From: Jim Jagielski <jim@apache.org>
Date: Fri, 26 Jan 2018 19:49:04 +0000 (+0000)
Subject: PR 62044: Force addition of generation number to shm filename on
X-Git-Tag: 2.5.0-alpha2-ci-test-only~2924
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c666c50bbf433230749914acdc941cb321713fbc;p=thirdparty%2Fapache%2Fhttpd.git

PR 62044: Force addition of generation number to shm filename on
all platforms. Keep persisted filename as-was.

[Reverted by r1822505]

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1822341 13f79535-47bb-0310-9956-ffa450edef68
---

diff --git a/CHANGES b/CHANGES
index a7656571db9..02fc6821101 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,9 @@
                                                          -*- coding: utf-8 -*-
 Changes with Apache 2.5.1
 
+  *) mod_slotmem_shm: Add generation number to shm filename to fix races
+     with graceful restarts. PR 62044.
+
   *) mpm_event: Let the listener thread do its maintenance job on resources
      shortage.  PR 61979.  [Yann Ylavic]
 
diff --git a/modules/slotmem/mod_slotmem_shm.c b/modules/slotmem/mod_slotmem_shm.c
index 04258def0ee..8e9b787cc30 100644
--- a/modules/slotmem/mod_slotmem_shm.c
+++ b/modules/slotmem/mod_slotmem_shm.c
@@ -71,31 +71,6 @@ static apr_pool_t *gpool = NULL;
 #define DEFAULT_SLOTMEM_SUFFIX ".shm"
 #define DEFAULT_SLOTMEM_PERSIST_SUFFIX ".persist"
 
-/* Unixes (and Netware) have the unlink() semantic, which allows to
- * apr_file_remove() a file still in use (opened elsewhere), the inode
- * remains until the last fd is closed, whereas any file created with
- * the same name/path will use a new inode.
- *
- * On windows and OS/2 ("\SHAREMEM\..." tree), apr_file_remove() marks
- * the files for deletion until the last HANDLE is closed, meanwhile the
- * same file/path can't be opened/recreated.
- * Thus on graceful restart (the only restart mode with mpm_winnt), the
- * old file may still exist until all the children stop, while we ought
- * to create a new one for our new clear SHM.  Therefore, we would only
- * be able to reuse (attach) the old SHM, preventing some changes to
- * the config file, like the number of balancers/members, since the
- * size checks (to fit the new config) would fail.  Let's avoid this by
- * including the generation number in the SHM filename (obviously not
- * the persisted name!)
- */
-#ifndef SLOTMEM_UNLINK_SEMANTIC
-#if defined(WIN32) || defined(OS2)
-#define SLOTMEM_UNLINK_SEMANTIC 0
-#else
-#define SLOTMEM_UNLINK_SEMANTIC 1
-#endif
-#endif
-
 /*
  * Persist the slotmem in a file
  * slotmem name and file name.
@@ -113,18 +88,11 @@ static int slotmem_filenames(apr_pool_t *pool,
 
     if (slotname && *slotname && strcasecmp(slotname, "none") != 0) {
         if (slotname[0] != '/') {
-#if !SLOTMEM_UNLINK_SEMANTIC
             /* Each generation needs its own file name. */
             int generation = 0;
             ap_mpm_query(AP_MPMQ_GENERATION, &generation);
             fname = apr_psprintf(pool, "%s%s_%x%s", DEFAULT_SLOTMEM_PREFIX,
                                  slotname, generation, DEFAULT_SLOTMEM_SUFFIX);
-#else
-            /* Reuse the same file name for each generation. */
-            fname = apr_pstrcat(pool, DEFAULT_SLOTMEM_PREFIX,
-                                slotname, DEFAULT_SLOTMEM_SUFFIX,
-                                NULL);
-#endif
             fname = ap_runtime_dir_relative(pool, fname);
         }
         else {
@@ -136,7 +104,6 @@ static int slotmem_filenames(apr_pool_t *pool,
 
         if (persistname) {
             /* Persisted file names are immutable... */
-#if !SLOTMEM_UNLINK_SEMANTIC
             if (slotname[0] != '/') {
                 pname = apr_pstrcat(pool, DEFAULT_SLOTMEM_PREFIX,
                                     slotname, DEFAULT_SLOTMEM_SUFFIX,
@@ -144,11 +111,11 @@ static int slotmem_filenames(apr_pool_t *pool,
                                     NULL);
                 pname = ap_runtime_dir_relative(pool, pname);
             }
-            else
-#endif
-            pname = apr_pstrcat(pool, fname,
-                                DEFAULT_SLOTMEM_PERSIST_SUFFIX,
-                                NULL);
+            else {
+                pname = apr_pstrcat(pool, slotname,
+                                    DEFAULT_SLOTMEM_PERSIST_SUFFIX,
+                                    NULL);
+            }
         }
     }