#define _GNU_SOURCE
#include "pthread_impl.h"
#include "stdio_impl.h"
#include "libc.h"
#include "lock.h"
#include <sys/mman.h>
#include <string.h>
#include <stddef.h>
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);
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) {
void (*f)(void *) = self->cancelbuf->__f;
void *x = self->cancelbuf->__x;
self->cancelbuf = self->cancelbuf->__next;
f(x);
}
__pthread_tsd_run_dtors();
/* 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. */
__block_app_sigs(&set);
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);
__restore_sigs(&set);
exit(0);
}
/* At this point we are committed to thread termination. */
/* 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;
/* 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) {
/* 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));
/* 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);
}
/* Wake any joiner. */
__wake(&self->detach_state, 1, 1);
/* 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. */
self->tid = 0;
UNLOCK(self->killlock);
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;
}
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)
{
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);
}
}
__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 volatile size_t dummy = 0;
weak_alias(dummy, __pthread_tsd_size);
static void *dummy_tsd[1] = { 0 };
weak_alias(dummy_tsd, __pthread_tsd_main);
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;
}
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;
pthread_attr_t attr = { 0 };
sigset_t set;
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;
__membarrier_init();
libc.threaded = 1;
}
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;
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->guard_size = guard;
new->self = new;
new->tsd = (void *)tsd;
new->locale = &libc.global_locale;
if (attr._a_detach) {
new->detach_state = DT_DETACHED;
} else {
new->detach_state = DT_JOINABLE;
}
new->robust_list.head = &new->robust_list.head;
new->canary = self->canary;
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) {
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 (ret < 0) {
if (map) __munmap(map, size);
return -ret;
}
*res = new;
return 0;
fail:
__release_ptc();
return EAGAIN;
}
weak_alias(__pthread_exit, pthread_exit);
weak_alias(__pthread_create, pthread_create);
