Poor-man's global scope switch support: just busy-waits.
---
 elf/dl-support.c                  |    1 +
 sysdeps/generic/ldsodefs.h        |    1 +
 sysdeps/mach/hurd/sysdep-cancel.h |    9 +++++++++
 sysdeps/mach/hurd/tls.h           |   13 +++++++++++++
 4 files changed, 24 insertions(+)

--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -141,6 +141,7 @@
 /* Function in libpthread to wait for termination of lookups.  */
 void (*_dl_wait_lookup_done) (void);
 
+int volatile _dl_thread_gscope_count;
 struct dl_scope_free_list *_dl_scope_free_list;
 
 #ifdef NEED_DL_SYSINFO
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -493,6 +493,7 @@
     size_t count;
     void *list[50];
   } *_dl_scope_free_list;
+  EXTERN volatile int _dl_thread_gscope_count;
 #ifdef SHARED
 };
 # define __rtld_global_attribute__
--- a/sysdeps/mach/hurd/tls.h
+++ b/sysdeps/mach/hurd/tls.h
@@ -74,5 +74,18 @@
 
 #endif /* HAVE_TLS_SUPPORT */
 
+#ifndef __ASSEMBLER__
+#include <mach/mach_traps.h>
+#include <atomic.h>
+/* Temporary poor-man's global scope switch support: just busy-waits */
+#define THREAD_GSCOPE_SET_FLAG() \
+	asm volatile ("lock incl %0":"=m"(GL(dl_thread_gscope_count)))
+#define THREAD_GSCOPE_RESET_FLAG() \
+	asm volatile ("lock decl %0":"=m"(GL(dl_thread_gscope_count)))
+#define THREAD_GSCOPE_WAIT() \
+  while (GL(dl_thread_gscope_count)) { \
+    __swtch_pri (0); \
+  }
+#endif
 
 #endif /* tls.h */
--- /dev/null
+++ b/sysdeps/mach/hurd/sysdep-cancel.h
@@ -0,0 +1,9 @@
+#include <sysdep.h>
+
+/* Always multi-thread (since there's at least the sig handler), but no
+   handling enabled.  */
+#define SINGLE_THREAD_P (0)
+#define RTLD_SINGLE_THREAD_P (0)
+#define LIBC_CANCEL_ASYNC()	0 /* Just a dummy value.  */
+#define LIBC_CANCEL_RESET(val)	((void)(val)) /* Nothing, but evaluate it.  */
+#define LIBC_CANCEL_HANDLED()	/* Nothing.  */