From be34eb602c1e28cb60141e46c79dcadc20933854 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 5 Feb 2024 14:23:20 -0500 Subject: [PATCH v1 1/2] Clean up unnecessarily Windows-dependent code in libpq. Fix pthread-win32.h and pthread-win32.c to provide a more complete emulation of POSIX pthread mutexes: define PTHREAD_MUTEX_INITIALIZER and make sure that pthread_mutex_lock() can operate on a mutex object that's been initialized that way. Then we don't need the duplicative platform-specific logic in default_threadlock() and pgtls_init(), which we'd otherwise need yet a third copy of for an upcoming bug fix. Also, since default_threadlock() supposes that pthread_mutex_lock() cannot fail, try to ensure that that's actually true, by getting rid of the malloc call that was formerly involved in initializing an emulated mutex. We can define an extra state for the spinlock field instead. The idea of making pthread_mutex_t into a struct with a spinlock-like field is borrowed from ecpg's similar emulation. Perhaps we should adopt this implementation there too, since ecpg also contains some presently-bogus assumptions that mutex locking can't fail. --- src/interfaces/libpq/fe-connect.c | 16 --------------- src/interfaces/libpq/fe-secure-openssl.c | 20 ------------------ src/interfaces/libpq/pthread-win32.c | 26 +++++++++++++++--------- src/port/pthread-win32.h | 11 +++++++++- 4 files changed, 26 insertions(+), 47 deletions(-) diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index 64c0b628b3..d4e10a0c4f 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -7426,24 +7426,8 @@ error: static void default_threadlock(int acquire) { -#ifndef WIN32 static pthread_mutex_t singlethread_lock = PTHREAD_MUTEX_INITIALIZER; -#else - static pthread_mutex_t singlethread_lock = NULL; - static long mutex_initlock = 0; - if (singlethread_lock == NULL) - { - while (InterlockedExchange(&mutex_initlock, 1) == 1) - /* loop, another thread own the lock */ ; - if (singlethread_lock == NULL) - { - if (pthread_mutex_init(&singlethread_lock, NULL)) - Assert(false); - } - InterlockedExchange(&mutex_initlock, 0); - } -#endif if (acquire) { if (pthread_mutex_lock(&singlethread_lock)) diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c index 6bc216956d..8110882262 100644 --- a/src/interfaces/libpq/fe-secure-openssl.c +++ b/src/interfaces/libpq/fe-secure-openssl.c @@ -91,12 +91,7 @@ static bool ssl_lib_initialized = false; static long crypto_open_connections = 0; -#ifndef WIN32 static pthread_mutex_t ssl_config_mutex = PTHREAD_MUTEX_INITIALIZER; -#else -static pthread_mutex_t ssl_config_mutex = NULL; -static long win32_ssl_create_mutex = 0; -#endif static PQsslKeyPassHook_OpenSSL_type PQsslKeyPassHook = NULL; static int ssl_protocol_version_to_openssl(const char *protocol); @@ -773,20 +768,6 @@ pq_lockingcallback(int mode, int n, const char *file, int line) int pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto) { -#ifdef WIN32 - /* Also see similar code in fe-connect.c, default_threadlock() */ - if (ssl_config_mutex == NULL) - { - while (InterlockedExchange(&win32_ssl_create_mutex, 1) == 1) - /* loop, another thread own the lock */ ; - if (ssl_config_mutex == NULL) - { - if (pthread_mutex_init(&ssl_config_mutex, NULL)) - return -1; - } - InterlockedExchange(&win32_ssl_create_mutex, 0); - } -#endif if (pthread_mutex_lock(&ssl_config_mutex)) return -1; @@ -874,7 +855,6 @@ static void destroy_ssl_system(void) { #if defined(HAVE_CRYPTO_LOCK) - /* Mutex is created in pgtls_init() */ if (pthread_mutex_lock(&ssl_config_mutex)) return; diff --git a/src/interfaces/libpq/pthread-win32.c b/src/interfaces/libpq/pthread-win32.c index e607bee89a..b40872898d 100644 --- a/src/interfaces/libpq/pthread-win32.c +++ b/src/interfaces/libpq/pthread-win32.c @@ -34,27 +34,33 @@ pthread_getspecific(pthread_key_t key) int pthread_mutex_init(pthread_mutex_t *mp, void *attr) { - *mp = (CRITICAL_SECTION *) malloc(sizeof(CRITICAL_SECTION)); - if (!*mp) - return 1; - InitializeCriticalSection(*mp); + mp->initstate = 0; return 0; } int pthread_mutex_lock(pthread_mutex_t *mp) { - if (!*mp) - return 1; - EnterCriticalSection(*mp); + /* Initialize the csection if not already done */ + if (mp->initstate != 1) + { + LONG istate; + + while ((istate = InterlockedExchange(&mp->initstate, 2)) == 2) + Sleep(0); /* wait, another thread is doing this */ + if (istate != 1) + InitializeCriticalSection(&mp->csection); + InterlockedExchange(&mp->initstate, 1); + } + EnterCriticalSection(&mp->csection); return 0; } int pthread_mutex_unlock(pthread_mutex_t *mp) { - if (!*mp) - return 1; - LeaveCriticalSection(*mp); + if (mp->initstate != 1) + return EINVAL; + LeaveCriticalSection(&mp->csection); return 0; } diff --git a/src/port/pthread-win32.h b/src/port/pthread-win32.h index 97ccc17a12..5f33269057 100644 --- a/src/port/pthread-win32.h +++ b/src/port/pthread-win32.h @@ -5,7 +5,16 @@ #define __PTHREAD_H typedef ULONG pthread_key_t; -typedef CRITICAL_SECTION *pthread_mutex_t; + +typedef struct pthread_mutex_t +{ + /* initstate = 0: not initialized; 1: init done; 2: init in progress */ + LONG initstate; + CRITICAL_SECTION csection; +} pthread_mutex_t; + +#define PTHREAD_MUTEX_INITIALIZER { 0 } + typedef int pthread_once_t; DWORD pthread_self(void); -- 2.39.3