This reverts commit c474846c42.
In addition, `s->loop` is also checked before dispatching a source.
The destroy list is needed in the presence of threads. The
issue is that a source may be destroyed between `epoll_wait()`
returning and thread loop lock being acquired. If this
source is active, then a use-after-free will be triggered
when the thread loop acquires the lock and starts dispatching
the sources.
thread 1 thread 2
---------- ----------
loop_iterate
spa_loop_control_hook_before
// release lock
pw_thread_loop_lock
spa_system_pollfd_wait
// assume it returns with source A
pw_loop_destroy_source(..., A)
// frees storage of A
pw_thread_loop_unlock
spa_loop_control_hook_after
// acquire the lock
for (...) {
struct spa_source *s = ep[i].data;
s->rmask = ep[i].events;
// use-after-free if `s` refers to
// the previously freed `A`
Fixes#2147
16f63a3c8f