[ruby-dev:11210] Re: Thread.new with irb (PR#20)

まつもと ゆきひろです

In message "Re: Thread.new with irb (PR#20)"
    on 00/10/14, [e-mail] <[e-mail]> writes:

|In the message of "Thread.new with irb"
|    on 2000/10/11 22:41 Katsuyuki Komatsu <[e-mail]> wrote:
|> irbで"p Thread.new"を実行するとSegmentation faultになりました．

|なお，
|    [ruby-dev:11205] Re: ruby-bugs-ja PR#20
|で西山さんが，同じ問題を短いスクリプトで再現されました．
|記録のためruby-bugs-jaにも送ります．

というわけで、このスクリプトのおかげで問題が発見できました。
要するにエラーが発生した Thread.start で作られた中途半端なス
レッドがタイミングによって消滅する前に実行権を奪い取ってしま
う(し、初期化されてないのであちこち壊してまわる)のが原因でし
た。スレッドのバグは再現性が低くて困りますね。

パッチです。

--- eval.c	2000/10/13 09:01:53	1.119
+++ eval.c	2000/10/13 18:39:51
@@ -666,3 +666,2 @@
     while (vars) {
-	if (TYPE(vars) != T_VARMAP) abort();
 	if (curr && vars->id == 0) {
@@ -731,2 +730,3 @@
     struct tag *prev;
+    int line;
 };
@@ -744,2 +744,3 @@
     _tag.dst = 0;			\
+    _tag.line = __LINE__;		\
     prot_tag = &_tag;
@@ -800,2 +801,3 @@
 static rb_thread_t curr_thread = 0;
+static rb_thread_t main_thread;
 static void scope_dup _((struct SCOPE *));
@@ -870,4 +872,4 @@
 {
-    VALUE errat = Qnil;
-    VALUE eclass;
+    VALUE errat = Qnil;		/* OK */
+    volatile VALUE eclass;
     char *einfo;
@@ -4839,3 +4841,3 @@
 	if (state) JUMP_TAG(state);
-	
+
 	return result;
@@ -4932,3 +4934,3 @@
     volatile VALUE wrapper = 0;
-    VALUE self = ruby_top_self;
+    volatile VALUE self = ruby_top_self;
     TMP_PROTECT;
@@ -6148,3 +6150,3 @@
 {
-    VALUE block = rb_eval(self, node->nd_body);
+    VALUE block = rb_eval(self, node->nd_body);	/* OK */
     struct BLOCK * volatile old_block;
@@ -6625,5 +6627,2 @@
 
-static rb_thread_t main_thread;
-/*static rb_thread_t curr_thread = 0;*/
-
 #define FOREACH_THREAD_FROM(f,x) x = f; do { x = x->next;
@@ -6756,3 +6755,2 @@
     VALUE *pos;
-
     int len;
@@ -7007,3 +7005,2 @@
 {
-    struct stat s;
     int i, test = Qfalse;
@@ -7302,3 +7299,2 @@
     double limit;
-    struct timeval zero;
     int n;
@@ -7645,2 +7641,5 @@
 \
+    th->next = 0;\
+    th->prev = 0;\
+\
     th->status = THREAD_RUNNABLE;\
@@ -7675,3 +7674,2 @@
     th->gid = 1;\
-    th->locals = 0;\
 } while(0)
@@ -7688,15 +7686,2 @@
 
-    if (curr_thread) {
-	th->prev = curr_thread;
-	curr_thread->next->prev = th;
-	th->next = curr_thread->next;
-	curr_thread->next = th;
-	th->priority = curr_thread->priority;
-	th->gid = curr_thread->gid;
-    }
-    else {
-	curr_thread = th->prev = th->next = th;
-	th->status = THREAD_RUNNABLE;
-    }
-
     for (vars = th->dyna_vars; vars; vars = vars->next) {
@@ -7708,2 +7693,14 @@
 
+static void
+rb_thread_add_ring(th)
+    rb_thread_t th;
+{
+    th->prev = curr_thread;
+    curr_thread->next->prev = th;
+    th->next = curr_thread->next;
+    curr_thread->next = th;
+    th->priority = curr_thread->priority;
+    th->gid = curr_thread->gid;
+}
+
 #if defined(HAVE_SETITIMER)
@@ -7760,7 +7757,8 @@
 static VALUE
-rb_thread_start_0(fn, arg, th)
+rb_thread_start_0(fn, arg, th_arg)
     VALUE (*fn)();
     void *arg;
-    rb_thread_t th;
+    rb_thread_t th_arg;
 {
+    volatile rb_thread_t th = th_arg;
     volatile VALUE thread = th->thread;
@@ -7793,6 +7791,11 @@
     if ((state = EXEC_TAG()) == 0) {
-	if (THREAD_SAVE_CONTEXT(th) == 0) {
+#if 0
+	if ((status = THREAD_SAVE_CONTEXT(th)) == 0) {
+#endif
 	    curr_thread = th;
 	    th->result = (*fn)(arg, th);
+	    rb_thread_remove(th);
+#if 0
 	}
+#endif
     }
@@ -7800,3 +7803,2 @@
     status = th->status;
-    rb_thread_remove(th);
     if (state && status != THREAD_TO_KILL && !NIL_P(ruby_errinfo)) {
@@ -7835,3 +7837,5 @@
 {
-    return rb_thread_start_0(fn, arg, rb_thread_alloc(rb_cThread));
+    rb_thread_t th = rb_thread_alloc(rb_cThread);
+    rb_thread_add_ring(th);
+    return rb_thread_start_0(fn, arg, th);
 }
@@ -7866,3 +7870,3 @@
     if (th->stk_pos == pos) {
-	rb_raise(rb_eThreadError, "uninitialized thread - check `initialize' of %s",
+	rb_raise(rb_eThreadError, "uninitialized thread - check `%s#initialize'",
 		 rb_class2name(klass));
@@ -7877,2 +7881,4 @@
 {
+    rb_thread_t th;
+
     if (!rb_block_given_p()) {
@@ -7880,3 +7886,5 @@
     }
-    return rb_thread_start_0(rb_thread_yield, args, rb_thread_check(thread));
+    th = rb_thread_check(thread);
+    rb_thread_add_ring(th);
+    return rb_thread_start_0(rb_thread_yield, args, th);
 }
@@ -7887,2 +7895,4 @@
 {
+    rb_thread_t th;
+
     if (!rb_block_given_p()) {
@@ -7890,3 +7900,5 @@
     }
-    return rb_thread_start_0(rb_thread_yield, args, rb_thread_alloc(klass));
+    th = rb_thread_alloc(rb_cThread);
+    rb_thread_add_ring(th);
+    return rb_thread_start_0(rb_thread_yield, args, th);
 }
@@ -8094,2 +8106,3 @@
     rb_thread_raise(argc, argv, th);
+    return Qnil;		/* not reached */
 }
@@ -8172,3 +8185,3 @@
     rb_thread_t th = rb_thread_check(thread);
-    char *s, *status;
+    char *status;
     VALUE str;
@@ -8207,4 +8220,4 @@
     THREAD_ALLOC(th);
-    cont = Data_Wrap_Struct(rb_cCont, thread_mark,
-					 thread_free, th);
+    th->status = THREAD_RUNNABLE;
+    cont = Data_Wrap_Struct(rb_cCont, thread_mark, thread_free, th);
 
@@ -8367,2 +8380,3 @@
     main_thread = rb_thread_alloc(rb_cThread);
+    curr_thread = main_thread->prev = main_thread->next = main_thread;
 
@@ -8480,2 +8494 @@
 }
-