erts: Fix race in fun loading

Because funs are tied to their canonical module rather than a
specific instance of a module, they are "moved over" to the newest
instance whenever we reload _the exact same module_ over itself.

This quirk, together with how fun entries are updated when a module
is loaded, caused a small window where it was possible for a holder
of an "old" fun to call the new instance before it was fully loaded.

This commit fixes that by versioning funs in roughly the same way
we do exports. It also fixes a related bug where fun purging could
be messed up if a new module instance was loaded in the middle of
purging, solving the issue by disallowing code loading while
purging a module with funs.

1 files changed, 3 insertions, 3 deletions

diff --git a/erts/emulator/beam/beam_bp.c b/erts/emulator/beam/beam_bp.c
index 023e67a96a..82bb8c5eb8 100644
--- a/erts/emulator/beam/beam_bp.c
+++ b/erts/emulator/beam/beam_bp.c
@@ -289,7 +289,7 @@ erts_consolidate_bp_data(BpFunctions* f, int local)
     Uint i;
     Uint n = f->matched;
 
-    ERTS_LC_ASSERT(erts_has_code_write_permission());
+    ERTS_LC_ASSERT(erts_has_code_mod_permission());
 
     for (i = 0; i < n; i++) {
         consolidate_bp_data(fs[i].mod, fs[i].ci_rw, local);
@@ -1397,7 +1397,7 @@ set_function_break(ErtsCodeInfo *ci, Binary *match_spec, Uint break_flags,
     Uint common;
     ErtsBpIndex ix = erts_staging_bp_ix();
 
-    ERTS_LC_ASSERT(erts_has_code_write_permission());
+    ERTS_LC_ASSERT(erts_has_code_mod_permission());
     g = ci->u.gen_bp;
     if (g == 0) {
 	int i;
@@ -1530,7 +1530,7 @@ clear_function_break(const ErtsCodeInfo *ci, Uint break_flags)
     Uint common;
     ErtsBpIndex ix = erts_staging_bp_ix();
 
-    ERTS_LC_ASSERT(erts_has_code_write_permission());
+    ERTS_LC_ASSERT(erts_has_code_mod_permission());
 
     if ((g = ci->u.gen_bp) == NULL) {
 	return 1;