From b628ebe21a7b449eea27ada811dfbb007afe6d0b Mon Sep 17 00:00:00 2001
From: Patrik Nyblom <pan@erlang.org>
Date: Wed, 21 Nov 2012 17:58:19 +0100
Subject: Teach erts_bs_append not to dump core

When erts_bs_append() calls the garbage collector, it has set
the PB_ACTIVE_WRITER flag in the ProcBin for the binary object
is about to be appended to. Therefore, it is expected that the
garbage collector should neither move nor shrink the binary
object.

But if the garbage collector does a minor collection (thereby
clearing the PB_ACTIVE_WRITER flag in the ProcBin) and there is
still not enough heap space, there will be a second major
garbage collection. During the major collection (since the
the PB_ACTIVE_WRITER flag was cleared), the binary object may
be shrunk or moved (depending on sizes and how many other
writable binaries there are in the process).

Avoid the problem by clearing the PB_ACTIVE_WRITER flags in
a separate pass after the garbage collection(s).

Thanks to Denis Titoruk for helping us find this bug.
---
 erts/emulator/beam/erl_gc.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

(limited to 'erts')

diff --git a/erts/emulator/beam/erl_gc.c b/erts/emulator/beam/erl_gc.c
index 52a6e52e6c..e2689f58c3 100644
--- a/erts/emulator/beam/erl_gc.c
+++ b/erts/emulator/beam/erl_gc.c
@@ -336,6 +336,19 @@ erts_gc_after_bif_call(Process* p, Eterm result, Eterm* regs, Uint arity)
     return result;
 }
 
+static ERTS_INLINE void reset_active_writer(Process *p)
+{
+    struct erl_off_heap_header* ptr;
+    ptr = MSO(p).first;
+    while (ptr) {
+	if (ptr->thing_word == HEADER_PROC_BIN) {	
+	    ProcBin *pbp = (ProcBin*) ptr;
+	    pbp->flags &= ~PB_ACTIVE_WRITER;
+	}
+	ptr = ptr->next;
+    }
+}
+
 /*
  * Garbage collect a process.
  *
@@ -395,6 +408,7 @@ erts_garbage_collect(Process* p, int need, Eterm* objv, int nobj)
 	    DTRACE2(gc_minor_end, pidbuf, reclaimed_now);
 	}
     }
+    reset_active_writer(p);
 
     /*
      * Finish.
@@ -2181,7 +2195,6 @@ link_live_proc_bin(struct shrink_cand_data *shrink,
 
 
 	if (pbp->flags & PB_ACTIVE_WRITER) {
-	    pbp->flags &= ~PB_ACTIVE_WRITER;
 	    shrink->no_of_active++;
 	}
 	else { /* inactive */
-- 
cgit v1.2.3


From 9966b521944520d388eeb36eea70fb60aeb692ab Mon Sep 17 00:00:00 2001
From: Patrik Nyblom <pan@erlang.org>
Date: Thu, 22 Nov 2012 16:35:40 +0100
Subject: Correct doc of process_info(Pid,links)

---
 erts/doc/src/erlang.xml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'erts')

diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 248b755969..d85dff2c0c 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -3998,10 +3998,10 @@ os_prompt% </pre>
               the initial function call with which the process was
               spawned.</p>
           </item>
-          <tag><c>{links, Pids}</c></tag>
+          <tag><c>{links, PidsAndPorts}</c></tag>
           <item>
-            <p><c>Pids</c> is a list of pids, with processes to
-              which the process has a link.</p>
+            <p><c>PidsAndPorts</c> is a list of pids and port identifiers, with 
+	    processes or ports to which the process has a link.</p>
           </item>
           <tag><c>{last_calls, false|Calls}</c></tag>
           <item>
-- 
cgit v1.2.3