core: Efficient ap_thread_current() when apr_thread_local() is missing.

#define ap_thread_create, ap_thread_current_create and ap_thread_current to
their apr-1.8+ equivalent if available, or implement them using the compiler's
thread_local mechanism if available, or finally provide stubs otherwise.

#define AP_HAS_THREAD_LOCAL to 1 in the two former case or 0 otherwise, while
AP_THREAD_LOCAL is defined to the compiler's keyword iff AP_HAS_THREAD_LOCAL.

Replace all apr_thread_create() calls with ap_thread_create() so that httpd
threads can use ap_thread_current()'s pool data as Thread Local Storage.

Bump MMN minor.

* include/httpd.h():
  Define AP_HAS_THREAD_LOCAL, AP_THREAD_LOCAL (eventually), ap_thread_create(),
  ap_thread_current_create() and ap_thread_current().
  
* server/util.c:
  Implement ap_thread_create(), ap_thread_current_create() and
  ap_thread_current() when APR < 1.8.

* modules/core/mod_watchdog.c, modules/http2/h2_workers.c,
    modules/ssl/mod_ssl_ct.c:
  Use ap_thread_create() instead of apr_thread_create.

* server/main.c:
  Use AP_HAS_THREAD_LOCAL and ap_thread_current_create instead of APR's.

* server/util_pcre.c:
  Use AP_HAS_THREAD_LOCAL and ap_thread_current instead of APR's.

* server/mpm/event/event.c, server/mpm/worker/worker.c,
    server/mpm/prefork/prefork.c:
  Use ap_thread_create() instead of apr_thread_create.
  Create an apr_thread_t/ap_thread_current() for the main chaild thread usable
  at child_init().
  
* server/mpm/winnt/child.c:
  Use ap_thread_create() instead of CreateThread().
  Create an apr_thread_t/ap_thread_current() for the main chaild thread usable



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1897460 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 54 insertions, 2 deletions

diff --git a/include/ap_mmn.h b/include/ap_mmn.h
index 25709472db..6e35c4fee1 100644
--- a/include/ap_mmn.h
+++ b/include/ap_mmn.h
@@ -700,7 +700,9 @@
  *                         add PROXY_WORKER_UDS_PATH_SIZE.
  * 20211221.1 (2.5.1-dev)  Add read_line to scoreboard.
  * 20211221.2 (2.5.1-dev)  Add AGAIN, AP_MPMQ_CAN_AGAIN.
- * 
+ * 20211221.3 (2.5.1-dev)  Add ap_thread_create(), ap_thread_current_create()
+ *                         and ap_thread_current()
+ *
  */
 
 #define MODULE_MAGIC_COOKIE 0x41503235UL /* "AP25" */
@@ -708,7 +710,7 @@
 #ifndef MODULE_MAGIC_NUMBER_MAJOR
 #define MODULE_MAGIC_NUMBER_MAJOR 20211221
 #endif
-#define MODULE_MAGIC_NUMBER_MINOR 2             /* 0...n */
+#define MODULE_MAGIC_NUMBER_MINOR 3             /* 0...n */
 
 /**
  * Determine if the server's current MODULE_MAGIC_NUMBER is at least a
diff --git a/include/httpd.h b/include/httpd.h
index f9f36fee5b..60e8948b87 100644
--- a/include/httpd.h
+++ b/include/httpd.h
@@ -47,6 +47,7 @@
 #include "ap_release.h"
 
 #include "apr.h"
+#include "apr_version.h"
 #include "apr_general.h"
 #include "apr_tables.h"
 #include "apr_pools.h"
@@ -2563,6 +2564,55 @@ AP_DECLARE(void *) ap_realloc(void *ptr, size_t size)
                    AP_FN_ATTR_WARN_UNUSED_RESULT
                    AP_FN_ATTR_ALLOC_SIZE(2);
 
+#if APR_VERSION_AT_LEAST(1,8,0)
+
+/**
+ * APR 1.8+ implement those already.
+ */
+#if APR_HAS_THREAD_LOCAL
+#define AP_HAS_THREAD_LOCAL         1
+#define AP_THREAD_LOCAL             APR_THREAD_LOCAL
+#else
+#define AP_HAS_THREAD_LOCAL         0
+#endif
+#define ap_thread_create            apr_thread_create
+#define ap_thread_current           apr_thread_current
+#define ap_thread_current_create    apr_thread_current_create
+
+#else /* !APR_VERSION_AT_LEAST(1,8,0) */
+
+#if APR_HAS_THREADS
+/**
+ * AP_THREAD_LOCAL keyword mapping the compiler's.
+ */
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#define AP_THREAD_LOCAL thread_local
+#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112
+#define AP_THREAD_LOCAL _Thread_local
+#elif defined(__GNUC__) /* works for clang too */
+#define AP_THREAD_LOCAL __thread
+#elif defined(WIN32) && defined(_MSC_VER)
+#define AP_THREAD_LOCAL __declspec(thread)
+#endif
+#endif /* APR_HAS_THREADS */
+
+#ifndef AP_THREAD_LOCAL
+#define AP_HAS_THREAD_LOCAL 0
+#define ap_thread_create apr_thread_create
+#else /* AP_THREAD_LOCAL */
+#define AP_HAS_THREAD_LOCAL 1
+AP_DECLARE(apr_status_t) ap_thread_create(apr_thread_t **thread, 
+                                          apr_threadattr_t *attr, 
+                                          apr_thread_start_t func, 
+                                          void *data, apr_pool_t *pool);
+#endif /* AP_THREAD_LOCAL */
+AP_DECLARE(apr_status_t) ap_thread_current_create(apr_thread_t **current,
+                                                  apr_threadattr_t *attr,
+                                                  apr_pool_t *pool);
+AP_DECLARE(apr_thread_t *) ap_thread_current(void);
+
+#endif /* !APR_VERSION_AT_LEAST(1,8,0) */
+
 /**
  * Get server load params
  * @param ld struct to populate: -1 in fields means error