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 2b78caeaf5218c602d99de9b07e1249cee805e56..58fff10697d97268fd98979813d3f30d310afb99 100644 (file)
--- a/src/interfaces/ecpg/ecpglib/misc.c
+++ b/src/interfaces/ecpg/ecpglib/misc.c
@@ -407,17 +407,38 @@ ECPGis_noind_null(enum ECPGttype type, const void *ptr)
 
 #ifdef WIN32
 
-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 8252a17809601d9044def7e40270023c3889a1f3..7b6ba46b349b910e2baa64e1501eca0378fdfeb9 100644 (file)
--- a/src/interfaces/ecpg/include/ecpg-pthread-win32.h
+++ b/src/interfaces/ecpg/include/ecpg-pthread-win32.h
@@ -12,28 +12,22 @@
 
 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 64c0b628b3c4af9fd8c2d3eb9ef486875e107d9a..d4e10a0c4f33cb2efe53463db887800f8fa29451 100644 (file)
--- 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 6bc216956d19597b6313a4031ef94ea9cb8cb5a0..811088226200d0ff4f90a42e65ffa7f4e78259df 100644 (file)
--- 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 e607bee89a623dfcedaec04477eab78a676d244f..b40872898d15ea08caa4c7e4458e3af598bef422 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);