From: Yusuke ENDOH <mame@...>
Date: 2010-01-21T23:10:07+09:00
Subject: [ruby-dev:40121] [Bug:trunk] cannot resume Fiber from forked process

遠藤です。

fork の子プロセスから元プロセスの Fiber が呼べません。

  $ ./ruby -e '
  f = Fiber.new { }
  fork { f.resume }
  Process.waitpid
  '
  -e:3:in `resume': fiber called across trap (FiberError)
          from -e:3:in `block in <main>'
          from -e:3:in `fork'
          from -e:3:in `<main>'

そういう仕様ならそういう仕様で別に構わないのですが、fiber
called across *trap* という例外メッセージはおかしい気がします。

ちなみに、trap をまたがって Fiber を呼ぶことは可能なようです。

  $ ./ruby -e '
  f = Fiber.new { p :ok }
  trap(:USR1) { f.resume }
  Process.kill :USR1, $$
  sleep 0.2
  '
  :ok

  $ ./ruby -e '
  f = nil
  trap(:USR1) { f = Fiber.new { p :ok } }
  Process.kill :USR1, $$
  sleep 0.2
  f.resume
  '
  :ok

このチェックはもう必要ないのではないでしょうか。反対がなければ
コミットしようと思います。

diff --git a/cont.c b/cont.c
index a77f35e..932b10e 100644
--- a/cont.c
+++ b/cont.c
@@ -388,7 +388,6 @@ cont_restore_1(rb_context_t *cont)
     th->state = sth->state;
     th->status = sth->status;
     th->tag = sth->tag;
-    th->trap_tag = sth->trap_tag;
     th->errinfo = sth->errinfo;
     th->first_proc = sth->first_proc;

@@ -621,9 +620,6 @@ rb_cont_call(int argc, VALUE *argv, VALUE contval)
     if (cont->saved_thread.self != th->self) {
 	rb_raise(rb_eRuntimeError, "continuation called across threads");
     }
-    if (cont->saved_thread.trap_tag != th->trap_tag) {
-	rb_raise(rb_eRuntimeError, "continuation called across trap");
-    }
     if (cont->saved_thread.fiber) {
 	rb_fiber_t *fcont;
 	GetFiberPtr(cont->saved_thread.fiber, fcont);
@@ -940,9 +936,6 @@ fiber_switch(VALUE fibval, int argc, VALUE *argv,
int is_resume)
     if (cont->saved_thread.self != th->self) {
 	rb_raise(rb_eFiberError, "fiber called across threads");
     }
-    else if (cont->saved_thread.trap_tag != th->trap_tag) {
-	rb_raise(rb_eFiberError, "fiber called across trap");
-    }
     else if (fib->status == TERMINATED) {
 	value = rb_exc_new2(rb_eFiberError, "dead fiber called");
 	if (th->fiber != fibval) rb_exc_raise(value);
diff --git a/eval.c b/eval.c
index c5a72dc..aa01d81 100644
--- a/eval.c
+++ b/eval.c
@@ -677,19 +677,14 @@ rb_protect(VALUE (* proc) (VALUE), VALUE data,
int * state)
     int status;
     rb_thread_t *th = GET_THREAD();
     rb_control_frame_t *cfp = th->cfp;
-    struct rb_vm_trap_tag trap_tag;
     rb_jmpbuf_t org_jmpbuf;

-    trap_tag.prev = th->trap_tag;
-
     PUSH_TAG();
-    th->trap_tag = &trap_tag;
     MEMCPY(&org_jmpbuf, &(th)->root_jmpbuf, rb_jmpbuf_t, 1);
     if ((status = EXEC_TAG()) == 0) {
 	SAVE_ROOT_JMPBUF(th, result = (*proc) (data));
     }
     MEMCPY(&(th)->root_jmpbuf, &org_jmpbuf, rb_jmpbuf_t, 1);
-    th->trap_tag = trap_tag.prev;
     POP_TAG();

     if (state) {
diff --git a/vm_core.h b/vm_core.h
index b9b584a..b781765 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -347,10 +347,6 @@ struct rb_vm_tag {
     struct rb_vm_tag *prev;
 };

-struct rb_vm_trap_tag {
-    struct rb_vm_trap_tag *prev;
-};
-
 #define RUBY_VM_VALUE_CACHE_SIZE 0x1000
 #define USE_VALUE_CACHE 0

@@ -414,7 +410,6 @@ typedef struct rb_thread_struct
     int transition_for_lock;

     struct rb_vm_tag *tag;
-    struct rb_vm_trap_tag *trap_tag;

     int parse_in_eval;
     int mild_compile_error;

-- 
Yusuke ENDOH <mame@tsg.ne.jp>