From a1cde0f881ee4865d38e2e6e88cc71dcd362fdd2 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas.larsson@erlang-solutions.com>
Date: Thu, 17 Mar 2016 11:15:54 +0100
Subject: erts: Deallocate heap fragments from trace nif calls
Any heap fragment created during a nif call to a tracer nif
should be free'd immediately in order for the GC not to treat
it as live data.
---
erts/emulator/beam/beam_emu.c | 2 +-
erts/emulator/beam/erl_nif.c | 31 ++++++++++++++++++++++++++++---
2 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 7cb259cb8a..254bfe4ba0 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -3346,7 +3346,7 @@ do { \
OpCase(normal_exit): {
SWAPOUT;
c_p->freason = EXC_NORMAL;
- c_p->arity = 0; /* In case this process will ever be garbed again. */
+ c_p->arity = 0; /* In case this process will never be garbed again. */
ERTS_SMP_UNREQ_PROC_MAIN_LOCK(c_p);
erts_do_exit_process(c_p, am_normal);
ERTS_SMP_REQ_PROC_MAIN_LOCK(c_p);
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 7ab5421c91..73c0eb8eba 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -92,11 +92,12 @@ static ERTS_INLINE Eterm* alloc_heap(ErlNifEnv* env, unsigned need)
}
static Eterm* alloc_heap_heavy(ErlNifEnv* env, unsigned need, Eterm* hp)
-{
+{
env->hp = hp;
- if (env->heap_frag == NULL) {
+ if (env->heap_frag == NULL) {
ASSERT(HEAP_LIMIT(env->proc) == env->hp_end);
- HEAP_TOP(env->proc) = env->hp;
+ ASSERT(env->hp + need > env->hp_end);
+ HEAP_TOP(env->proc) = env->hp;
}
else {
env->heap_frag->used_size = hp - env->heap_frag->mem;
@@ -3165,13 +3166,37 @@ Eterm erts_nif_call_function(Process *p, Process *tracee,
|| erts_smp_thr_progress_is_blocking());
#endif
if (p) {
+ /* This is almost a normal nif call like in beam_emu,
+ except that any heap fragment created in the nif will be
+ discarded without checking if anything in it is live.
+ This is because we cannot do a GC here as we don't know
+ the number of live registers that have to be preserved.
+ This means that any heap part of the returned term may
+ not be used outside this function. */
struct enif_environment_t env;
+ ErlHeapFragment *orig_hf = MBUF(p);
+ ErlOffHeap orig_oh = MSO(p);
ASSERT(is_internal_pid(p->common.id));
+ MBUF(p) = NULL;
+ clear_offheap(&MSO(p));
+
erts_pre_nif(&env, p, mod, tracee);
nif_result = (*fun->fptr)(&env, argc, argv);
if (env.exception_thrown)
nif_result = THE_NON_VALUE;
erts_post_nif(&env);
+
+ /* Free any offheap and heap fragments created in nif */
+ if (MSO(p).first) {
+ erts_cleanup_offheap(&MSO(p));
+ clear_offheap(&MSO(p));
+ }
+ if (MBUF(p))
+ free_message_buffer(MBUF(p));
+
+ /* restore original heap fragment list */
+ MBUF(p) = orig_hf;
+ MSO(p) = orig_oh;
} else {
/* Nif call was done without a process context,
so we create a phony one. */
--
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