Feature #17: deadlock detection for 1.9

• Status: Closed
• Assignee: mame (Yusuke Endoh)
• Target version: -

[mame (Yusuke Endoh)]

=begin
遠藤です。

redmine から投稿してみます。

1.9 のスレッドにデッドロック検出を実装してみました。

• スレッドの状態種別に THREAD_STOPPED_FOREVER を追加。
  無期限の sleep 状態と mutex 解放待ち状態を表す。

• rb_vm_t に変数 sleeper を追加。
  THREAD_STOPPED_FOREVER 状態のスレッドの数を表す。

• rb_thread_t に変数 locking_mutex を追加。
  このスレッドが待っている mutex を表す。

• rb_thread_t に st_table *keeping_mutexes を追加。
  このスレッドがロックしている mutex たちを表す。

• mutex_t に変数 cond_notified を追加。
  cond_signal されてまだ起動していないスレッドの数を表す。

• スレッドの終了時にロックしていた mutex をすべて
  解放するようにした。

• rb_mutex_lock や rb_mutex_unlock で追加した変数たちを
  適宜更新するようにした。

• 唯一動いていそうなスレッドが native_cond_wait しそうな
  時は、lock_func を抜けてデッドロック検査するようにした。

• rb_check_deadlock では vm->living_threads を列挙して、

  • 例外状態のスレッド、または
  • locking_mutex のロックに成功したスレッド、または
  • locking_mutex が誰にもロックされていないスレッド、
    のいずれもなければ main_thread にデッドロックを投げる
    ようにした。

どんなもんでしょう。

Index: thread_pthread.c

--- thread_pthread.c (revision 16676)
+++ thread_pthread.c (working copy)
@@ -418,7 +418,14 @@
}
}

• th->status = THREAD_STOPPED;

• if (tv) {

• th->status = THREAD_STOPPED;

• }

• else {

• th->status = THREAD_STOPPED_FOREVER;

• th->vm->sleeper++;

• rb_check_deadlock(th->vm);

• }

  thread_debug("native_sleep %ld\n", tv ? tv->tv_sec : -1);
  GVL_UNLOCK_BEGIN();
  @@ -455,9 +462,10 @@
  th->unblock_function_arg = 0;

pthread_mutex_unlock(&th->interrupt_lock);

• th->status = prev_status;
  }
  GVL_UNLOCK_END();

• th->status = prev_status;

• if (!tv) th->vm->sleeper--;
  RUBY_VM_CHECK_INTS();

  thread_debug("native_sleep done\n");
  Index: bootstraptest/test_thread.rb
  ===================================================================
  --- bootstraptest/test_thread.rb (revision 16676)
  +++ bootstraptest/test_thread.rb (working copy)
  @@ -268,3 +268,66 @@
  at_exit { Fiber.new{}.resume }
  }

+assert_equal 'ok', %q{

• begin
• Thread.new { sleep }
• sleep
• :ng
• rescue Exception
• :ok
• end
  +}

+assert_equal 'ok', %q{

• begin
• m1, m2 = Mutex.new, Mutex.new
• Thread.new { m1.lock; sleep 1; m2.lock }
• m2.lock; sleep 1; m1.lock
• sleep
• :ng
• rescue Exception
• :ok
• end
  +}

+assert_equal 'ok', %q{

• begin
• m = Mutex.new
• Thread.new { m.lock }; m.lock
• :ok
• rescue Exception
• :ng
• end
  +}

+assert_equal 'ok', %q{

• begin
• m = Mutex.new
• Thread.new { m.lock }.join; m.lock
• :ok
• rescue Exception
• :ng
• end
  +}

+assert_equal 'ok', %q{

• begin
• m = Mutex.new
• Thread.new { m.lock; sleep 2 }
• sleep 1; m.lock
• :ok
• rescue Exception
• :ng
• end
  +}

+assert_equal 'ok', %q{

• begin

• m = Mutex.new

• Thread.new { m.lock; sleep 2; m.unlock }

• sleep 1; m.lock

• :ok

• rescue Exception

• :ng

• end
  +}
  Index: vm_core.h
  ===================================================================
  --- vm_core.h (revision 16676)
  +++ vm_core.h (working copy)
  @@ -300,6 +300,7 @@
  int running;
  int thread_abort_on_exception;
  unsigned long trace_flag;

• volatile int sleeper;

  /* object management */
  VALUE mark_object_ary;
  @@ -354,6 +355,7 @@
  THREAD_TO_KILL,
  THREAD_RUNNABLE,
  THREAD_STOPPED,

• THREAD_STOPPED_FOREVER,
  THREAD_KILLED,
  };

@@ -421,6 +423,8 @@
rb_unblock_function_t *unblock_function;
void *unblock_function_arg;
rb_thread_lock_t interrupt_lock;

• VALUE locking_mutex;

• st_table *keeping_mutexes;

  struct rb_vm_tag *tag;
  struct rb_vm_trap_tag *trap_tag;
  Index: thread.c
  ===================================================================
  --- thread.c (revision 16676)
  +++ thread.c (working copy)
  @@ -62,6 +62,9 @@
  struct timeval rb_time_interval(VALUE);
  static int rb_thread_dead(rb_thread_t *th);

+static int unlock_i(st_data_t key, st_data_t val, rb_thread_t *th);
+static void rb_check_deadlock(rb_vm_t *vm);
+
void rb_signal_exec(rb_thread_t *th, int sig);
void rb_disable_interrupt(void);

@@ -92,13 +95,13 @@
rb_thread_set_current(_th_stored);
} while(0)

-#define BLOCKING_REGION(exec, ubf, ubfarg) do {
+#define BLOCKING_REGION(exec, ubf, ubfarg, stopped) do {
rb_thread_t *__th = GET_THREAD();
int __prev_status = __th->status;
rb_unblock_function_t *__oldubf;
void *__oldubfarg;
set_unblock_function(__th, ubf, ubfarg, &__oldubf, &__oldubfarg); \

• __th->status = THREAD_STOPPED; \

• if (stopped) __th->status = THREAD_STOPPED;
  thread_debug("enter blocking region (%p)\n", __th);
  GVL_UNLOCK_BEGIN(); {
  exec;
  @@ -107,10 +110,9 @@
  thread_debug("leave blocking region (%p)\n", __th);
  remove_signal_thread_list(__th);
  set_unblock_function(__th, __oldubf, __oldubfarg, 0, 0); \

• if (__th->status == THREAD_STOPPED) { \

• if (stopped && __th->status == THREAD_STOPPED) {
  __th->status = __prev_status;
  } \

• RUBY_VM_CHECK_INTS();
  } while(0)

#if THREAD_DEBUG
@@ -197,19 +199,11 @@
set_unblock_function(rb_thread_t *th, rb_unblock_function_t *func, void *arg,
rb_unblock_function_t **oldfunc, void **oldarg)
{

• check_ints:
• RUBY_VM_CHECK_INTS(); /* check signal or so */
  native_mutex_lock(&th->interrupt_lock);
• if (th->interrupt_flag) {
• native_mutex_unlock(&th->interrupt_lock);
• goto check_ints;
• }
• else {
• if (oldfunc) *oldfunc = th->unblock_function;
• if (oldarg) *oldarg = th->unblock_function_arg;
• th->unblock_function = func;
• th->unblock_function_arg = arg;
• }

• if (oldfunc) *oldfunc = th->unblock_function;
• if (oldarg) *oldarg = th->unblock_function_arg;
• th->unblock_function = func;
• th->unblock_function_arg = arg;
  native_mutex_unlock(&th->interrupt_lock);
  }

@@ -259,6 +253,11 @@
thread_debug("rb_thread_terminate_all (main thread: %p)\n", th);
st_foreach(vm->living_threads, terminate_i, (st_data_t)th);

• /* unlock all locking mutexes */

• if (th->keeping_mutexes) {

• st_foreach(th->keeping_mutexes, unlock_i, 0);

• }

• while (!rb_thread_alone()) {
  PUSH_TAG();
  if (EXEC_TAG() == 0) {
  @@ -354,6 +353,17 @@
  }
  TH_POP_TAG();

• /* locking_mutex must be Qfalse */

• if (th->locking_mutex != Qfalse) {

•  rb_bug("thread_start_func_2: locking_mutex must be NULL (%p:%p)", th, (void*)th->locking_mutex);
  

• }

• /* unlock all locking mutexes */

• if (th->keeping_mutexes) {

•  st_foreach(th->keeping_mutexes, unlock_i, 0);
  

• }

• /* delete self from living_threads */
  st_delete_wrap(th->vm->living_threads, th->self);

  /* wake up joinning threads */
  @@ -363,7 +373,7 @@
  rb_thread_interrupt(join_th);
  join_th = join_th->join_list_next;
  }

• st_delete_wrap(th->vm->living_threads, th->self);

• rb_check_deadlock(th->vm);

  if (!th->root_fiber) {
  rb_thread_recycle_stack_release(th->stack);
  @@ -775,7 +785,8 @@

  BLOCKING_REGION({
  val = func(data1);

• }, ubf, data2);

• }, ubf, data2, 1);

• RUBY_VM_CHECK_INTS();

  return val;
  }
  @@ -1135,6 +1146,7 @@
  switch (th->status) {
  case THREAD_RUNNABLE:
  case THREAD_STOPPED:

•  case THREAD_STOPPED_FOREVER:
   case THREAD_TO_KILL:
  

  rb_ary_push(ary, th->self);
  default:
  @@ -1329,6 +1341,7 @@
  case THREAD_RUNNABLE:
  return "run";
  case THREAD_STOPPED:

•  case THREAD_STOPPED_FOREVER:
  

  return "sleep";
  case THREAD_TO_KILL:
  return "aborting";
  @@ -1428,7 +1441,7 @@

  if (rb_thread_dead(th))
  return Qtrue;

• if (th->status == THREAD_STOPPED)

• if (th->status == THREAD_STOPPED || th->status == THREAD_STOPPED_FOREVER)
  return Qtrue;
  return Qfalse;
  }
  @@ -1868,14 +1881,16 @@
  if (except) *except = orig_except;
  wait = &wait_100ms;
  } while (__th->interrupt_flag == 0 && (timeout == 0 || subst(timeout, &wait_100ms)));

•  }, 0, 0);
  

•  }, 0, 0, 1);
  

•  RUBY_VM_CHECK_INTS();
  

  } while (result == 0 && (timeout == 0 || subst(timeout, &wait_100ms)));
  }
  #else
  BLOCKING_REGION({
  result = select(n, read, write, except, timeout);
  if (result < 0) lerrno = errno;

• }, ubf_select, GET_THREAD());

• }, ubf_select, GET_THREAD(), 1);

• RUBY_VM_CHECK_INTS();
  #endif

  errno = lerrno;
  @@ -2070,6 +2085,7 @@
  st_foreach(vm->living_threads, terminate_atfork_i, (st_data_t)th);
  st_clear(vm->living_threads);
  st_insert(vm->living_threads, thval, (st_data_t) th->thread_id);

• vm->sleeper = 0;
  }

static int
@@ -2096,6 +2112,7 @@
st_foreach(vm->living_threads, terminate_atfork_before_exec_i, (st_data_t)th);
st_clear(vm->living_threads);
st_insert(vm->living_threads, thval, (st_data_t) th->thread_id);

• vm->sleeper = 0;
  }

struct thgroup {
@@ -2312,7 +2329,7 @@
rb_thread_lock_t lock;
rb_thread_cond_t cond;
rb_thread_t volatile *th;

• volatile int cond_waiting;

• volatile int cond_waiting, cond_notified;
  } mutex_t;

#define GetMutexPtr(obj, tobj)
@@ -2384,6 +2401,15 @@
return mutex->th ? Qtrue : Qfalse;
}

+static void
+mutex_locked(rb_thread_t *th, VALUE self)
+{

• if (!th->keeping_mutexes) {
• th->keeping_mutexes = st_init_numtable();
• }
• st_insert(th->keeping_mutexes, self, (st_data_t) th->thread_id);
  +}

/*

• call-seq:
• mutex.try_lock => true or false
  @@ -2406,6 +2432,8 @@
  if (mutex->th == 0) {
  mutex->th = GET_THREAD();
  locked = Qtrue;

• mutex_locked(GET_THREAD(), self);
  }
  native_mutex_unlock(&mutex->lock);

@@ -2413,17 +2441,23 @@
}

static int
-lock_func(rb_thread_t *th, mutex_t *mutex)
+lock_func(rb_thread_t *th, mutex_t *mutex, int last_thread)
{
int interrupted = Qfalse;

  native_mutex_lock(&mutex->lock);
  while (mutex->th || (mutex->th = th, 0)) {

• if (last_thread) {

•  interrupted = 2;
  

•  break;
  

• }
• mutex->cond_waiting++;
  native_cond_wait(&mutex->cond, &mutex->lock);
• mutex->cond_notified--;

• if (th->interrupt_flag) {

•  interrupted = Qtrue;
  

• if (RUBY_VM_INTERRUPTED(th)) {

•  interrupted = 1;
   break;
  

  }
  }
  @@ -2438,6 +2472,7 @@
  native_mutex_lock(&mutex->lock);
  if (mutex->cond_waiting > 0) {
  native_cond_broadcast(&mutex->cond);

• mutex->cond_notified += mutex->cond_waiting;
  mutex->cond_waiting = 0;
  }
  native_mutex_unlock(&mutex->lock);
  @@ -2460,11 +2495,30 @@

  while (mutex->th != th) {
  int interrupted;

•  int prev_status = th->status;
  

•  int last_thread = 0;
  

•  th->locking_mutex = self;
  

•  th->status = THREAD_STOPPED_FOREVER;
  

•  th->vm->sleeper++;
  

•  if (th->vm->living_threads->num_entries == th->vm->sleeper) {
  

•  last_thread = 1;
  

•  }
  

•  BLOCKING_REGION({
  

•  interrupted = lock_func(th, mutex);
  

•  }, lock_interrupt, mutex);
  

•  interrupted = lock_func(th, mutex, last_thread);
  

•  }, lock_interrupt, mutex, 0);
  

•  th->locking_mutex = Qfalse;
  

•  if (interrupted == 2) {
  

•  /* assert: mutex->th != th */
  

•  rb_check_deadlock(th->vm);
  

•  }
  

•  th->status = prev_status;
  

•  th->vm->sleeper--;
  

•  if (mutex->th == th) mutex_locked(th, self);
  

•  if (interrupted) {
   RUBY_VM_CHECK_INTS();
   }
  

@@ -2473,15 +2527,8 @@
return self;
}

-/*

• • call-seq:
• • mutex.unlock => self
• • Releases the lock.
• • Raises +ThreadError+ if +mutex+ wasn't locked by the current thread.
• */
  -VALUE
  -rb_mutex_unlock(VALUE self)
  +static char *
  +mutex_unlock(VALUE self)
  {
  mutex_t *mutex;
  char err = NULL;
  @@ -2501,16 +2548,45 @@
  / waiting thread */
  native_cond_signal(&mutex->cond);
  mutex->cond_waiting--;

•  mutex->cond_notified++;
  

  }
  }

  native_mutex_unlock(&mutex->lock);

• return err;
  +}

+/*

• • call-seq:
• • mutex.unlock => self
• • Releases the lock.
• • Raises +ThreadError+ if +mutex+ wasn't locked by the current thread.

• */
  +VALUE
  +rb_mutex_unlock(VALUE self)
  +{

• char *err;

• err = mutex_unlock(self);

• if (!err) st_delete_wrap(GET_THREAD()->keeping_mutexes, self);
  if (err) rb_raise(rb_eThreadError, err);

  return self;
  }

+static int
+unlock_i(st_data_t key, st_data_t val, rb_thread_t *th)
+{

• VALUE mtxval = key;
• mutex_unlock(mtxval);
• return ST_CONTINUE;
  +}

static VALUE
rb_mutex_sleep_forever(VALUE time)
{
@@ -2579,6 +2655,51 @@
return rb_ensure(func, arg, rb_mutex_unlock, mutex);
}

+static int
+check_deadlock_i(st_data_t key, st_data_t val, int *found)
+{

• VALUE thval = key;
• rb_thread_t *th;
• GetThreadPtr(thval, th);
• if (th->status != THREAD_STOPPED_FOREVER) {
• rb_bug("check_deadlock_i: thread that is not THREAD_STOPPED_FOREVER found (%p:%d)", th, th->status);
• }
• if (RUBY_VM_INTERRUPTED(th)) {
• *found = 1;
• }
• else if (th->locking_mutex) {
• mutex_t *mutex;
• GetMutexPtr(th->locking_mutex, mutex);
• native_mutex_lock(&mutex->lock);
• if (mutex->th == th || (!mutex->th && mutex->cond_notified)) {

•  *found = 1;
  

• }
• native_mutex_unlock(&mutex->lock);
• }
• return (*found) ? ST_STOP : ST_CONTINUE;
  +}

+static void
+rb_check_deadlock(rb_vm_t *vm)
+{

• int found = 0;
• if (vm->living_threads->num_entries != vm->sleeper) return;
• st_foreach(vm->living_threads, check_deadlock_i, (st_data_t)&found);
• if (!found) {
• VALUE argv[2];
• argv[0] = rb_eFatal;
• argv[1] = rb_str_new2("deadlock detected");
• rb_thread_raise(2, argv, vm->main_thread);
• }
  +}

/*

• Document-class: Barrier
  */
  Index: vm.c
  ===================================================================
  --- vm.c (revision 16676)
  +++ vm.c (working copy)
  @@ -1445,6 +1445,13 @@
  RUBY_FREE_UNLESS_NULL(th->stack);
  }

• if (th->locking_mutex != Qfalse) {

•  rb_bug("thread_free: locking_mutex must be NULL (%p:%d)", th, th->locking_mutex);
  

• }

• if (th->keeping_mutexes) {

•  st_free_table(th->keeping_mutexes);
  

• }

• if (th->local_storage) {
  st_free_table(th->local_storage);
  }
  @@ -1512,6 +1519,12 @@
  RUBY_MARK_UNLESS_NULL(th->root_fiber);
  RUBY_MARK_UNLESS_NULL(th->stat_insn_usage);

• RUBY_MARK_UNLESS_NULL(th->locking_mutex);

• if (th->keeping_mutexes) {

•  st_foreach(th->keeping_mutexes, vm_mark_each_thread_func, 0);
  

• }

• rb_mark_tbl(th->local_storage);

  if (GET_THREAD() != th && th->machine_stack_start && th->machine_stack_end) {

--
Yusuke ENDOH [e-mail]
=end

[mame (Yusuke Endoh)]

• Status changed from Open to Closed
• Assignee changed from ko1 (Koichi Sasada) to mame (Yusuke Endoh)

=begin
integrated in r17110
=end