Re: [PATCH] fix libpq mutex initialization for multithreaded

Patch applied. Thanks.

---------------------------------------------------------------------------

Manfred Spraul wrote:
> Hi,
>
> win32 doesn't support a static initializer for mutexes, thus the first
> user must initialize the lock. The problem are concurrent "first" users
> - the pthread_mutex_t initialization must be synchronized.
> The current implementation is broken, the attached patches fixes that:
> mutex_initlock is a spinlock. If the pthread_mutex_t mutex is not
> initialized, then the spinlock is acquired, if the pthread_mutex_t is
> initialized if it's not yet initialized and then the spinlock is dropped.
>
> Again untested due to lack of Visual C++.
>
> --
> Manfre

> ? GNUmakefile
> ? config.log
> ? config.status
> ? src/Makefile.global
> ? src/include/pg_config.h
> ? src/include/stamp-h
> ? src/port/pg_config_paths.h
> Index: src/interfaces/libpq/fe-connect.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/fe-connect.c,v
> retrieving revision 1.275
> diff -c -r1.275 fe-connect.c
> *** src/interfaces/libpq/fe-connect.c 19 Jun 2004 04:22:17 -0000 1.275
> --- src/interfaces/libpq/fe-connect.c 20 Jun 2004 16:38:38 -0000
> ***************
> *** 3193,3202 ****
> #ifndef WIN32
> static pthread_mutex_t singlethread_lock = PTHREAD_MUTEX_INITIALIZER;
> #else
> ! static pthread_mutex_t singlethread_lock;
> ! static long mutex_initialized = 0;
> ! if (!InterlockedExchange(&mutex_initialized, 1L))
> ! pthread_mutex_init(&singlethread_lock, NULL);
> #endif
> if (acquire)
> pthread_mutex_lock(&singlethread_lock);
> --- 3193,3208 ----
> #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)
> ! pthread_mutex_init(&singlethread_lock, NULL);
> ! InterlockedExchange(&mutex_initlock,0);
> ! }
> #endif
> if (acquire)
> pthread_mutex_lock(&singlethread_lock);
> Index: src/interfaces/libpq/fe-secure.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/fe-secure.c,v
> retrieving revision 1.42
> diff -c -r1.42 fe-secure.c
> *** src/interfaces/libpq/fe-secure.c 19 Jun 2004 04:22:17 -0000 1.42
> --- src/interfaces/libpq/fe-secure.c 20 Jun 2004 16:38:39 -0000
> ***************
> *** 867,876 ****
> #ifndef WIN32
> static pthread_mutex_t init_mutex = PTHREAD_MUTEX_INITIALIZER;
> #else
> ! static pthread_mutex_t init_mutex;
> ! static long mutex_initialized = 0L;
> ! if (!InterlockedExchange(&mutex_initialized, 1L))
> ! pthread_mutex_init(&init_mutex, NULL);
> #endif
> pthread_mutex_lock(&init_mutex);
>
> --- 867,882 ----
> #ifndef WIN32
> static pthread_mutex_t init_mutex = PTHREAD_MUTEX_INITIALIZER;
> #else
> ! static pthread_mutex_t init_mutex = NULL;
> ! static long mutex_initlock = 0;
> !
> ! if (init_mutex == NULL) {
> ! while(InterlockedExchange(&mutex_initlock, 1) == 1)
> ! /* loop, another thread own the lock */ ;
> ! if (init_mutex == NULL)
> ! pthread_mutex_init(&init_mutex, NULL);
> ! InterlockedExchange(&mutex_initlock,0);
> ! }
> #endif
> pthread_mutex_lock(&init_mutex);
>

>
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