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Bug #45058 init_available_charsets uses double checked locking

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As documented in the bug report, the double checked locking
pattern has inherent issues, and cannot guarantee correct
initialization.

This patch replaces the logic in init_available_charsets()
with the use of pthread_once(3). A wrapper function,
my_pthread_once(), is introduced and is used in lieu of direct
calls to init_available_charsets(). Related defines
MY_PTHREAD_ONCE_* are also introduced.

For the Windows platform, the implementation in lp:sysbench is
ported. For single-thread use, a simple define calls the
function and sets the pthread_once control variable.

Charset initialization is modified to use my_pthread_once().

include/my_no_pthread.h:
  Dummy my_pthread_once() for single thread use.
include/my_pthread.h:
  Declaration for new function my_pthread_once().
mysys/charset.c:
  Logic in init_available_charsets() is simplified. 
  Using my_pthread_once() for all calls to this func.
mysys/my_winthread.c:
  Windows implementation of my_pthread_once().
This commit is contained in:
Staale Smedseng
2009-12-12 19:11:25 +01:00
parent 0654e74a70
commit 8969530cff
9 changed files with 77 additions and 58 deletions
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10
include/my_pthread.h
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@@ -69,6 +69,11 @@ typedef int pthread_mutexattr_t;
#define pthread_handler_t EXTERNC void * __cdecl
typedef void * (__cdecl *pthread_handler)(void *);
typedef volatile LONG my_pthread_once_t;
#define MY_PTHREAD_ONCE_INIT 0
#define MY_PTHREAD_ONCE_INPROGRESS 1
#define MY_PTHREAD_ONCE_DONE 2
/*
Struct and macros to be used in combination with the
windows implementation of pthread_cond_timedwait
@@ -114,6 +119,7 @@ int pthread_attr_init(pthread_attr_t *connect_att);
int pthread_attr_setstacksize(pthread_attr_t *connect_att,DWORD stack);
int pthread_attr_setprio(pthread_attr_t *connect_att,int priority);
int pthread_attr_destroy(pthread_attr_t *connect_att);
int my_pthread_once(my_pthread_once_t *once_control,void (*init_routine)(void));
struct tm *localtime_r(const time_t *timep,struct tm *tmp);
struct tm *gmtime_r(const time_t *timep,struct tm *tmp);
@@ -210,6 +216,10 @@ extern int my_pthread_getprio(pthread_t thread_id);
#define pthread_handler_t EXTERNC void *
typedef void *(* pthread_handler)(void *);
#define my_pthread_once_t pthread_once_t
#define MY_PTHREAD_ONCE_INIT PTHREAD_ONCE_INIT
#define my_pthread_once(C,F) pthread_once(C,F)
/* Test first for RTS or FSU threads */
#if defined(PTHREAD_SCOPE_GLOBAL) && !defined(PTHREAD_SCOPE_SYSTEM)