src/thread/pthread_key_create.c - master - clang/musl

src/thread/pthread_key_create.c
99 строк2 KB
Rich Felker
fix missing synchronization of pthread TSD keys with MT-fork
19 окт 2022, 21:01
19 окт 2022, 21:01cf76df0
#include "pthread_impl.h"
#include "fork_impl.h"

volatile size_t __pthread_tsd_size = sizeof(void *) * PTHREAD_KEYS_MAX;
void *__pthread_tsd_main[PTHREAD_KEYS_MAX] = { 0 };

static void (*keys[PTHREAD_KEYS_MAX])(void *);

static pthread_rwlock_t key_lock = PTHREAD_RWLOCK_INITIALIZER;

static pthread_key_t next_key;

static void nodtor(void *dummy)
{
}

static void dummy_0(void)
{
}

weak_alias(dummy_0, __tl_lock);
weak_alias(dummy_0, __tl_unlock);

void __pthread_key_atfork(int who)
{
	if (who<0) __pthread_rwlock_rdlock(&key_lock);
	else if (!who) __pthread_rwlock_unlock(&key_lock);
	else key_lock = (pthread_rwlock_t)PTHREAD_RWLOCK_INITIALIZER;
}

int __pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
{
	pthread_t self = __pthread_self();

	/* This can only happen in the main thread before
	 * pthread_create has been called. */
	if (!self->tsd) self->tsd = __pthread_tsd_main;

	/* Purely a sentinel value since null means slot is free. */
	if (!dtor) dtor = nodtor;

	__pthread_rwlock_wrlock(&key_lock);
	pthread_key_t j = next_key;
	do {
		if (!keys[j]) {
			keys[next_key = *k = j] = dtor;
			__pthread_rwlock_unlock(&key_lock);
			return 0;
		}
	} while ((j=(j+1)%PTHREAD_KEYS_MAX) != next_key);

	__pthread_rwlock_unlock(&key_lock);
	return EAGAIN;
}

int __pthread_key_delete(pthread_key_t k)
{
	sigset_t set;
	pthread_t self = __pthread_self(), td=self;

	__block_app_sigs(&set);
	__pthread_rwlock_wrlock(&key_lock);

	__tl_lock();
	do td->tsd[k] = 0;
	while ((td=td->next)!=self);
	__tl_unlock();

	keys[k] = 0;

	__pthread_rwlock_unlock(&key_lock);
	__restore_sigs(&set);

	return 0;
}

void __pthread_tsd_run_dtors()
{
	pthread_t self = __pthread_self();
	int i, j;
	for (j=0; self->tsd_used && j<PTHREAD_DESTRUCTOR_ITERATIONS; j++) {
		__pthread_rwlock_rdlock(&key_lock);
		self->tsd_used = 0;
		for (i=0; i<PTHREAD_KEYS_MAX; i++) {
			void *val = self->tsd[i];
			void (*dtor)(void *) = keys[i];
			self->tsd[i] = 0;
			if (val && dtor && dtor != nodtor) {
				__pthread_rwlock_unlock(&key_lock);
				dtor(val);
				__pthread_rwlock_rdlock(&key_lock);
			}
		}
		__pthread_rwlock_unlock(&key_lock);
	}
}

weak_alias(__pthread_key_create, pthread_key_create);
weak_alias(__pthread_key_delete, pthread_key_delete);