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Ensure MySQL is only initialized once #465

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Ensure MySQL is only initialized once #465

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69c834c
Ensure MySQL is only initialized once
roavin Feb 9, 2025
1d09c3f
Add Win32 init path
roavin Feb 21, 2025
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10 changes: 10 additions & 0 deletions Makefile.PL
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Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,16 @@ if ($^O eq 'VMS') {
}
$cflags .= " -DDBD_MYSQL_NO_CLIENT_FOUND_ROWS" if $opt->{'nofoundrows'};
$cflags .= " -g ";

unless ($^O eq 'MSWin32') {
if ($Config{usethreads} || $Config{osname} =~ /darwin|linux/i || $Config{libs} =~ /-l?pthread\b/ || $Config{ldflags} =~ /-l?pthread\b/) {
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I'm not sure this condition is correct, as it will assume that any mac or linux install has pthreads which is not true?

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Though I see that is also done in the condition I linked to, seems strange.

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Yes, that's why I did it that way. I can imagine that OSX systems generally have pthreads and I suppose the thinking for Linux is that pretty much any system not older than 2 decades will have pthreads there too.

$cflags .= " -DDBD_MYSQL_HAS_PTHREADS";
} else {
print "*** This module may crash or deadlock on startup in multi-threaded scenarios ***\n",
" To avoid this, make sure your Perl is compiled with pthreads.\n\n",
}
}

my %o = ( 'NAME' => 'DBD::mysql',
'INC' => $cflags,
'dist'=> { 'SUFFIX' => ".gz",
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56 changes: 55 additions & 1 deletion dbdimp.c
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Expand Up @@ -57,6 +57,60 @@ typedef struct sql_type_info_s
int is_num;
} sql_type_info_t;

/*
Ensure we only call mysql_library_init once, since that is not threadsafe.
Not doing this before had lead to crashes and deadlocks in Apache MPM workers.
*/

static void init_mysql_library(void)
{
mysql_library_init(0, NULL, NULL);
}

#ifdef DBD_MYSQL_HAS_PTHREADS

#include <pthread.h>
static pthread_once_t once_mysql_initialized = PTHREAD_ONCE_INIT;

static void ensure_mysql_initialized(void)
{
pthread_once(&once_mysql_initialized, init_mysql_library);
}

#elif defined(_WIN32)

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
static INIT_ONCE once_mysql_initialized = INIT_ONCE_STATIC_INIT;

static BOOL init_mysql_library_thunk(PINIT_ONCE once, PVOID param, PVOID *context)
{
init_mysql_library();
return TRUE;
}

static void ensure_mysql_initialized(void)
{
InitOnceExecuteOnce(&once_mysql_initialized, init_mysql_library_thunk, NULL, NULL);
}

#else
static int is_mysql_initialized = 0;

static void ensure_mysql_initialized(void)
{
/* Thread-unsafe fallback
* In practice, this will only be used for perls not compiled with threads
* anyway, so it's very unlikely that this would be a problem.
*/
if (!is_mysql_initialized)
{
is_mysql_initialized = 1;
mysql_library_init(0, NULL, NULL);
}
}

#endif

/*

Expand Down Expand Up @@ -1206,7 +1260,7 @@ MYSQL *mysql_dr_connect(
#else
client_flag = CLIENT_FOUND_ROWS;
#endif
mysql_library_init(0, NULL, NULL);
ensure_mysql_initialized();
mysql_init(sock);

if (imp_dbh)
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1 change: 0 additions & 1 deletion dbdimp.h
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Expand Up @@ -23,7 +23,6 @@
#include <mysqld_error.h> /* Comes MySQL */
#include <errmsg.h> /* Comes with MySQL-devel */


#define true 1
#define false 0

Expand Down