @@ 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); +weak_alias(dummy_0, __membarrier_init); -_Noreturn void pthread_exit(void *result) +static int tl_lock_count; +static int tl_lock_waiters; + +void __tl_lock(void) +{ + int tid = __pthread_self()->tid; + int val = __thread_list_lock; + if (val == tid) { + tl_lock_count++; + return; + } + while ((val = a_cas(&__thread_list_lock, 0, tid))) + __wait(&__thread_list_lock, &tl_lock_waiters, val, 0); +} + +void __tl_unlock(void) +{ + if (tl_lock_count) { + tl_lock_count--; + return; + } + a_store(&__thread_list_lock, 0); + if (tl_lock_waiters) __wake(&__thread_list_lock, 1, 0); +} + +void __tl_sync(pthread_t td) +{ + a_barrier(); + int val = __thread_list_lock; + if (!val) return; + __wait(&__thread_list_lock, &tl_lock_waiters, val, 0); + if (tl_lock_waiters) __wake(&__thread_list_lock, 1, 0); +} + +_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) { @@ -27,57 +69,111 @@ _Noreturn void pthread_exit(void *result) __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; + __block_app_sigs(&set); + + /* This atomic potentially competes with a concurrent pthread_detach + * call; the loser is responsible for freeing thread resources. */ + int state = a_cas(&self->detach_state, DT_JOINABLE, DT_EXITING); + + if (state==DT_DETACHED && self->map_base) { + /* Since __unmapself bypasses the normal munmap code path, + * explicitly wait for vmlock holders first. This must be + * done before any locks are taken, to avoid lock ordering + * issues that could lead to deadlock. */ + __vm_wait(); + } + + /* Access to target the exiting thread with syscalls that use + * its kernel tid is controlled by killlock. For detached threads, + * any use past this point would have undefined behavior, but for + * joinable threads it's a valid usage that must be handled. + * Signals must be blocked since pthread_kill must be AS-safe. */ + LOCK(self->killlock); + + /* The thread list lock must be AS-safe, and thus depends on + * application signals being blocked above. */ + __tl_lock(); + + /* If this is the only thread in the list, don't proceed with + * termination of the thread, but restore the previous lock and + * signal state to prepare for exit to call atexit handlers. */ + if (self->next == self) { + __tl_unlock(); + UNLOCK(self->killlock); + self->detach_state = state; __restore_sigs(&set); exit(0); } - 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); + /* At this point we are committed to thread termination. */ + + /* After the kernel thread exits, its tid may be reused. Clear it + * to prevent inadvertent use and inform functions that would use + * it that it's no longer available. At this point the killlock + * may be released, since functions that use it will consistently + * see the thread as having exited. Release it now so that no + * remaining locks (except thread list) are held if we end up + * resetting need_locks below. */ + self->tid = 0; + UNLOCK(self->killlock); + + /* 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(); + + /* Last, unlink thread from the list. This change will not be visible + * until the lock is released, which only happens after SYS_exit + * has been called, via the exit futex address pointing at the lock. + * This needs to happen after any possible calls to LOCK() that might + * skip locking if process appears single-threaded. */ + if (!--libc.threads_minus_1) libc.need_locks = -1; + self->next->prev = self->prev; + self->prev->next = self->next; + self->prev = self->next = self; + + if (state==DT_DETACHED && self->map_base) { + /* Detached threads must block even implementation-internal + * signals, since they will not have a stack in their last + * moments of existence. */ + __block_all_sigs(&set); + + /* 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)); /* The following call unmaps the thread's stack mapping * and then exits without touching the stack. */ __unmapself(self->map_base, self->map_size); } + /* Wake any joiner. */ + a_store(&self->detach_state, DT_EXITED); + __wake(&self->detach_state, 1, 1); + for (;;) __syscall(SYS_exit, 0); } void __do_cleanup_push(struct __ptcb *cb) { - if (!libc.has_thread_pointer) return; struct pthread *self = __pthread_self(); cb->__next = self->cancelbuf; self->cancelbuf = cb; @@ -85,37 +181,50 @@ void __do_cleanup_push(struct __ptcb *cb) void __do_cleanup_pop(struct __ptcb *cb) { - if (!libc.has_thread_pointer) return; __pthread_self()->cancelbuf = cb->__next; } +struct start_args { + void *(*start_func)(void *); + void *start_arg; + volatile int control; + unsigned long sig_mask[_NSIG/8/sizeof(long)]; +}; + 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); + struct start_args *args = p; + int state = args->control; + if (state) { + if (a_cas(&args->control, 1, 2)==1) + __wait(&args->control, 0, 2, 1); + if (args->control) { + __syscall(SYS_set_tid_address, &args->control); + for (;;) __syscall(SYS_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)); + __syscall(SYS_rt_sigprocmask, SIG_SETMASK, &args->sig_mask, 0, _NSIG/8); + __pthread_exit(args->start_func(args->start_arg)); + return 0; +} + +static int start_c11(void *p) +{ + struct start_args *args = p; + int (*start)(void*) = (int(*)(void*)) args->start_func; + __pthread_exit((void *)(uintptr_t)start(args->start_arg)); return 0; } #define ROUND(x) (((x)+PAGE_SIZE-1)&-PAGE_SIZE) /* pthread_key_create.c overrides this */ -static const size_t dummy = 0; +static volatile size_t dummy = 0; weak_alias(dummy, __pthread_tsd_size); -static void *const dummy_tsd[1] = { 0 }; +static void *dummy_tsd[1] = { 0 }; weak_alias(dummy_tsd, __pthread_tsd_main); -static FILE *const dummy_file = 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); @@ -125,39 +234,43 @@ 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 __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp, void *(*entry)(void *), void *restrict arg) { - int ret; + 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}; + pthread_attr_t attr = { 0 }; + sigset_t set; if (!libc.can_do_threads) return ENOSYS; self = __pthread_self(); if (!libc.threaded) { - for (FILE *f=libc.ofl_head; f; f=f->next) + 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; + __membarrier_init(); libc.threaded = 1; } - if (attrp) attr = *attrp; + if (attrp && !c11) attr = *attrp; __acquire_ptc(); + if (!attrp || c11) { + attr._a_stacksize = __default_stacksize; + attr._a_guardsize = __default_guardsize; + } if (attr._a_stackaddr) { size_t need = libc.tls_size + __pthread_tsd_size; - size = attr._a_stacksize + DEFAULT_STACK_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 @@ -166,26 +279,28 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp 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; } + guard = 0; } else { - guard = ROUND(DEFAULT_GUARD_SIZE + attr._a_guardsize); - size = guard + ROUND(DEFAULT_STACK_SIZE + attr._a_stacksize + 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); + 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)) { - munmap(map, size); + 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); + 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; @@ -200,44 +315,75 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp new->map_size = size; new->stack = stack; new->stack_size = stack - stack_limit; - new->pid = self->pid; - new->errno_ptr = &new->errno_val; - new->start = entry; - new->start_arg = arg; + new->guard_size = guard; 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->detach_state = DT_DETACHED; + } else { + new->detach_state = DT_JOINABLE; } - new->unblock_cancel = self->cancel; + new->robust_list.head = &new->robust_list.head; new->canary = self->canary; - - a_inc(&libc.threads_minus_1); - ret = __clone(start, stack, flags, new, &new->tid, TP_ADJ(new), &new->tid); - - __release_ptc(); - - if (do_sched) { - __restore_sigs(new->sigmask); + new->sysinfo = self->sysinfo; + + /* Setup argument structure for the new thread on its stack. + * It's safe to access from the caller only until the thread + * list is unlocked. */ + stack -= (uintptr_t)stack % sizeof(uintptr_t); + stack -= sizeof(struct start_args); + struct start_args *args = (void *)stack; + args->start_func = entry; + args->start_arg = arg; + args->control = attr._a_sched ? 1 : 0; + + /* Application signals (but not the synccall signal) must be + * blocked before the thread list lock can be taken, to ensure + * that the lock is AS-safe. */ + __block_app_sigs(&set); + + /* Ensure SIGCANCEL is unblocked in new thread. This requires + * working with a copy of the set so we can restore the + * original mask in the calling thread. */ + memcpy(&args->sig_mask, &set, sizeof args->sig_mask); + args->sig_mask[(SIGCANCEL-1)/8/sizeof(long)] &= + ~(1UL<<((SIGCANCEL-1)%(8*sizeof(long)))); + + __tl_lock(); + if (!libc.threads_minus_1++) libc.need_locks = 1; + ret = __clone((c11 ? start_c11 : start), stack, flags, args, &new->tid, TP_ADJ(new), &__thread_list_lock); + + /* All clone failures translate to EAGAIN. If explicit scheduling + * was requested, attempt it before unlocking the thread list so + * that the failed thread is never exposed and so that we can + * clean up all transient resource usage before returning. */ + if (ret < 0) { + ret = -EAGAIN; + } else if (attr._a_sched) { + ret = __syscall(SYS_sched_setscheduler, + new->tid, attr._a_policy, &attr._a_prio); + if (a_swap(&args->control, ret ? 3 : 0)==2) + __wake(&args->control, 1, 1); + if (ret) + __wait(&args->control, 0, 3, 0); } - if (ret < 0) { - a_dec(&libc.threads_minus_1); - if (map) munmap(map, size); - return EAGAIN; + if (ret >= 0) { + new->next = self->next; + new->prev = self; + new->next->prev = new; + new->prev->next = new; + } else { + if (!--libc.threads_minus_1) libc.need_locks = 0; } + __tl_unlock(); + __restore_sigs(&set); + __release_ptc(); - 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; + if (ret < 0) { + if (map) __munmap(map, size); + return -ret; } *res = new; @@ -246,3 +392,6 @@ fail: __release_ptc(); return EAGAIN; } + +weak_alias(__pthread_exit, pthread_exit); +weak_alias(__pthread_create, pthread_create);