Merge branch 'sverker/24/erts/fix-factory-undo/OTP-18027' into maint

This merge commit contains a partial revert of
a96f282359cd5f9f035029e99b0a5db360651a94
as we merge an alternative fix to the same problem.

1 files changed, 20 insertions, 19 deletions

diff --git a/erts/emulator/beam/erl_message.c b/erts/emulator/beam/erl_message.c
index 05d803168a..d183427165 100644
--- a/erts/emulator/beam/erl_message.c
+++ b/erts/emulator/beam/erl_message.c
@@ -1496,32 +1496,33 @@ void erts_factory_undo(ErtsHeapFactory* factory)
         }
 
         if (factory->mode == FACTORY_HALLOC) {
-            /* Reset all the heap fragments we've added. Note that we CANNOT
-             * free them, as someone else might have grabbed a reference to
-             * them (e.g. the callers of `erts_gc_after_bif_call_lhf`).
-             *
-             * The GC will get rid of these later on. Note that we leave
-             * `p->mbuf_sz` untouched to keep the memory pressure of these
-             * fragments. */
-            for (bp = (factory->p)->mbuf;
-                 bp != factory->heap_frags_saved;
-                 bp = bp->next) {
-                ASSERT(bp->off_heap.first == NULL);
-                bp->used_size = 0;
+            /* Free heap frags
+             */
+            bp = factory->p->mbuf;
+            if (bp != factory->heap_frags_saved) {
+                do {
+                    ErlHeapFragment *next_bp = bp->next;
+                    ASSERT(bp->off_heap.first == NULL);
+                    ERTS_HEAP_FREE(ERTS_ALC_T_HEAP_FRAG, (void *) bp,
+                                   ERTS_HEAP_FRAG_SIZE(bp->alloc_size));
+                    bp = next_bp;
+                } while (bp != factory->heap_frags_saved);
+
+                factory->p->mbuf = bp;
             }
 
-            /* Roll back the size of the latest fragment not allocated by us,
-             * as we may have used a part of it. */
-            if (bp != NULL) {
-                ASSERT(bp == factory->heap_frags_saved);
-                bp->used_size = factory->heap_frags_saved_used;
-            }
+            /* Rollback heap top
+	     */
 
-            /* Roll back heap top */
             ASSERT(HEAP_START(factory->p) <= factory->original_htop);
             ASSERT(factory->original_htop <= HEAP_LIMIT(factory->p));
             HEAP_TOP(factory->p) = factory->original_htop;
 
+	    /* Fix last heap frag */
+            if (factory->heap_frags_saved) {
+                ASSERT(factory->heap_frags_saved == factory->p->mbuf);
+                factory->heap_frags_saved->used_size = factory->heap_frags_saved_used;
+            }
             if (factory->message) {
                 ASSERT(factory->message->data.attached != ERTS_MSG_COMBINED_HFRAG);
                 ASSERT(!factory->message->data.heap_frag);