simplify altstack and enable reuse with thread cache

Instead of allocating and registering the altstack in different
places, do it together to reduce code and improve readability.
When thread cache is enabled, storing altstack in rb_thread_t
is wasteful and we may reuse altstack in the same pthread.

This also lets us clearly allow use of xmalloc to allow GC to
recover from ENOMEM.

[ruby-core:85621] [Feature #14487]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63213 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 8 deletions

diff --git a/vm.c b/vm.c
index 1a57f2c6d1..dd67062ee5 100644
--- a/vm.c
+++ b/vm.c
@@ -2216,6 +2216,7 @@ ruby_vm_destruct(rb_vm_t *vm)
 	    vm->frozen_strings = 0;
 	}
 	rb_vm_gvl_destroy(vm);
+	RB_ALTSTACK_FREE(vm->main_altstack);
 	if (objspace) {
 	    rb_objspace_free(objspace);
 	}
@@ -2473,9 +2474,6 @@ thread_free(void *ptr)
 	RUBY_GC_INFO("main thread\n");
     }
     else {
-#ifdef USE_SIGALTSTACK
-	free(th->altstack);
-#endif
 	ruby_xfree(ptr);
     }
 
@@ -2535,11 +2533,6 @@ th_init(rb_thread_t *th, VALUE self)
     th->self = self;
     rb_threadptr_root_fiber_setup(th);
 
-    /* allocate thread stack */
-#ifdef USE_SIGALTSTACK
-    /* altstack of main thread is reallocated in another place */
-    th->altstack = malloc(rb_sigaltstack_size());
-#endif
     {
 	/* vm_stack_size is word number.
 	 * th->vm->default_params.thread_vm_stack_size is byte size. */