thread_sync: redo r62934 to use fork_gen

normal · tenderlove · commit ca9b30a36578 · 2018-07-24T11:05:37.000-07:00
Instead of maintaining linked-lists to store all
rb_queue/rb_szqueue/rb_condvar structs; store only a fork_gen
serial number to simplify management of these items.

This reduces initialization costs and avoids the up-front cost
of resetting all Queue/SizedQueue/ConditionVariable objects at
fork while saving 8 bytes per-structure on 64-bit.  There are no
savings on 32-bit.

* thread.c (rb_thread_atfork_internal): remove rb_thread_sync_reset_all call
* thread_sync.c (rb_thread_sync_reset_all): remove
* thread_sync.c (queue_live): remove
* thread_sync.c (queue_free): remove
* thread_sync.c (struct rb_queue): s/live/fork_gen/
* thread_sync.c (queue_data_type): use default free
* thread_sync.c (queue_alloc): remove list_add
* thread_sync.c (queue_fork_check): new function
* thread_sync.c (queue_ptr): call queue_fork_check
* thread_sync.c (szqueue_free): remove
* thread_sync.c (szqueue_data_type): use default free
* thread_sync.c (szqueue_alloc): remove list_add
* thread_sync.c (szqueue_ptr):  check fork_gen via queue_fork_check
* thread_sync.c (struct rb_condvar): s/live/fork_gen/
* thread_sync.c (condvar_free): remove
* thread_sync.c (cv_data_type): use default free
* thread_sync.c (condvar_ptr): check fork_gen
* thread_sync.c (condvar_alloc): remove list_add
  [ruby-core:86316] [Bug #14634]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63215 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
diff --git a/thread.c b/thread.c
@@ -4189,7 +4189,6 @@ rb_thread_atfork_internal(rb_thread_t *th, void (*atfork)(rb_thread_t *, const r
     rb_vm_living_threads_init(vm);
     rb_vm_living_threads_insert(vm, th);
     vm->fork_gen++;
-    rb_thread_sync_reset_all();
 
     vm->sleeper = 0;
     clear_coverage();
diff --git a/thread_sync.c b/thread_sync.c
@@ -62,7 +62,6 @@ typedef struct rb_mutex_struct {
 static void rb_mutex_abandon_all(rb_mutex_t *mutexes);
 static void rb_mutex_abandon_keeping_mutexes(rb_thread_t *th);
 static void rb_mutex_abandon_locking_mutex(rb_thread_t *th);
-static void rb_thread_sync_reset_all(void);
 #endif
 static const char* rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t volatile *th);
 
@@ -544,17 +543,15 @@ void rb_mutex_allow_trap(VALUE self, int val)
 /* Queue */
 
 #define queue_waitq(q) UNALIGNED_MEMBER_PTR(q, waitq)
-#define queue_live(q) UNALIGNED_MEMBER_PTR(q, live)
 PACKED_STRUCT_UNALIGNED(struct rb_queue {
-    struct list_node live;
     struct list_head waitq;
+    rb_serial_t fork_gen;
     const VALUE que;
     int num_waiting;
 });
 
 #define szqueue_waitq(sq) UNALIGNED_MEMBER_PTR(sq, q.waitq)
 #define szqueue_pushq(sq) UNALIGNED_MEMBER_PTR(sq, pushq)
-#define szqueue_live(sq) UNALIGNED_MEMBER_PTR(sq, q.live)
 PACKED_STRUCT_UNALIGNED(struct rb_szqueue {
     struct rb_queue q;
     int num_waiting_push;
@@ -571,14 +568,6 @@ queue_mark(void *ptr)
     rb_gc_mark(q->que);
 }
 
-static void
-queue_free(void *ptr)
-{
-    struct rb_queue *q = ptr;
-    list_del(queue_live(q));
-    ruby_xfree(ptr);
-}
-
 static size_t
 queue_memsize(const void *ptr)
 {
@@ -587,7 +576,7 @@ queue_memsize(const void *ptr)
 
 static const rb_data_type_t queue_data_type = {
     "queue",
-    {queue_mark, queue_free, queue_memsize,},
+    {queue_mark, RUBY_TYPED_DEFAULT_FREE, queue_memsize,},
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY|RUBY_TYPED_WB_PROTECTED
 };
 
@@ -599,16 +588,32 @@ queue_alloc(VALUE klass)
 
     obj = TypedData_Make_Struct(klass, struct rb_queue, &queue_data_type, q);
     list_head_init(queue_waitq(q));
-    list_add(&queue_list, queue_live(q));
     return obj;
 }
 
+static int
+queue_fork_check(struct rb_queue *q)
+{
+    rb_serial_t fork_gen = GET_VM()->fork_gen;
+
+    if (q->fork_gen == fork_gen) {
+        return 0;
+    }
+    /* forked children can't reach into parent thread stacks */
+    q->fork_gen = fork_gen;
+    list_head_init(queue_waitq(q));
+    q->num_waiting = 0;
+    return 1;
+}
+
 static struct rb_queue *
 queue_ptr(VALUE obj)
 {
     struct rb_queue *q;
 
     TypedData_Get_Struct(obj, struct rb_queue, &queue_data_type, q);
+    queue_fork_check(q);
+
     return q;
 }
 
@@ -622,14 +627,6 @@ szqueue_mark(void *ptr)
     queue_mark(&sq->q);
 }
 
-static void
-szqueue_free(void *ptr)
-{
-    struct rb_szqueue *sq = ptr;
-    list_del(szqueue_live(sq));
-    ruby_xfree(ptr);
-}
-
 static size_t
 szqueue_memsize(const void *ptr)
 {
@@ -638,7 +635,7 @@ szqueue_memsize(const void *ptr)
 
 static const rb_data_type_t szqueue_data_type = {
     "sized_queue",
-    {szqueue_mark, szqueue_free, szqueue_memsize,},
+    {szqueue_mark, RUBY_TYPED_DEFAULT_FREE, szqueue_memsize,},
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY|RUBY_TYPED_WB_PROTECTED
 };
 
@@ -650,7 +647,6 @@ szqueue_alloc(VALUE klass)
 					&szqueue_data_type, sq);
     list_head_init(szqueue_waitq(sq));
     list_head_init(szqueue_pushq(sq));
-    list_add(&szqueue_list, szqueue_live(sq));
     return obj;
 }
 
@@ -660,6 +656,11 @@ szqueue_ptr(VALUE obj)
     struct rb_szqueue *sq;
 
     TypedData_Get_Struct(obj, struct rb_szqueue, &szqueue_data_type, sq);
+    if (queue_fork_check(&sq->q)) {
+        list_head_init(szqueue_pushq(sq));
+        sq->num_waiting_push = 0;
+    }
+
     return sq;
 }
 
@@ -1239,10 +1240,9 @@ rb_szqueue_empty_p(VALUE self)
 
 
 /* ConditionalVariable */
-/* TODO: maybe this can be IMEMO */
 struct rb_condvar {
     struct list_head waitq;
-    struct list_node live;
+    rb_serial_t fork_gen;
 };
 
 /*
@@ -1273,14 +1273,6 @@ struct rb_condvar {
  *    }
  */
 
-static void
-condvar_free(void *ptr)
-{
-    struct rb_condvar *cv = ptr;
-    list_del(&cv->live);
-    ruby_xfree(ptr);
-}
-
 static size_t
 condvar_memsize(const void *ptr)
 {
@@ -1289,17 +1281,23 @@ condvar_memsize(const void *ptr)
 
 static const rb_data_type_t cv_data_type = {
     "condvar",
-    {0, condvar_free, condvar_memsize,},
+    {0, RUBY_TYPED_DEFAULT_FREE, condvar_memsize,},
     0, 0, RUBY_TYPED_FREE_IMMEDIATELY|RUBY_TYPED_WB_PROTECTED
 };
 
 static struct rb_condvar *
 condvar_ptr(VALUE self)
 {
     struct rb_condvar *cv;
+    rb_serial_t fork_gen = GET_VM()->fork_gen;
 
     TypedData_Get_Struct(self, struct rb_condvar, &cv_data_type, cv);
 
+    /* forked children can't reach into parent thread stacks */
+    if (cv->fork_gen != fork_gen) {
+        list_head_init(&cv->waitq);
+    }
+
     return cv;
 }
 
@@ -1311,7 +1309,6 @@ condvar_alloc(VALUE klass)
 
     obj = TypedData_Make_Struct(klass, struct rb_condvar, &cv_data_type, cv);
     list_head_init(&cv->waitq);
-    list_add(&condvar_list, &cv->live);
 
     return obj;
 }
@@ -1425,31 +1422,6 @@ define_thread_class(VALUE outer, const char *name, VALUE super)
     return klass;
 }
 
-#if defined(HAVE_WORKING_FORK)
-/* we must not reference stacks of dead threads in a forked child */
-static void
-rb_thread_sync_reset_all(void)
-{
-    struct rb_queue *q = 0;
-    struct rb_szqueue *sq = 0;
-    struct rb_condvar *cv = 0;
-
-    list_for_each(&queue_list, q, live) {
-        list_head_init(queue_waitq(q));
-        q->num_waiting = 0;
-    }
-    list_for_each(&szqueue_list, sq, q.live) {
-        list_head_init(szqueue_waitq(sq));
-        list_head_init(szqueue_pushq(sq));
-        sq->num_waiting_push = 0;
-        sq->q.num_waiting = 0;
-    }
-    list_for_each(&condvar_list, cv, live) {
-        list_head_init(&cv->waitq);
-    }
-}
-#endif
-
 static void
 Init_thread_sync(void)
 {
