thread_pthread: stop trying to deal with cancellation

We don't use pthreads cancellation ourselves and it's painful to
use correctly.  Any cancelled threads would break
vm->living_threads, GVL, thread_sync.c, autoload, etc...

So don't bother caring; because we can't stop rogue extensions
from completely breaking the VM in other ways, either.

[ruby-core:88282] [Misc #14962]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64197 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

process.c

@@ -3869,7 +3869,6 @@ has_privilege(void)
 struct child_handler_disabler_state
 {
     sigset_t sigmask;
-    int cancelstate;
 };
 
 static void
@@ -3890,13 +3889,6 @@ disable_child_handler_before_fork(struct child_handler_disabler_state *old)
 #else
 # pragma GCC warning "pthread_sigmask on fork is not available. potentially dangerous"
 #endif
-
-#ifdef PTHREAD_CANCEL_DISABLE
-    ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old->cancelstate);
-    if (ret != 0) {
-	rb_syserr_fail(ret, "pthread_setcancelstate");
-    }
-#endif
 }
 
 static void
@@ -3904,13 +3896,6 @@ disable_child_handler_fork_parent(struct child_handler_disabler_state *old)
 {
     int ret;
 
-#ifdef PTHREAD_CANCEL_DISABLE
-    ret = pthread_setcancelstate(old->cancelstate, NULL);
-    if (ret != 0) {
-	rb_syserr_fail(ret, "pthread_setcancelstate");
-    }
-#endif
-
 #ifdef HAVE_PTHREAD_SIGMASK
     ret = pthread_sigmask(SIG_SETMASK, &old->sigmask, NULL); /* not async-signal-safe */
     if (ret != 0) {

thread_pthread.c

@@ -1551,11 +1551,6 @@ mjit_worker(void *arg)
 {
     void (*worker_func)(void) = (void(*)(void))arg;
 
-#ifdef PTHREAD_CANCEL_ENABLE
-    if (pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL) != 0) {
-        fprintf(stderr, "Cannot enable cancellation in MJIT worker\n");
-    }
-#endif
 #ifdef SET_CURRENT_THREAD_NAME
     SET_CURRENT_THREAD_NAME("ruby-mjitworker"); /* 16 byte including NUL */
 #endif