* Second part of fix for PR 44402:

  - Fix the same race condition in event MPM.
  - Slightly optimize code in worker MPM by removing the need for an additional
    dereference operation.
  - Do some word smithing on the CHANGES entry.

PR: 44402
Submitted by: Basant Kumar Kukreja <basant.kukreja sun.com>
Reviewed by: rpluem

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@630348 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/CHANGES b/CHANGES
index c7fc3ab5879444405c3797711c9b22d28ecc97aa..b1b35805e293c2316ba0ec0633f135a2a927f931 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -2,8 +2,9 @@
 Changes with Apache 2.3.0
 [ When backported to 2.2.x, remove entry from this file ]
 
-  *) Worker MPM: fix race condition in recycling a pool
-     PR 44402 [Basant Kumar Kukreja <basant.kukreja sun.com>]
+  *) Worker / Event MPM: Fix race condition in pool recycling that leads to
+     segmentation faults under load.  PR 44402
+     [Basant Kumar Kukreja <basant.kukreja sun.com>]
 
   *) mod_include: Correctly handle SSI directives split over multiple filter
      passes.  PR 44447 [Harald Niesche <harald brokenerror.de>]

diff --git a/server/mpm/experimental/event/fdqueue.c b/server/mpm/experimental/event/fdqueue.c
index 8534a3e8de21ac8c17d46a069c7c4e13bfdb738c..925241909a66008cda27c8358d4c14e1d25af60e 100644 (file)
--- a/server/mpm/experimental/event/fdqueue.c
+++ b/server/mpm/experimental/event/fdqueue.c
@@ -201,10 +201,16 @@ void ap_push_pool(fd_queue_info_t * queue_info,
                                                           (*new_recycle));
         new_recycle->pool = pool_to_recycle;
         for (;;) {
-            new_recycle->next = queue_info->recycled_pools;
+            /*
+             * Save queue_info->recycled_pool in local variable next because
+             * new_recycle->next can be changed after apr_atomic_casptr
+             * function call.
+             */
+            struct recycled_pool *next = queue_info->recycled_pools;
+            new_recycle->next = next;
             if (apr_atomic_casptr
                 ((volatile void **) &(queue_info->recycled_pools),
-                 new_recycle, new_recycle->next) == new_recycle->next) {
+                 new_recycle, next) == next) {
                 break;
             }
         }

diff --git a/server/mpm/worker/fdqueue.c b/server/mpm/worker/fdqueue.c
index b88b8dacd83c716e8c84866fe2df1c330ff25e50..951fafacabf620f7414b4cfe53c90f6b45709f86 100644 (file)
--- a/server/mpm/worker/fdqueue.c
+++ b/server/mpm/worker/fdqueue.c
@@ -101,7 +101,7 @@ apr_status_t ap_queue_info_set_idle(fd_queue_info_t *queue_info,
             struct recycled_pool *next = queue_info->recycled_pools;
             new_recycle->next = next;
             if (apr_atomic_casptr((volatile void**)&(queue_info->recycled_pools),
-                                  new_recycle, new_recycle->next) == next) {
+                                  new_recycle, next) == next) {
                 break;
             }
         }