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Tidy up book keeping for `thread->keeping_mutexes`. 

When a scheduler is present, it's entirely possible for
`th->keeping_mutexes` to be updated while enumerating the waitq. Therefore
it must be fetched only during the removal operation.
This commit is contained in:
Samuel Williams 2020-11-08 16:17:04 +13:00
parent f73135233b
commit c39984ec5c
Notes: git 2020-11-08 16:41:18 +09:00 
Merged: https://github.com/ruby/ruby/pull/3743
1 changed files with 35 additions and 18 deletions
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53
thread_sync.c
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@ -192,15 +192,36 @@ rb_mutex_locked_p(VALUE self)
return mutex->fiber ? Qtrue : Qfalse;
}
static void
thread_mutex_insert(rb_thread_t *thread, rb_mutex_t *mutex) {
if (thread->keeping_mutexes) {
mutex->next_mutex = thread->keeping_mutexes;
}
thread->keeping_mutexes = mutex;
}
static void
thread_mutex_remove(rb_thread_t *thread, rb_mutex_t *mutex) {
rb_mutex_t **keeping_mutexes = &thread->keeping_mutexes;
while (*keeping_mutexes && *keeping_mutexes != mutex) {
// Move to the next mutex in the list:
keeping_mutexes = &(*keeping_mutexes)->next_mutex;
}
if (*keeping_mutexes) {
*keeping_mutexes = mutex->next_mutex;
mutex->next_mutex = NULL;
}
}
static void
mutex_locked(rb_thread_t *th, VALUE self)
{
rb_mutex_t *mutex = mutex_ptr(self);
if (th->keeping_mutexes) {
mutex->next_mutex = th->keeping_mutexes;
}
th->keeping_mutexes = mutex;
thread_mutex_insert(th, mutex);
}
/*
@ -392,18 +413,17 @@ rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t *th, rb_fiber_t *fiber)
const char *err = NULL;
if (mutex->fiber == 0) {
err = "Attempt to unlock a mutex which is not locked";
err = "Attempt to unlock a mutex which is not locked";
}
else if (mutex->fiber != fiber) {
err = "Attempt to unlock a mutex which is locked by another thread/fiber";
err = "Attempt to unlock a mutex which is locked by another thread/fiber";
}
else {
struct sync_waiter *cur = 0, *next;
rb_mutex_t **th_mutex = &th->keeping_mutexes;
struct sync_waiter *cur = 0, *next;
mutex->fiber = 0;
list_for_each_safe(&mutex->waitq, cur, next, node) {
list_del_init(&cur->node);
mutex->fiber = 0;
list_for_each_safe(&mutex->waitq, cur, next, node) {
list_del_init(&cur->node);
if (cur->th->scheduler != Qnil) {
rb_scheduler_unblock(cur->th->scheduler, cur->self, rb_fiberptr_self(cur->fiber));
@ -422,13 +442,10 @@ rb_mutex_unlock_th(rb_mutex_t *mutex, rb_thread_t *th, rb_fiber_t *fiber)
continue;
}
}
}
found:
while (*th_mutex != mutex) {
th_mutex = &(*th_mutex)->next_mutex;
}
*th_mutex = mutex->next_mutex;
mutex->next_mutex = NULL;
}
found:
thread_mutex_remove(th, mutex);
}
return err;