From 9f041b041feb3361748496e5813cd3a5b034361c Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 9 Feb 2024 11:11:39 -0500 Subject: [PATCH] Clean up Windows-specific mutex code in libpq and ecpglib. 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. Also, replace the similar code in ecpglib/misc.c with this version. While ecpglib's version at least had a POSIX-compliant API, it also had the potential of failing during mutex init (but here, because of CreateMutex failure rather than malloc failure). Since all of misc.c's callers ignore failures, it seems like a wise idea to avoid failures here too. A further improvement in this area could be to unify libpq's and ecpglib's implementations into a src/port/pthread-win32.c file. But that doesn't seem like a bug fix, so I'll desist for now. In preparation for the aforementioned bug fix, back-patch to all supported branches. Discussion: https://postgr.es/m/264860.1707163416@sss.pgh.pa.us --- src/interfaces/ecpg/ecpglib/misc.c | 37 +++++++++++++++---- .../ecpg/include/ecpg-pthread-win32.h | 22 ++++------- 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 +++++- 6 files changed, 63 insertions(+), 69 deletions(-) diff --git a/src/interfaces/ecpg/ecpglib/misc.c b/src/interfaces/ecpg/ecpglib/misc.c index 1eef1ec044..68fc627f10 100644 --- a/src/interfaces/ecpg/ecpglib/misc.c +++ b/src/interfaces/ecpg/ecpglib/misc.c @@ -453,17 +453,38 @@ ECPGis_noind_null(enum ECPGttype type, const void *ptr) #ifdef WIN32 #ifdef ENABLE_THREAD_SAFETY -void -win32_pthread_mutex(volatile pthread_mutex_t *mutex) +int +pthread_mutex_init(pthread_mutex_t *mp, void *attr) { - if (mutex->handle == NULL) + mp->initstate = 0; + return 0; +} + +int +pthread_mutex_lock(pthread_mutex_t *mp) +{ + /* Initialize the csection if not already done */ + if (mp->initstate != 1) { - while (InterlockedExchange((LONG *) &mutex->initlock, 1) == 1) - Sleep(0); - if (mutex->handle == NULL) - mutex->handle = CreateMutex(NULL, FALSE, NULL); - InterlockedExchange((LONG *) &mutex->initlock, 0); + 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->initstate != 1) + return EINVAL; + LeaveCriticalSection(&mp->csection); + return 0; } static pthread_mutex_t win32_pthread_once_lock = PTHREAD_MUTEX_INITIALIZER; diff --git a/src/interfaces/ecpg/include/ecpg-pthread-win32.h b/src/interfaces/ecpg/include/ecpg-pthread-win32.h index 33c897b633..2782e49d4c 100644 --- a/src/interfaces/ecpg/include/ecpg-pthread-win32.h +++ b/src/interfaces/ecpg/include/ecpg-pthread-win32.h @@ -14,29 +14,23 @@ typedef struct pthread_mutex_t { - HANDLE handle; - LONG initlock; + /* initstate = 0: not initialized; 1: init done; 2: init in progress */ + LONG initstate; + CRITICAL_SECTION csection; } pthread_mutex_t; typedef DWORD pthread_key_t; typedef bool pthread_once_t; -#define PTHREAD_MUTEX_INITIALIZER { NULL, 0 } +#define PTHREAD_MUTEX_INITIALIZER { 0 } #define PTHREAD_ONCE_INIT false -void win32_pthread_mutex(volatile pthread_mutex_t *mutex); +int pthread_mutex_init(pthread_mutex_t *, void *attr); +int pthread_mutex_lock(pthread_mutex_t *); +int pthread_mutex_unlock(pthread_mutex_t *); + void win32_pthread_once(volatile pthread_once_t *once, void (*fn) (void)); -#define pthread_mutex_lock(mutex) \ - do { \ - if ((mutex)->handle == NULL) \ - win32_pthread_mutex((mutex)); \ - WaitForSingleObject((mutex)->handle, INFINITE); \ - } while(0) - -#define pthread_mutex_unlock(mutex) \ - ReleaseMutex((mutex)->handle) - #define pthread_getspecific(key) \ TlsGetValue((key)) diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index a80901349b..47dcb37fd4 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -7443,24 +7443,8 @@ static void default_threadlock(int acquire) { #ifdef ENABLE_THREAD_SAFETY -#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 61f37678a6..1c9dd76bea 100644 --- a/src/interfaces/libpq/fe-secure-openssl.c +++ b/src/interfaces/libpq/fe-secure-openssl.c @@ -96,12 +96,7 @@ static bool ssl_lib_initialized = false; #ifdef ENABLE_THREAD_SAFETY 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 #endif /* ENABLE_THREAD_SAFETY */ static PQsslKeyPassHook_OpenSSL_type PQsslKeyPassHook = NULL; @@ -777,20 +772,6 @@ int pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto) { #ifdef ENABLE_THREAD_SAFETY -#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; @@ -881,7 +862,6 @@ static void destroy_ssl_system(void) { #if defined(ENABLE_THREAD_SAFETY) && 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 c0e056ea21..c9609c0581 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);