Revert "Pass down "stack start" variables from closer to the top of the stack"

This reverts commit 4ba8f0dc993953d3ddda6328e3ef17a2fc2cbde5.

1 files changed, 5 insertions, 16 deletions

diff --git a/thread_pthread.c b/thread_pthread.c
index a6a6c9d127..6d2f55a957 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1964,7 +1964,7 @@ reserve_stack(volatile char *limit, size_t size)
 
 #undef ruby_init_stack
 void
-ruby_init_stack(volatile void *addr)
+ruby_init_stack(volatile VALUE *addr)
 {
     native_main_thread.id = pthread_self();
 
@@ -2049,7 +2049,7 @@ ruby_init_stack(volatile void *addr)
     {int err = (expr); if (err) {rb_bug_errno(#expr, err);}}
 
 static int
-native_thread_init_stack(rb_thread_t *th, void *local_in_parent_frame)
+native_thread_init_stack(rb_thread_t *th)
 {
     rb_nativethread_id_t curr = pthread_self();
 
@@ -2064,8 +2064,8 @@ native_thread_init_stack(rb_thread_t *th, void *local_in_parent_frame)
             size_t size;
 
             if (get_stack(&start, &size) == 0) {
-                uintptr_t diff = (uintptr_t)start - (uintptr_t)local_in_parent_frame;
-                th->ec->machine.stack_start = (uintptr_t)local_in_parent_frame;
+                uintptr_t diff = (uintptr_t)start - (uintptr_t)&curr;
+                th->ec->machine.stack_start = (VALUE *)&curr;
                 th->ec->machine.stack_maxsize = size - diff;
             }
         }
@@ -2185,19 +2185,8 @@ native_thread_create_dedicated(rb_thread_t *th)
 static void
 call_thread_start_func_2(rb_thread_t *th)
 {
-    /* Capture the address of a local in this stack frame to mark the beginning of the
-       machine stack for this thread. This is required even if we can tell the real
-       stack beginning from the pthread API in native_thread_init_stack, because
-       glibc stores some of its own data on the stack before calling into user code
-       on a new thread, and replacing that data on fiber-switch would break it (see
-       bug #13887) */
-    VALUE stack_start = 0;
-    VALUE *stack_start_addr = &stack_start;
-    native_thread_init_stack(th, stack_start_addr);
+    native_thread_init_stack(th);
     thread_start_func_2(th, th->ec->machine.stack_start);
-
-    /* Ensure that stack_start really was spilled to the stack */
-    RB_GC_GUARD(stack_start)
 }
 
 static void *