From: Ivan Maidanski <ivmai@mail.ru>
Date: Tue, 26 Sep 2017 21:56:14 +0000 (+0300)
Subject: Fix get_maps on proc maps file asynchronous growth
X-Git-Tag: v7.4.6~14
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=8a49b2ab3f51da89a85ea03e0f71fa1ad0940b71;p=gc

Fix get_maps on proc maps file asynchronous growth

Issue #179 (bdwgc).

Asynchronous growth of /proc/self/maps could be caused by some thread
which is not currently registered (e.g. stack allocation on thread
creation or a non-GC heap allocation from an unregistered thread).

* os_dep.c [NEED_PROC_MAPS] (GC_get_maps): Refine comment.
* os_dep.c [NEED_PROC_MAPS && THREADS] (GC_get_maps): Replace ABORT
with WARN call; refine printed message; add comment.
---

diff --git a/os_dep.c b/os_dep.c
index 68140027..5d88a499 100644
--- a/os_dep.c
+++ b/os_dep.c
@@ -178,9 +178,8 @@ GC_INNER char * GC_get_maps(void)
     /* stacks.  And there is no easy way to read the entire     */
     /* file atomically.  This is arguably a misfeature of the   */
     /* /proc/.../maps interface.                                */
-
-    /* Since we don't believe the file can grow                 */
-    /* asynchronously, it should suffice to first determine     */
+    /* Since we expect the file can grow asynchronously in rare */
+    /* cases, it should suffice to first determine              */
     /* the size (using lseek or read), and then to reread the   */
     /* file.  If the size is inconsistent we have to retry.     */
     /* This only matters with threads enabled, and if we use    */
@@ -230,10 +229,9 @@ GC_INNER char * GC_get_maps(void)
               return 0;
 #           ifdef THREADS
               if (maps_size > old_maps_size) {
-                ABORT_ARG2("Unexpected asynchronous /proc/self/maps growth "
-                           "(unregistered thread?)", " from %lu to %lu",
-                           (unsigned long)old_maps_size,
-                           (unsigned long)maps_size);
+                /* This might be caused by e.g. thread creation. */
+                WARN("Unexpected asynchronous /proc/self/maps growth"
+                     " (to %" WARN_PRIdPTR " bytes)\n", maps_size);
               }
 #           endif
         } while (maps_size >= maps_buf_sz || maps_size < old_maps_size);