Implemented erlang:bump_reductions nif.

libs/estdlib/src/erlang.erl

@@ -131,7 +131,8 @@
     dist_ctrl_get_data/1,
     dist_ctrl_put_data/2,
     unique_integer/0,
-    unique_integer/1
+    unique_integer/1,
+    bump_reductions/1
 ]).
 
 -export_type([
@@ -272,7 +273,8 @@ send_after(Time, Dest, Msg) ->
     (Pid :: pid(), message_queue_len) -> {message_queue_len, non_neg_integer()};
     (Pid :: pid(), memory) -> {memory, non_neg_integer()};
     (Pid :: pid(), links) -> {links, [pid()]};
-    (Pid :: pid(), monitored_by) -> {monitored_by, [pid() | resource() | port()]}.
+    (Pid :: pid(), monitored_by) -> {monitored_by, [pid() | resource() | port()]};
+    (Pid :: pid(), reductions) -> {reductions, [pos_integer()]}.
 process_info(_Pid, _Key) ->
     erlang:nif_error(undefined).
 
@@ -1529,3 +1531,15 @@ unique_integer(_Options) ->
 -spec nif_error(Reason :: any()) -> no_return().
 nif_error(_Reason) ->
     erlang:nif_error(undefined).
+
+%%-----------------------------------------------------------------------------
+%% @param   Reductions  an integer representing a value of which the reduction counter
+%%          will be incremented by.
+%% @returns true
+%% @doc     Increments the reduction counter for the calling process, a context switch is
+%%          forced when the counter reaches the maximum number of reductions for a process.
+%% @end
+%%-----------------------------------------------------------------------------
+-spec bump_reductions(pos_integer()) -> true.
+bump_reductions(Reductions) when is_integer(Reductions), Reductions > 1 ->
+    erlang:nif_error(undefined).

src/libAtomVM/context.c

@@ -28,6 +28,7 @@
 #include "erl_nif.h"
 #include "erl_nif_priv.h"
 #include "globalcontext.h"
+#include "limits.h"
 #include "list.h"
 #include "mailbox.h"
 #include "smp.h"
@@ -89,6 +90,8 @@ Context *context_new(GlobalContext *glb)
 
     ctx->native_handler = NULL;
 
+    ctx->reductions = 0;
+
     ctx->saved_module = NULL;
     ctx->saved_ip = NULL;
     ctx->restore_trap_handler = NULL;
@@ -471,6 +474,7 @@ bool context_get_process_info(Context *ctx, term *out, size_t *term_size, term a
         case MESSAGE_QUEUE_LEN_ATOM:
         case REGISTERED_NAME_ATOM:
         case MEMORY_ATOM:
+        case REDUCTIONS_ATOM:
             ret_size = TUPLE_SIZE(2);
             break;
         case LINKS_ATOM: {
@@ -626,6 +630,23 @@ bool context_get_process_info(Context *ctx, term *out, size_t *term_size, term a
             break;
         }
 
+        case REDUCTIONS_ATOM: {
+            term_put_tuple_element(ret, 0, REDUCTIONS_ATOM);
+            if (UNLIKELY((uint64_t) LLONG_MAX < ctx->reductions)) {
+                *out = BADARG_ATOM;
+                return false;
+            }
+            int64_t reductions = (int64_t) ctx->reductions;
+            size_t reductions_size = term_boxed_integer_size(reductions);
+            if (UNLIKELY(memory_ensure_free_with_roots(ctx, reductions_size, 1, &ret, MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+                *out = OUT_OF_MEMORY_ATOM;
+                return false;
+            }
+            term reductions_term = term_make_maybe_boxed_int64(reductions, &ctx->heap);
+            term_put_tuple_element(ret, 1, reductions_term);
+            break;
+        }
+
         default:
             UNREACHABLE();
     }

src/libAtomVM/context.h

@@ -125,6 +125,8 @@ struct Context
     // Ports support
     native_handler_f native_handler;
 
+    uint64_t reductions;
+
     unsigned int leader : 1;
     unsigned int has_min_heap_size : 1;
     unsigned int has_max_heap_size : 1;

src/libAtomVM/defaultatoms.def

@@ -50,6 +50,7 @@ X(PORT_COUNT_ATOM, "\xA", "port_count")
 X(ATOM_COUNT_ATOM, "\xA", "atom_count")
 X(SYSTEM_ARCHITECTURE_ATOM, "\x13", "system_architecture")
 X(WORDSIZE_ATOM, "\x8", "wordsize")
+X(REDUCTIONS_ATOM, "\xA", "reductions")
 
 X(DECIMALS_ATOM, "\x8", "decimals")
 X(SCIENTIFIC_ATOM, "\xA", "scientific")

src/libAtomVM/nifs.c

@@ -202,6 +202,7 @@ static term nif_unicode_characters_to_list(Context *ctx, int argc, term argv[]);
 static term nif_unicode_characters_to_binary(Context *ctx, int argc, term argv[]);
 static term nif_erlang_lists_subtract(Context *ctx, int argc, term argv[]);
 static term nif_zlib_compress_1(Context *ctx, int argc, term argv[]);
+static term nif_erlang_bump_reductions_1(Context *ctx, int argc, term argv[]);
 
 #define DECLARE_MATH_NIF_FUN(moniker) \
     static term nif_math_##moniker(Context *ctx, int argc, term argv[]);
@@ -875,6 +876,11 @@ static const struct Nif zlib_compress_nif =
 };
 
 
+static const struct Nif erlang_bump_reductions_nif = {
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_erlang_bump_reductions_1
+};
+
 #define DEFINE_MATH_NIF(moniker)                    \
     static const struct Nif math_##moniker##_nif =  \
     {                                               \
@@ -5920,6 +5926,15 @@ static term nif_zlib_compress_1(Context *ctx, int argc, term argv[])
 }
 #endif
 
+static term nif_erlang_bump_reductions_1(Context *ctx, int argc, term argv[])
+{
+    UNUSED(argc);
+    VALIDATE_VALUE(argv[0], term_is_integer);
+    int64_t reductions_to_bump = term_to_int(argv[0]) - 1;
+    ctx->reductions += reductions_to_bump;
+    return TRUE_ATOM;
+}
+
 //
 // MAINTENANCE NOTE: Exception handling for fp operations using math
 // error handling is designed to be thread-safe, as errors are specified

src/libAtomVM/nifs.gperf

@@ -211,3 +211,4 @@ math:sqrt/1, &math_sqrt_nif
 math:tan/1, &math_tan_nif
 math:tanh/1, &math_tanh_nif
 zlib:compress/1, &zlib_compress_nif
+erlang:bump_reductions/1, &erlang_bump_reductions_nif

src/libAtomVM/opcodesswitch.h

@@ -1767,7 +1767,7 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
     Module *prev_mod;
     term *x_regs;
     const uint8_t *pc;
-    int remaining_reductions;
+    uint64_t max_reductions;
 
     Context *ctx = scheduler_run(glb);
 
@@ -1780,7 +1780,7 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
     code = mod->code->code;
     x_regs = ctx->x;
     pc = (ctx->saved_ip);
-    remaining_reductions = DEFAULT_REDUCTIONS_AMOUNT;
+    max_reductions = ctx->reductions + DEFAULT_REDUCTIONS_AMOUNT;
 
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wpedantic"
@@ -1864,8 +1864,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                 #ifdef IMPL_EXECUTE_LOOP
                     ctx->cp = module_address(mod->module_index, pc - code);
 
-                    remaining_reductions--;
-                    if (LIKELY(remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (LIKELY(ctx->reductions < max_reductions)) {
                         TRACE_CALL(ctx, mod, "call", label, arity);
                         JUMP_TO_ADDRESS(mod->labels[label]);
                     } else {
@@ -1895,8 +1895,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
 
                     DEBUG_DUMP_STACK(ctx);
 
-                    remaining_reductions--;
-                    if (LIKELY(remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (LIKELY(ctx->reductions < max_reductions)) {
                         TRACE_CALL(ctx, mod, "call_last", label, arity);
                         JUMP_TO_ADDRESS(mod->labels[label]);
                     } else {
@@ -1917,8 +1917,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                 USED_BY_TRACE(label);
 
                 #ifdef IMPL_EXECUTE_LOOP
-                    remaining_reductions--;
-                    if (LIKELY(remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (LIKELY(ctx->reductions < max_reductions)) {
                         TRACE_CALL(ctx, mod, "call_only", label, arity);
                         JUMP_TO_ADDRESS(mod->labels[label]);
                     } else {
@@ -1933,8 +1933,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                     // save pc in case of error
                     const uint8_t *orig_pc = pc - 1;
 
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, orig_pc);
                     }
                 #endif
@@ -2041,8 +2041,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                     // save pc in case of error
                     const uint8_t *orig_pc = pc - 1;
 
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, orig_pc);
                     }
                 #endif
@@ -3240,8 +3240,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                 USED_BY_TRACE(label);
 
                 #ifdef IMPL_EXECUTE_LOOP
-                    remaining_reductions--;
-                    if (LIKELY(remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (LIKELY(ctx->reductions < max_reductions)) {
                         JUMP_TO_ADDRESS(mod->labels[label]);
                     } else {
                         SCHEDULE_NEXT(mod, mod->labels[label]);
@@ -3477,8 +3477,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
 
             case OP_CALL_FUN: {
                 #ifdef IMPL_EXECUTE_LOOP
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, pc - 1);
                     }
                 #endif
@@ -3533,8 +3533,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
 
             case OP_CALL_EXT_ONLY: {
                 #ifdef IMPL_EXECUTE_LOOP
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, pc - 1);
                     }
                 #endif
@@ -5233,8 +5233,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
                     // save pc in case of error
                     const uint8_t *orig_pc = pc - 1;
 
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, orig_pc);
                     }
                 #endif
@@ -5286,8 +5286,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
 
             case OP_APPLY_LAST: {
                 #ifdef IMPL_EXECUTE_LOOP
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, pc - 1);
                     }
                 #endif
@@ -6793,8 +6793,8 @@ HOT_FUNC int scheduler_entry_point(GlobalContext *glb)
 
             case OP_CALL_FUN2: {
                 #ifdef IMPL_EXECUTE_LOOP
-                    remaining_reductions--;
-                    if (UNLIKELY(!remaining_reductions)) {
+                    ++ctx->reductions;
+                    if (UNLIKELY(ctx->reductions >= max_reductions)) {
                         SCHEDULE_NEXT(mod, pc - 1);
                     }
                 #endif

tests/erlang_tests/CMakeLists.txt

@@ -546,6 +546,8 @@ compile_erlang(test_raw_raise)
 compile_erlang(test_ets)
 compile_erlang(test_node)
 
+compile_erlang(test_bump_reductions)
+
 compile_erlang(test_op_bs_start_match)
 compile_assembler(test_op_bs_start_match_asm)
 compile_erlang(test_op_bs_create_bin)
@@ -1068,6 +1070,9 @@ add_custom_target(erlang_test_modules DEPENDS
     test_raw_raise.beam
 
     test_ets.beam
+
+    test_bump_reductions.beam
+
     test_node.beam
 
     test_op_bs_start_match.beam

tests/erlang_tests/test_bump_reductions.erl

@@ -0,0 +1,49 @@
+%
+% This file is part of AtomVM.
+%
+% Copyright 2025 Franciszek Kubis <[email protected]>
+%
+% Licensed under the Apache License, Version 2.0 (the "License");
+% you may not use this file except in compliance with the License.
+% You may obtain a copy of the License at
+%
+%    http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+% See the License for the specific language governing permissions and
+% limitations under the License.
+%
+% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
+%
+
+-module(test_bump_reductions).
+
+-export([start/0, process_test/0]).
+
+start() ->
+    {reductions, 1} = erlang:process_info(self(), reductions),
+    erlang:bump_reductions(500),
+    {reductions, 502} = erlang:process_info(self(), reductions),
+    Pid = erlang:spawn_opt(fun() -> process_test() end, [link]),
+    Pid ! {ready, self()},
+    receive
+        {r1, {reductions, Reductions}} ->
+            2 = Reductions
+    end,
+    receive
+        {r2, {reductions, Reductions2}} ->
+            1029 = Reductions2
+    end,
+    erlang:bump_reductions(2000),
+    {reductions, 2505} = erlang:process_info(self(), reductions),
+    0.
+
+process_test() ->
+    receive
+        {ready, Pid} ->
+            Pid ! {r1, erlang:process_info(self(), reductions)},
+            erlang:bump_reductions(1025),
+            Pid ! {r2, erlang:process_info(self(), reductions)}
+    end.

tests/test-structs.c

@@ -159,6 +159,8 @@ static const char *const bounded_free_atom = "\xC" "bounded_free";
 static const char *const minimum_atom = "\x7" "minimum";
 static const char *const fibonacci_atom = "\x9" "fibonacci";
 
+static const char *const reductions_atom = "\xA" "reductions";
+
 void test_valueshashtable()
 {
     struct ValuesHashTable *htable = valueshashtable_new();
@@ -429,6 +431,9 @@ atom_index_t insert_atoms_into_atom_table(struct AtomTable *table)
     assert(r == AtomTableEnsureAtomOk);
     r = atom_table_ensure_atom(table, (const uint8_t *) fibonacci_atom + 1, fibonacci_atom[0], AtomTableNoOpts, &global_atom_index);
 
+    assert(r == AtomTableEnsureAtomOk);
+    r = atom_table_ensure_atom(table, (const uint8_t *) reductions_atom + 1, reductions_atom[0], AtomTableNoOpts, &global_atom_index);
+
     return decimals_index;
 }
 

tests/test.c

@@ -598,6 +598,8 @@ struct Test tests[] = {
     TEST_CASE(test_ets),
     TEST_CASE(test_node),
 
+    TEST_CASE(test_bump_reductions),
+
     // TEST CRASHES HERE: TEST_CASE(memlimit),
 
     { NULL, 0, false, false }