From a1cd1984ae2a588b102a3102a199a5404e3686dd Mon Sep 17 00:00:00 2001
From: Yann Ylavic <ylavic@apache.org>
Date: Thu, 15 Mar 2018 23:15:49 +0000
Subject: [PATCH] Merge r1826845 from trunk:

mod_slotmem_shm: SHMs need to be attached in MPM winnt children processes.

We can't (re-)create them since they exist already and are owned by the
parent process.


Submitted by: ylavic
Reviewed by: ylavic, covener, rjung


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1826897 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES                           |  4 +++
 modules/slotmem/mod_slotmem_shm.c | 48 +++++++++++++++++++++++++++----
 2 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/CHANGES b/CHANGES
index da634c676f..07dea06a1f 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,10 @@
                                                          -*- coding: utf-8 -*-
 Changes with Apache 2.4.33
 
+  *) mod_slomem_shm: Fix failure to create balancers's slotmems in Windows MPM,
+     where children processes need to attach them instead since they are owned
+     by the parent process already.  [Yann Ylavic]
+
   *) ab: try all destination socket addresses returned by
      apr_sockaddr_info_get instead of failing on first one when not available.
      Needed for instance if localhost resolves to both ::1 and 127.0.0.1
diff --git a/modules/slotmem/mod_slotmem_shm.c b/modules/slotmem/mod_slotmem_shm.c
index e7599726d4..681515aa19 100644
--- a/modules/slotmem/mod_slotmem_shm.c
+++ b/modules/slotmem/mod_slotmem_shm.c
@@ -274,11 +274,30 @@ static apr_status_t restore_slotmem(sharedslotdesc_t *desc,
     return rv;
 }
 
+/*
+ * Whether the module is called from a MPM that re-enter main() and
+ * pre/post_config phases.
+ */
+static APR_INLINE int is_child_process(void)
+{
+#ifdef WIN32
+    return getenv("AP_PARENT_PID") != NULL;
+#else
+    return 0;
+#endif
+}
+
 static apr_status_t cleanup_slotmem(void *is_startup)
 {
     int is_exiting = (ap_state_query(AP_SQ_MAIN_STATE) == AP_SQ_MS_EXITING);
     ap_slotmem_instance_t *mem;
 
+    if (is_child_process()) {
+        /* No reuse/retained data from here, let pconf cleanup everything */
+        *retained_globallistmem = globallistmem = NULL;
+        return APR_SUCCESS;
+    }
+
     /* When in startup/pre-config's cleanup, the retained data and global pool
      * are not used yet, but the SHMs contents were untouched hence they don't
      * need to be persisted, simply unlink them.
@@ -439,17 +458,26 @@ static apr_status_t slotmem_create(ap_slotmem_instance_t **new,
 
     {
         if (fbased) {
-            apr_shm_remove(fname, pool);
-            rv = apr_shm_create(&shm, size, fname, gpool);
+            /* For MPMs (e.g. winnt) that run pre/post_config() phases in
+             * both the parent and children processes, SHMs created by the
+             * parent exist in the children already; only attach them.
+             */
+            if (is_child_process()) {
+                rv = apr_shm_attach(&shm, fname, gpool);
+            }
+            else {
+                apr_shm_remove(fname, pool);
+                rv = apr_shm_create(&shm, size, fname, gpool);
+            }
         }
         else {
             rv = apr_shm_create(&shm, size, NULL, pool);
         }
         ap_log_error(APLOG_MARK, rv == APR_SUCCESS ? APLOG_DEBUG : APLOG_ERR,
                      rv, ap_server_conf, APLOGNO(02611)
-                     "create: apr_shm_create(%s) %s",
-                     fname ? fname : "",
-                     rv == APR_SUCCESS ? "succeeded" : "failed");
+                     "create: apr_shm_%s(%s) %s",
+                     fbased && is_child_process() ? "attach" : "create",
+                     fname, rv == APR_SUCCESS ? "succeeded" : "failed");
         if (rv != APR_SUCCESS) {
             return rv;
         }
@@ -811,7 +839,15 @@ static int pre_config(apr_pool_t *pconf, apr_pool_t *plog,
     }
     globallistmem = *retained_globallistmem;
 
-    if (ap_state_query(AP_SQ_MAIN_STATE) != AP_SQ_MS_CREATE_PRE_CONFIG) {
+    /* For the first (dry-)loading or children in MPMs which (re-)run
+     * pre_config we don't need to retain slotmems, so use pconf and its
+     * normal cleanups. Otherwise we use ap_pglobal to match the lifetime
+     * of retained data and register our own cleanup to update them.
+     */
+    if (is_child_process()) {
+        gpool = pconf;
+    }
+    else if (ap_state_query(AP_SQ_MAIN_STATE) != AP_SQ_MS_CREATE_PRE_CONFIG) {
         gpool = ap_pglobal;
     }
     else {
-- 
2.40.0