k0kubun	2019-03-18 03:07:06 +0900 (Mon, 18 Mar 2019)

  New Revision: 67287

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=67287

  Log:
    Eliminate mjit_copy_job_t reference from mjit_worker
    
    and make `copy_cache_from_main_thread` easier to use.
    
    For implementing inlining later, I'll use `copy_cache_from_main_thread`
    inside `mjit_compile`.

  Modified files:
    trunk/mjit_worker.c
Index: mjit_worker.c
===================================================================
--- mjit_worker.c	(revision 67286)
+++ mjit_worker.c	(revision 67287)
@@ -1141,33 +1141,66 @@ static void mjit_copy_job_handler(void * https://github.com/ruby/ruby/blob/trunk/mjit_worker.c#L1141
 /* vm_trace.c */
 int rb_workqueue_register(unsigned flags, rb_postponed_job_func_t , void *);
 
-/* We're lazily copying cache values from main thread because these cache values
-   could be different between ones on enqueue timing and ones on dequeue timing.
-   Return true if copy succeeds. */
+// Copy inline cache values of `iseq` to `*cc_entries` and `*is_entries`.
+// Return true if copy succeeds or is not needed.
+//
+// We're lazily copying cache values from main thread because these cache values
+// could be different between ones on enqueue timing and ones on dequeue timing.
 static bool
-copy_cache_from_main_thread(mjit_copy_job_t *job)
+copy_cache_from_main_thread(const rb_iseq_t *iseq, struct rb_call_cache **cc_entries, union iseq_inline_storage_entry **is_entries)
 {
+    mjit_copy_job_t *job = &mjit_copy_job; // just a short hand
+
+    CRITICAL_SECTION_START(3, "in copy_cache_from_main_thread");
+    job->finish_p = true; // disable dispatching this job in mjit_copy_job_handler while it's being modified
+    CRITICAL_SECTION_FINISH(3, "in copy_cache_from_main_thread");
+
+    const struct rb_iseq_constant_body *body = iseq->body;
+    job->cc_entries = NULL;
+    if (body->ci_size > 0 || body->ci_kw_size > 0)
+        job->cc_entries = alloca(sizeof(struct rb_call_cache) * (body->ci_size + body->ci_kw_size));
+    job->is_entries = NULL;
+    if (body->is_size > 0)
+        job->is_entries = alloca(sizeof(union iseq_inline_storage_entry) * body->is_size);
+
+    // If ISeq has no inline cache, there's no need to run a copy job.
+    if (job->cc_entries == NULL && job->is_entries == NULL) {
+        *cc_entries = job->cc_entries;
+        *is_entries = job->is_entries;
+        return true;
+    }
+
     CRITICAL_SECTION_START(3, "in copy_cache_from_main_thread");
+    job->iseq = iseq; // Prevernt GC of this ISeq from here
     job->finish_p = false; // allow dispatching this job in mjit_copy_job_handler
     CRITICAL_SECTION_FINISH(3, "in copy_cache_from_main_thread");
 
     if (UNLIKELY(mjit_opts.wait)) {
         mjit_copy_job_handler((void *)job);
-        return job->finish_p;
+    } else if (rb_workqueue_register(0, mjit_copy_job_handler, (void *)job)) {
+        CRITICAL_SECTION_START(3, "in MJIT copy job wait");
+        // checking `stop_worker_p` too because `RUBY_VM_CHECK_INTS(ec)` may not
+        // lush mjit_copy_job_handler when EC_EXEC_TAG() is not TAG_NONE, and then
+        // `stop_worker()` could dead lock with this function.
+        while (!job->finish_p && !stop_worker_p) {
+            rb_native_cond_wait(&mjit_worker_wakeup, &mjit_engine_mutex);
+            verbose(3, "Getting wakeup from client");
+        }
+        CRITICAL_SECTION_FINISH(3, "in MJIT copy job wait");
     }
 
-    if (!rb_workqueue_register(0, mjit_copy_job_handler, (void *)job))
-        return false;
-    CRITICAL_SECTION_START(3, "in MJIT copy job wait");
-    /* checking `stop_worker_p` too because `RUBY_VM_CHECK_INTS(ec)` may not
-       lush mjit_copy_job_handler when EC_EXEC_TAG() is not TAG_NONE, and then
-       `stop_worker()` could dead lock with this function. */
-    while (!job->finish_p && !stop_worker_p) {
-        rb_native_cond_wait(&mjit_worker_wakeup, &mjit_engine_mutex);
-        verbose(3, "Getting wakeup from client");
-    }
-    CRITICAL_SECTION_FINISH(3, "in MJIT copy job wait");
-    return job->finish_p;
+    // Set result values.
+    *cc_entries = job->cc_entries;
+    *is_entries = job->is_entries;
+
+    bool result = job->finish_p;
+    CRITICAL_SECTION_START(3, "in copy_cache_from_main_thread");
+    job->iseq = NULL; // Skip `mjit_mark`-ing this ISeq to allow GC
+    // Disable dispatching this job in mjit_copy_job_handler while memory allocated by alloca
+    // could be expired after finishing this function.
+    job->finish_p = true;
+    CRITICAL_SECTION_FINISH(3, "in copy_cache_from_main_thread");
+    return result;
 }
 
 /* The function implementing a worker. It is executed in a separate
@@ -1176,8 +1209,6 @@ copy_cache_from_main_thread(mjit_copy_jo https://github.com/ruby/ruby/blob/trunk/mjit_worker.c#L1209
 void
 mjit_worker(void)
 {
-    mjit_copy_job_t *job = &mjit_copy_job; /* just a shorthand */
-
 #ifndef _MSC_VER
     if (pch_status == PCH_NOT_READY) {
         make_pch();
@@ -1204,28 +1235,19 @@ mjit_worker(void) https://github.com/ruby/ruby/blob/trunk/mjit_worker.c#L1235
             verbose(3, "Getting wakeup from client");
         }
         unit = get_from_list(&unit_queue);
-        if (unit) job->iseq = unit->iseq;
-        job->finish_p = true; // disable dispatching this job in mjit_copy_job_handler while it's being modified
         CRITICAL_SECTION_FINISH(3, "in worker dequeue");
 
         if (unit) {
-            const struct rb_iseq_constant_body *body = unit->iseq->body;
-            job->cc_entries = NULL;
-            if (body->ci_size > 0 || body->ci_kw_size > 0)
-                job->cc_entries = alloca(sizeof(struct rb_call_cache) * (body->ci_size + body->ci_kw_size));
-            job->is_entries = NULL;
-            if (body->is_size > 0)
-                job->is_entries = alloca(sizeof(union iseq_inline_storage_entry) * body->is_size);
-
-            /* Copy ISeq's inline caches values to avoid race condition. */
-            if (job->cc_entries != NULL || job->is_entries != NULL) {
-                if (copy_cache_from_main_thread(job) == false) {
-                    continue; /* retry postponed_job failure, or stop worker */
-                }
+            struct rb_call_cache *cc_entries;
+            union iseq_inline_storage_entry *is_entries;
+
+            // Copy mutable values from main threads
+            if (copy_cache_from_main_thread(unit->iseq, &cc_entries, &is_entries) == false) {
+                continue; // retry postponed_job failure, or stop worker
             }
 
             // JIT compile
-            mjit_func_t func = convert_unit_to_func(unit, job->cc_entries, job->is_entries);
+            mjit_func_t func = convert_unit_to_func(unit, cc_entries, is_entries);
 
             CRITICAL_SECTION_START(3, "in jit func replace");
             while (in_gc) { /* Make sure we're not GC-ing when touching ISeq */
@@ -1248,10 +1270,6 @@ mjit_worker(void) https://github.com/ruby/ruby/blob/trunk/mjit_worker.c#L1270
         }
     }
 
-    // Disable dispatching this job in mjit_copy_job_handler while memory allocated by alloca
-    // could be expired after finishing this function.
-    job->finish_p = true;
-
     // To keep mutex unlocked when it is destroyed by mjit_finish, don't wrap CRITICAL_SECTION here.
     worker_stopped = true;
 }

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