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Avoid enqueueing the same ISeq twice

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by a race condition by multiple Ractors.

Atmically incrementing body->total_calls may have its own cost, so for
now we intentionally leave the unreliable total_calls. So we allow an
ISeq to be never pushed when you use multiple Ractors. However, if you
enqueue a single ccan node twice, get_from_list loops infinitely. Thus
this patch takes care of such a situation.
This commit is contained in:
Takashi Kokubun 2021-06-10 00:32:15 -07:00
parent 791d7d4947
commit c5e8a49bde
No known key found for this signature in database
GPG key ID: 6FFC433B12EE23DD
4 changed files with 23 additions and 12 deletions
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1
common.mk
View file

@ -8608,6 +8608,7 @@ mjit.$(OBJEXT): {$(VPATH)}util.h
mjit.$(OBJEXT): {$(VPATH)}vm_callinfo.h
mjit.$(OBJEXT): {$(VPATH)}vm_core.h
mjit.$(OBJEXT): {$(VPATH)}vm_opts.h
mjit.$(OBJEXT): {$(VPATH)}vm_sync.h
mjit_build_dir.$(OBJEXT): {$(VPATH)}config.h
mjit_build_dir.$(OBJEXT): {$(VPATH)}internal/compiler_is.h
mjit_build_dir.$(OBJEXT): {$(VPATH)}internal/compiler_is/apple.h

30
mjit.c
View file

@ -23,6 +23,7 @@
#include "internal/file.h"
#include "internal/hash.h"
#include "internal/warnings.h"
#include "vm_sync.h"
#include "mjit_worker.c"
@ -253,18 +254,28 @@ mjit_target_iseq_p(struct rb_iseq_constant_body *body)
&& !body->builtin_inline_p;
}
// This is called from an MJIT worker when worker_p is true.
// If recompile_p is true, the call is initiated by mjit_recompile.
// This assumes the caller holds CRITICAL_SECTION when recompile_p is true.
static void
mjit_add_iseq_to_process(const rb_iseq_t *iseq, const struct rb_mjit_compile_info *compile_info, bool worker_p)
mjit_add_iseq_to_process(const rb_iseq_t *iseq, const struct rb_mjit_compile_info *compile_info, bool recompile_p)
{
if (!mjit_enabled || pch_status == PCH_FAILED)
return;
if (!mjit_target_iseq_p(iseq->body)) {
iseq->body->jit_func = (mjit_func_t)NOT_COMPILED_JIT_ISEQ_FUNC; // skip mjit_wait
return;
}
if (!recompile_p) {
CRITICAL_SECTION_START(3, "in add_iseq_to_process");
// This prevents multiple Ractors from enqueueing the same ISeq twice.
if (rb_multi_ractor_p() && iseq->body->jit_func != NOT_ADDED_JIT_ISEQ_FUNC) {
CRITICAL_SECTION_FINISH(3, "in add_iseq_to_process");
return;
}
}
RB_DEBUG_COUNTER_INC(mjit_add_iseq_to_process);
iseq->body->jit_func = (mjit_func_t)NOT_READY_JIT_ISEQ_FUNC;
create_unit(iseq);
@ -273,15 +284,12 @@ mjit_add_iseq_to_process(const rb_iseq_t *iseq, const struct rb_mjit_compile_inf
return;
if (compile_info != NULL)
iseq->body->jit_unit->compile_info = *compile_info;
if (!worker_p) {
CRITICAL_SECTION_START(3, "in add_iseq_to_process");
}
add_to_list(iseq->body->jit_unit, &unit_queue);
if (active_units.length >= mjit_opts.max_cache_size) {
unload_requests++;
}
if (!worker_p) {
if (!recompile_p) {
verbose(3, "Sending wakeup signal to workers in mjit_add_iseq_to_process");
rb_native_cond_broadcast(&mjit_worker_wakeup);
CRITICAL_SECTION_FINISH(3, "in add_iseq_to_process");
@ -356,9 +364,11 @@ mjit_recompile(const rb_iseq_t *iseq)
assert(iseq->body->jit_unit != NULL);
if (UNLIKELY(mjit_opts.wait)) {
CRITICAL_SECTION_START(3, "in rb_mjit_recompile_iseq");
remove_from_list(iseq->body->jit_unit, &active_units);
add_to_list(iseq->body->jit_unit, &stale_units);
mjit_add_iseq_to_process(iseq, &iseq->body->jit_unit->compile_info, false);
mjit_add_iseq_to_process(iseq, &iseq->body->jit_unit->compile_info, true);
CRITICAL_SECTION_FINISH(3, "in rb_mjit_recompile_iseq");
mjit_wait(iseq->body);
}
else {
@ -367,7 +377,7 @@ mjit_recompile(const rb_iseq_t *iseq)
// It's good to avoid a race condition between mjit_add_iseq_to_process and mjit_compile around jit_unit as well.
CRITICAL_SECTION_START(3, "in rb_mjit_recompile_iseq");
iseq->body->jit_unit->stale_p = true;
iseq->body->jit_func = (mjit_func_t)NOT_ADDED_JIT_ISEQ_FUNC;
iseq->body->jit_func = (mjit_func_t)NOT_READY_JIT_ISEQ_FUNC;
pending_stale_p = true;
CRITICAL_SECTION_FINISH(3, "in rb_mjit_recompile_iseq");
}

2
mjit.h
View file

@ -20,7 +20,7 @@
// Special address values of a function generated from the
// corresponding iseq by MJIT:
enum rb_mjit_iseq_func {
// ISEQ was not queued yet for the machine code generation
// ISEQ has never been enqueued to unit_queue yet
NOT_ADDED_JIT_ISEQ_FUNC = 0,
// ISEQ is already queued for the machine code generation but the
// code is not ready yet for the execution

2
mjit_worker.c
View file

@ -1106,7 +1106,7 @@ load_func_from_so(const char *so_file, const char *funcname, struct rb_mjit_unit
handle = dlopen(so_file, RTLD_NOW);
if (handle == NULL) {
mjit_warning("failure in loading code from '%s': %s", so_file, dlerror());
return (void *)NOT_ADDED_JIT_ISEQ_FUNC;
return (void *)NOT_COMPILED_JIT_ISEQ_FUNC;
}
func = dlsym(handle, funcname);