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thread_sync.c (rb_mutex_cleanup_keeping_mutexes): update fork_gen

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... when clearing waitq. Otherwise, we risk redundantly clearing
valid waiters in future calls to `mutex_ptr`.

Note: I am not sure if this fixes [Bug #15430], and even if it
did, fork_gen is a belt-and-suspenders redundancy for [Bug #15383]
which wastes one word for every Mutex object.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66477 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
normal 2018-12-21 12:32:52 +00:00
parent 2a742d5f9b
commit fa5601e7b9
1 changed files with 16 additions and 0 deletions
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16
thread_sync.c
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@ -45,6 +45,16 @@ typedef struct rb_mutex_struct {
rb_thread_t *th;
struct rb_mutex_struct *next_mutex;
struct list_head waitq; /* protected by GVL */
/*
* FIXME: belt-and-suspenders redundancy. This field should NOT
* be necessary at all if:
* - rb_mutex_cleanup_keeping_mutexes
* - rb_mutex_abandon_keeping_mutexes
* - rb_mutex_abandon_locking_mutex
* are all correct, but I suspect one of them is buggy.
* [Bug #15383] [Bug #15430]
*/
rb_serial_t fork_gen;
} rb_mutex_t;
@ -126,6 +136,7 @@ mutex_ptr(VALUE obj)
TypedData_Get_Struct(obj, rb_mutex_t, &mutex_data_type, mutex);
/* FIXME: remove (see comment at rb_mutex_t definition) */
if (mutex->fork_gen != fork_gen) {
/* forked children can't reach into parent thread stacks */
mutex->fork_gen = fork_gen;
@ -445,7 +456,12 @@ static void
rb_mutex_cleanup_keeping_mutexes(const rb_thread_t *current_thread)
{
rb_mutex_t *mutex = current_thread->keeping_mutexes;
rb_serial_t fork_gen = current_thread->vm->fork_gen;
while (mutex) {
/* FIXME: remove (see comment at rb_mutex_t definition) */
mutex->fork_gen = fork_gen;
list_head_init(&mutex->waitq);
mutex = mutex->next_mutex;
}