erts: Fix confusion of callbacks destroying_mbc() vs remove_mbc()

Problem #1 Goodfit was crippled by the fact that destroying_mbc()
was called _before_ the carriers was unlinked from mbc_list.

Problem #2 destroying_mbc() was called for carriers that later could be
resurrected from dc_list without a matching call to creating_mbc().
This was mostly a practical problem for the new test case
alloc_SUITE:migration that use the callbacks to create/destroy a mutex.

Solution:
destroying_mbc() is now only called just before a carrier is
destroyed (deallocated or put in mseg cache).

remove_mbc() is called both (like before) when inserted into cpool
but now also when last block is freed and mbc is scheduled for
destruction but may later be resurrected from dc_list.

1 files changed, 1 insertions, 1 deletions

diff --git a/erts/emulator/beam/erl_alloc_util.h b/erts/emulator/beam/erl_alloc_util.h
index df1f0aa65a..f4a2ae7ff3 100644
--- a/erts/emulator/beam/erl_alloc_util.h
+++ b/erts/emulator/beam/erl_alloc_util.h
@@ -277,7 +277,7 @@ typedef struct ErtsDoubleLink_t_ {
 typedef struct {
     erts_atomic_t next;
     erts_atomic_t prev;
-    Allctr_t *orig_allctr;
+    Allctr_t *orig_allctr;      /* read-only while carrier is alive */
     ErtsThrPrgrVal thr_prgr;
     erts_atomic_t max_size;
     UWord abandon_limit;