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thread_sync: redo r62934 to use fork_gen
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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
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@tenderlove
normal authored and tenderlove committed Jul 24, 2018
1 parent 945bf91 commit ca9b30a
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Showing 2 changed files with 33 additions and 62 deletions.
1 change: 0 additions & 1 deletion thread.c
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Expand Up @@ -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();
Expand Down
94 changes: 33 additions & 61 deletions thread_sync.c
View file
Expand Up @@ -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);

Expand Down Expand Up @@ -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;
Expand All @@ -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)
{
Expand All @@ -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
};

Expand All @@ -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;
}

Expand All @@ -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)
{
Expand All @@ -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
};

Expand All @@ -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;
}

Expand All @@ -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;
}

Expand Down Expand Up @@ -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;
};

/*
Expand Down Expand Up @@ -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)
{
Expand All @@ -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;
}

Expand All @@ -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;
}
Expand Down Expand Up @@ -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)
{
Expand Down

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