Merge branch 'maint'

7 files changed, 58 insertions, 14 deletions

diff --git a/erts/doc/src/notes.xml b/erts/doc/src/notes.xml
index 11777f0014..812538729d 100644
--- a/erts/doc/src/notes.xml
+++ b/erts/doc/src/notes.xml
@@ -32,6 +32,26 @@
   <p>This document describes the changes made to the ERTS application.</p>
 
 
+<section><title>Erts 8.2.1</title>
+
+    <section><title>Fixed Bugs and Malfunctions</title>
+      <list>
+        <item>
+          <p>
+	    Fix a quite rare bug causing VM crash during code loading
+	    and the use of export funs (fun M:F/A) of not yet loaded
+	    modules. Requires a very specfic timing of concurrent
+	    scheduler threads. Has been seen on ARM but can probably
+	    also occure on other architectures. Bug has existed since
+	    OTP R16.</p>
+          <p>
+	    Own Id: OTP-14144 Aux Id: seq13242 </p>
+        </item>
+      </list>
+    </section>
+
+</section>
+
 <section><title>Erts 8.2</title>
 
     <section><title>Fixed Bugs and Malfunctions</title>
diff --git a/erts/emulator/beam/beam_bif_load.c b/erts/emulator/beam/beam_bif_load.c
index 09331eb8ad..2d1aa13004 100644
--- a/erts/emulator/beam/beam_bif_load.c
+++ b/erts/emulator/beam/beam_bif_load.c
@@ -806,7 +806,7 @@ BIF_RETTYPE finish_after_on_load_2(BIF_ALIST_2)
     }
 
     if (BIF_ARG_2 == am_true) {
-	int i;
+	int i, num_exps;
 
 	/*
 	 * Make the code with the on_load function current.
@@ -822,7 +822,8 @@ BIF_RETTYPE finish_after_on_load_2(BIF_ALIST_2)
 	/*
 	 * The on_load function succeded. Fix up export entries.
 	 */
-	for (i = 0; i < export_list_size(code_ix); i++) {
+	num_exps = export_list_size(code_ix);
+	for (i = 0; i < num_exps; i++) {
 	    Export *ep = export_list(i,code_ix);
 	    if (ep == NULL || ep->info.mfa.module != BIF_ARG_1) {
 		continue;
@@ -845,14 +846,15 @@ BIF_RETTYPE finish_after_on_load_2(BIF_ALIST_2)
         hipe_redirect_to_module(modp);
       #endif
     } else if (BIF_ARG_2 == am_false) {
-	int i;
+	int i, num_exps;
 
 	/*
 	 * The on_load function failed. Remove references to the
 	 * code that is about to be purged from the export entries.
 	 */
 
-	for (i = 0; i < export_list_size(code_ix); i++) {
+	num_exps = export_list_size(code_ix);
+	for (i = 0; i < num_exps; i++) {
 	    Export *ep = export_list(i,code_ix);
 	    if (ep == NULL || ep->info.mfa.module != BIF_ARG_1) {
 		continue;
@@ -1783,9 +1785,9 @@ delete_code(Module* modp)
 {
     ErtsCodeIndex code_ix = erts_staging_code_ix();
     Eterm module = make_atom(modp->module);
-    int i;
+    int i, num_exps = export_list_size(code_ix);
 
-    for (i = 0; i < export_list_size(code_ix); i++) {
+    for (i = 0; i < num_exps; i++) {
 	Export *ep = export_list(i, code_ix);
         if (ep != NULL && (ep->info.mfa.module == module)) {
 	    if (ep->addressv[code_ix] == ep->beam) {
diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index 8f1faa6719..309465bcd3 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -800,14 +800,14 @@ erts_finish_loading(Binary* magic, Process* c_p,
     } else {
 	ErtsCodeIndex code_ix = erts_staging_code_ix();
 	Eterm module = stp->module;
-	int i;
+	int i, num_exps;
 
 	/*
 	 * There is an -on_load() function. We will keep the current
 	 * code, but we must turn off any tracing.
 	 */
-
-	for (i = 0; i < export_list_size(code_ix); i++) {
+        num_exps = export_list_size(code_ix);
+	for (i = 0; i < num_exps; i++) {
 	    Export *ep = export_list(i, code_ix);
 	    if (ep == NULL || ep->info.mfa.module != module) {
 		continue;
@@ -5724,12 +5724,13 @@ exported_from_module(Process* p, /* Process whose heap to use. */
                      ErtsCodeIndex code_ix,
 		     Eterm mod) /* Tagged atom for module. */
 {
-    int i;
+    int i, num_exps;
     Eterm* hp = NULL;
     Eterm* hend = NULL;
     Eterm result = NIL;
 
-    for (i = 0; i < export_list_size(code_ix); i++) {
+    num_exps = export_list_size(code_ix);
+    for (i = 0; i < num_exps; i++) {
 	Export* ep = export_list(i,code_ix);
 	
 	if (ep->info.mfa.module == mod) {
diff --git a/erts/emulator/beam/export.c b/erts/emulator/beam/export.c
index f397ab6b00..33ed6d7ec1 100644
--- a/erts/emulator/beam/export.c
+++ b/erts/emulator/beam/export.c
@@ -356,7 +356,7 @@ Export *export_list(int i, ErtsCodeIndex code_ix)
 
 int export_list_size(ErtsCodeIndex code_ix)
 {
-    return export_tables[code_ix].entries;
+    return erts_index_num_entries(&export_tables[code_ix]);
 }
 
 int export_table_sz(void)
diff --git a/erts/emulator/beam/index.c b/erts/emulator/beam/index.c
index c86a2122f6..cd834e2c12 100644
--- a/erts/emulator/beam/index.c
+++ b/erts/emulator/beam/index.c
@@ -91,9 +91,16 @@ index_put_entry(IndexTable* t, void* tmpl)
 	t->seg_table[ix>>INDEX_PAGE_SHIFT] = erts_alloc(t->type, sz);
 	t->size += INDEX_PAGE_SIZE;
     }
-    t->entries++;
     p->index = ix;
     t->seg_table[ix>>INDEX_PAGE_SHIFT][ix&INDEX_PAGE_MASK] = p;
+
+    /*
+     * Do a write barrier here to allow readers to do lock free iteration.
+     * erts_index_num_entries() does matching read barrier.
+     */
+    ERTS_SMP_WRITE_MEMORY_BARRIER;
+    t->entries++;
+
     return p;
 }
 
diff --git a/erts/emulator/beam/index.h b/erts/emulator/beam/index.h
index b2e3c0eab5..10f5d1eb39 100644
--- a/erts/emulator/beam/index.h
+++ b/erts/emulator/beam/index.h
@@ -65,6 +65,7 @@ void index_erase_latest_from(IndexTable*, Uint ix);
 
 ERTS_GLB_INLINE int index_put(IndexTable*, void*);
 ERTS_GLB_INLINE IndexSlot* erts_index_lookup(IndexTable*, Uint);
+ERTS_GLB_INLINE int erts_index_num_entries(IndexTable* t);
 
 #if ERTS_GLB_INLINE_INCL_FUNC_DEF
 
@@ -78,6 +79,19 @@ erts_index_lookup(IndexTable* t, Uint ix)
 {
     return t->seg_table[ix>>INDEX_PAGE_SHIFT][ix&INDEX_PAGE_MASK];
 }
+
+ERTS_GLB_INLINE int erts_index_num_entries(IndexTable* t)
+{
+    int ret = t->entries;
+    /*
+     * Do a read barrier here to allow lock free iteration
+     * on tables where entries are never erased.
+     * index_put_entry() does matching write barrier.
+     */
+    ERTS_SMP_READ_MEMORY_BARRIER;
+    return ret;
+}
+
 #endif
 
 #endif
diff --git a/erts/vsn.mk b/erts/vsn.mk
index af0be85062..028b114068 100644
--- a/erts/vsn.mk
+++ b/erts/vsn.mk
@@ -18,7 +18,7 @@
 # %CopyrightEnd%
 # 
 
-VSN = 8.2
+VSN = 8.2.1
 
 # Port number 4365 in 4.2
 # Port number 4366 in 4.3