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

diff --git a/src/interfaces/ecpg/ecpglib/misc.c b/src/interfaces/ecpg/ecpglib/misc.c
index 516885dd67e6060ebbda49193302f3f600a965de..c5077a739113c04d0d1eb72eb91dfe2a71e99281 100644 (file)
--- a/src/interfaces/ecpg/ecpglib/misc.c
+++ b/src/interfaces/ecpg/ecpglib/misc.c
@@ -459,17 +459,38 @@ 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)
+{
+       mp->initstate = 0;
+       return 0;
+}
+
+int
+pthread_mutex_lock(pthread_mutex_t *mp)
 {
-       if (mutex->handle == NULL)
+       /* 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 33c897b633c57eda24c2e9dc32eec7f7ffc18a0c..2782e49d4cdf3e9707d8359f0ff19d5231c5e876 100644 (file)
--- a/src/interfaces/ecpg/include/ecpg-pthread-win32.h
+++ b/src/interfaces/ecpg/include/ecpg-pthread-win32.h
@@ -14,28 +14,22 @@
 
 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);
-void           win32_pthread_once(volatile pthread_once_t *once, void (*fn) (void));
+int                    pthread_mutex_init(pthread_mutex_t *, void *attr);
+int                    pthread_mutex_lock(pthread_mutex_t *);
+int                    pthread_mutex_unlock(pthread_mutex_t *);
 
-#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)
+void           win32_pthread_once(volatile pthread_once_t *once, void (*fn) (void));
 
 #define pthread_getspecific(key) \
        TlsGetValue((key))

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 546ef86c22687a0b57118bb11323acc724563e10..14a4e8d48813f548e63fd5fba2cb6dd7ba0468bc 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -7112,24 +7112,8 @@ 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))
-                               PGTHREAD_ERROR("failed to initialize mutex");
-               }
-               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 2dee9323c69c7b8cac9ed1c2ab75f1ea53f8a886..eddefb02eeb1806b2cfe77a83261be4ccc683368 100644 (file)
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -85,12 +85,7 @@ static bool ssl_lib_initialized = false;
 #ifdef ENABLE_THREAD_SAFETY
 static long ssl_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 */
 
 
@@ -649,20 +644,6 @@ int
 pgtls_init(PGconn *conn)
 {
 #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;
 
@@ -747,7 +728,6 @@ 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 21e4142398eca8be724fe977d1402e32275a63de..3b6267e71ddfd1f794d669b5d9cbcc8795698b78 100644 (file)
--- 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 97ccc17a1263c1a1b5381552dbef3c91a3afa901..5f33269057c5af3c688f5b96672e697b599ab45b 100644 (file)
--- 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);