From 69c834c081d7e7ce063ee6b2bbad85b849680bf4 Mon Sep 17 00:00:00 2001
From: Roavin <chris.r.walton@gmail.com>
Date: Sun, 9 Feb 2025 22:27:27 +0100
Subject: [PATCH 1/2] Ensure MySQL is only initialized once

---
 dbdimp.c | 17 ++++++++++++++++-
 dbdimp.h |  2 +-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/dbdimp.c b/dbdimp.c
index 39db0336..35ebaabc 100644
--- a/dbdimp.c
+++ b/dbdimp.c
@@ -57,6 +57,21 @@ 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 in Apache MPM workers.
+*/ 
+pthread_once_t once_mysql_initialized = PTHREAD_ONCE_INIT;
+
+static void init_mysql_library(void)
+{
+  mysql_library_init(0, NULL, NULL);
+}
+
+static void ensure_mysql_initialized()
+{
+  pthread_once(&once_mysql_initialized, init_mysql_library);
+}
 
 /*
 
@@ -1206,7 +1221,7 @@ 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)
diff --git a/dbdimp.h b/dbdimp.h
index 3d8c76b6..ec208da6 100644
--- a/dbdimp.h
+++ b/dbdimp.h
@@ -22,7 +22,7 @@
 #include <mysql.h>  /* Comes with MySQL-devel */
 #include <mysqld_error.h>  /* Comes MySQL */
 #include <errmsg.h> /* Comes with MySQL-devel */
-
+#include <pthread.h>
 
 #define true 1
 #define false 0

From 1d09c3f6951aa82fedce0adcedd154cc01a840c9 Mon Sep 17 00:00:00 2001
From: Roavin <chris.r.walton@gmail.com>
Date: Fri, 21 Feb 2025 17:27:57 +0100
Subject: [PATCH 2/2] Add Win32 init path

---
 Makefile.PL | 10 ++++++++++
 dbdimp.c    | 45 ++++++++++++++++++++++++++++++++++++++++++---
 dbdimp.h    |  1 -
 3 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/Makefile.PL b/Makefile.PL
index 3d707231..c3abe11f 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -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/) {
+    $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",
diff --git a/dbdimp.c b/dbdimp.c
index 35ebaabc..470a9b61 100644
--- a/dbdimp.c
+++ b/dbdimp.c
@@ -59,20 +59,59 @@ typedef struct sql_type_info_s
 
 /*
   Ensure we only call mysql_library_init once, since that is not threadsafe.
-  Not doing this before had lead to crashes in Apache MPM workers.
+  Not doing this before had lead to crashes and deadlocks in Apache MPM workers.
 */ 
-pthread_once_t once_mysql_initialized = PTHREAD_ONCE_INIT;
 
 static void init_mysql_library(void)
 {
   mysql_library_init(0, NULL, NULL);
 }
 
-static void ensure_mysql_initialized()
+#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
+
 /*
 
   This function manually counts the number of placeholders in an SQL statement,
diff --git a/dbdimp.h b/dbdimp.h
index ec208da6..c08142ab 100644
--- a/dbdimp.h
+++ b/dbdimp.h
@@ -22,7 +22,6 @@
 #include <mysql.h>  /* Comes with MySQL-devel */
 #include <mysqld_error.h>  /* Comes MySQL */
 #include <errmsg.h> /* Comes with MySQL-devel */
-#include <pthread.h>
 
 #define true 1
 #define false 0