[SVN-4157] BDB incompatible with event MPM

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: trunk
• Component/s: libsvn_fs_base
• Assignee: Unassigned
• Reporter: Philip Martin
• Created: 05/Apr/12 07:20
• Updated: 27/Oct/18 16:28
• Resolved: 17/Feb/15 15:39

Description

See this thread:

http://mail-archives.apache.org/mod_mbox/subversion-dev/201204.mbox/[e-mail]%3E
http://svn.haxx.se/dev/archive-2012-04/0017.shtml

The event MPM is the default MPM for Apache 2.4 having been experimental in 2.2. The event MPM is incompatible with Subversion's BDB backend.

The problem is Subversion's per-thread BDB error handling structures. Subversion assumes that the same thread will allocate and release these structures, i.e. that the access will be by a single thread. The event MPM switches threads
although the access is probably "one thread at a time".

This patch causes assertion failures with the event MPM:

Index: subversion/libsvn_fs_base/bdb/env.c
===================================================================
--- subversion/libsvn_fs_base/bdb/env.c	(revision 1309593)
+++ subversion/libsvn_fs_base/bdb/env.c	(working copy)
@@ -186,6 +186,7 @@ get_error_info(const bdb_env_t *bdb)
   if (!priv)
     {
       priv = calloc(1, sizeof(bdb_error_info_t));
+      ((struct bdb_error_info_t *)priv)->id = pthread_self();
       apr_threadkey_private_set(priv, bdb->error_info);
     }
   return priv;
@@ -524,6 +525,7 @@ svn_fs_bdb__close(bdb_env_baton_t *bdb_baton)
 
   SVN_ERR_ASSERT(bdb_baton->env == bdb_baton->bdb->env);
   SVN_ERR_ASSERT(bdb_baton->error_info->refcount > 0);
+  SVN_ERR_ASSERT(pthread_equal(bdb_baton->error_info->id, pthread_self()));
 
   /* Neutralize bdb_baton's pool cleanup to prevent double-close. See
      cleanup_env_baton(). */
Index: subversion/libsvn_fs_base/bdb/env.h
===================================================================
--- subversion/libsvn_fs_base/bdb/env.h	(revision 1309593)
+++ subversion/libsvn_fs_base/bdb/env.h	(working copy)
@@ -71,6 +71,8 @@ typedef struct bdb_error_info_t
      instances that refer to this object. */
   unsigned refcount;
 
+  pthread_t id;
+
 } bdb_error_info_t;

Issue Links

• is duplicated by: SVN-4147 bdb tests hang against httpd-2.4