From af5169d85fcd545e3c857a219db081a62f33404d Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Thu, 12 Jan 2017 13:58:26 +0100 Subject: erts: Fix race bug between export fun creation and code loading Symptom: SEGV crash on ARM in delete_code() -> export_list(). Could probably happen on other machines as well. Problem: Staging export table was iterated in an unsafe way while an entry was added for a new export fun. Solution: Correct write order and some memory barriers. --- erts/emulator/beam/index.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'erts/emulator/beam/index.h') diff --git a/erts/emulator/beam/index.h b/erts/emulator/beam/index.h index 0a109d8699..532dec0168 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 -- cgit v1.2.3