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implement our own "once" function #2086

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merged 4 commits into from Jul 22, 2019
Merged

implement our own "once" function #2086

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4577653
implement H2O_MULTITHREAD_ONCE
kazuho Jul 22, 2019
9c06f68
use H2O_MULTITHREAD_ONCE
kazuho Jul 22, 2019
f235be7
we need volatile too, to avoid the compiler moving load before a barrier
kazuho Jul 22, 2019
d0a0e6e
fix typo
kazuho Jul 22, 2019
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22 changes: 22 additions & 0 deletions include/h2o/multithread.h
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Expand Up @@ -82,6 +82,28 @@ void h2o_multithread_send_message(h2o_multithread_receiver_t *receiver, h2o_mult
*/
void h2o_multithread_create_thread(pthread_t *tid, const pthread_attr_t *attr, void *(*func)(void *), void *arg);

/**
* a variant of pthread_once, that does not require you to declare a callback, nor have a global variable
*/
#define H2O_MULTITHREAD_ONCE(block) \
do { \
static volatile int lock = 0; \
int lock_loaded = lock; \
__sync_synchronize(); \
if (!lock_loaded) { \
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; \
pthread_mutex_lock(&mutex); \
if (!lock) { \
do { \
block \
} while (0); \
__sync_synchronize(); \
lock = 1; \
} \
pthread_mutex_unlock(&mutex); \
} \
} while (0)

void h2o_sem_init(h2o_sem_t *sem, ssize_t capacity);
void h2o_sem_destroy(h2o_sem_t *sem);
void h2o_sem_wait(h2o_sem_t *sem);
Expand Down
48 changes: 13 additions & 35 deletions lib/common/socket.c
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Expand Up @@ -37,6 +37,7 @@
#include "picotls.h"
#endif
#include "h2o/socket.h"
#include "h2o/multithread.h"

#if defined(__APPLE__) && defined(__clang__)
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
Expand Down Expand Up @@ -211,21 +212,14 @@ static long ctrl_bio(BIO *b, int cmd, long num, void *ptr)

static void setup_bio(h2o_socket_t *sock)
{
static BIO_METHOD *bio_methods = NULL;
if (bio_methods == NULL) {
static pthread_mutex_t init_lock = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&init_lock);
if (bio_methods == NULL) {
BIO_METHOD *biom = BIO_meth_new(BIO_TYPE_FD, "h2o_socket");
BIO_meth_set_write(biom, write_bio);
BIO_meth_set_read(biom, read_bio);
BIO_meth_set_puts(biom, puts_bio);
BIO_meth_set_ctrl(biom, ctrl_bio);
__sync_synchronize();
bio_methods = biom;
}
pthread_mutex_unlock(&init_lock);
}
static volatile BIO_METHOD *bio_methods = NULL;
H2O_MULTITHREAD_ONCE({
bio_methods = BIO_meth_new(BIO_TYPE_FD, "h2o_socket");
BIO_meth_set_write(bio_methods, write_bio);
BIO_meth_set_read(bio_methods, read_bio);
BIO_meth_set_puts(bio_methods, puts_bio);
BIO_meth_set_ctrl(bio_methods, ctrl_bio);
});

BIO *bio = BIO_new(bio_methods);
if (bio == NULL)
Expand Down Expand Up @@ -1308,18 +1302,8 @@ void h2o_socket_ssl_async_resumption_setup_ctx(SSL_CTX *ctx)

static int get_ptls_index(void)
{
static int index = -1;

if (index == -1) {
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&mutex);
if (index == -1) {
index = SSL_CTX_get_ex_new_index(0, NULL, NULL, NULL, NULL);
assert(index != -1);
}
pthread_mutex_unlock(&mutex);
}

static volatile int index;
H2O_MULTITHREAD_ONCE({ index = SSL_CTX_get_ex_new_index(0, NULL, NULL, NULL, NULL); });
return index;
}

Expand All @@ -1344,14 +1328,8 @@ static void on_dispose_ssl_ctx_session_cache(void *parent, void *ptr, CRYPTO_EX_

static int get_ssl_session_cache_index(void)
{
static int index = -1;
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&mutex);
if (index == -1) {
index = SSL_CTX_get_ex_new_index(0, NULL, NULL, NULL, on_dispose_ssl_ctx_session_cache);
assert(index != -1);
}
pthread_mutex_unlock(&mutex);
static volatile int index;
H2O_MULTITHREAD_ONCE({ index = SSL_CTX_get_ex_new_index(0, NULL, NULL, NULL, on_dispose_ssl_ctx_session_cache); });
return index;
}

Expand Down