[RFC PATCH glibc 3/3] XXX: Reimplement gscope

[Sergey Bugaev]

This moves the Hurd gsope implementation to be more like the Linux
one.
---
 sysdeps/generic/ldsodefs.h          |  2 --
 sysdeps/htl/dl-thread_gscope_wait.c | 36 +++++++++++++++++++++++++++++
 sysdeps/mach/hurd/i386/tls.h        | 22 ++++++++++++++++++
 sysdeps/mach/hurd/tls.h             | 20 ----------------
 4 files changed, 58 insertions(+), 22 deletions(-)
 create mode 100644 sysdeps/htl/dl-thread_gscope_wait.c

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 4604d00b..af16162f 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -1324,10 +1324,8 @@ link_map_audit_state (struct link_map *l, size_t index)
 }
 #endif /* SHARED */
 
-#if THREAD_GSCOPE_IN_TCB
 void __thread_gscope_wait (void) attribute_hidden;
 # define THREAD_GSCOPE_WAIT() __thread_gscope_wait ()
-#endif
 
 __END_DECLS
 
diff --git a/sysdeps/htl/dl-thread_gscope_wait.c 
b/sysdeps/htl/dl-thread_gscope_wait.c
new file mode 100644
index 00000000..66b75194
--- /dev/null
+++ b/sysdeps/htl/dl-thread_gscope_wait.c
@@ -0,0 +1,36 @@
+/* TODO: copyright heading */
+
+#include <ldsodefs.h>
+#include <pthread.h>
+#include <htl/pt-internal.h>
+
+void
+__thread_gscope_wait (void)
+{
+  size_t i;
+  struct __pthread *t;
+  int *flag_ptr;
+
+  lll_lock (GL (dl_pthread_threads_lock), 0);
+
+  for (i = 0; i < GL (dl_pthread_num_threads); ++i)
+    {
+      t = GL (dl_pthread_threads[i]);
+      if (t == NULL)
+        continue;
+
+      flag_ptr = &t->tcb->gscope_flag;
+ again:
+      if (atomic_load_acquire (flag_ptr) == THREAD_GSCOPE_FLAG_UNUSED)
+        continue;
+
+      if (atomic_compare_and_exchange_bool_acq (flag_ptr,
+                                                THREAD_GSCOPE_FLAG_WAIT,
+                                                THREAD_GSCOPE_FLAG_USED))
+        goto again;
+
+      lll_wait (flag_ptr, THREAD_GSCOPE_FLAG_WAIT, 0);
+    }
+
+  lll_unlock (GL (dl_pthread_threads_lock), 0);
+}
diff --git a/sysdeps/mach/hurd/i386/tls.h b/sysdeps/mach/hurd/i386/tls.h
index 057b2613..0ca4e641 100644
--- a/sysdeps/mach/hurd/i386/tls.h
+++ b/sysdeps/mach/hurd/i386/tls.h
@@ -369,6 +369,28 @@ _hurd_tls_new (thread_t child, struct i386_thread_state 
*state, tcbhead_t *tcb)
   return err;
 }
 
+/* Global scope switch support.  */
+#define THREAD_GSCOPE_LINK_MAP      0
+
+# define THREAD_GSCOPE_FLAG_UNUSED 0
+# define THREAD_GSCOPE_FLAG_USED   1
+# define THREAD_GSCOPE_FLAG_WAIT   2
+
+#define THREAD_GSCOPE_SET_FLAG() \
+  THREAD_SETMEM (THREAD_SELF, gscope_flag, THREAD_GSCOPE_FLAG_USED)
+
+#define THREAD_GSCOPE_RESET_FLAG() \
+  ({                                                           \
+    int __flag;                                                        \
+    asm volatile ("xchgl %0, %%gs:%P1"                         \
+                  : "=r" (__flag)                              \
+                  : "i" (offsetof (tcbhead_t, gscope_flag)),   \
+                    "0" (THREAD_GSCOPE_FLAG_UNUSED));          \
+    if (__flag == THREAD_GSCOPE_FLAG_WAIT)                     \
+      lll_wake (THREAD_SELF->gscope_flag, GSYNC_BROADCAST);    \
+  })
+
+
 #endif /* !__ASSEMBLER__ */
 
 #endif /* i386/tls.h */
diff --git a/sysdeps/mach/hurd/tls.h b/sysdeps/mach/hurd/tls.h
index 8cbf22aa..8e66d5ff 100644
--- a/sysdeps/mach/hurd/tls.h
+++ b/sysdeps/mach/hurd/tls.h
@@ -52,26 +52,6 @@
 # define GET_DTV(descr) \
   (((tcbhead_t *) (descr))->dtv)
 
-/* Global scope switch support.  */
-#define THREAD_GSCOPE_LINK_MAP    0
-#define THREAD_GSCOPE_GLOBAL
-#define THREAD_GSCOPE_SET_FLAG() \
-  atomic_exchange_and_add_acq (&GL(dl_thread_gscope_count), 1)
-#define THREAD_GSCOPE_RESET_FLAG() \
-  do                                                                         \
-    if (atomic_exchange_and_add_rel (&GL(dl_thread_gscope_count), -1) == 1)   \
-      lll_wake (GL(dl_thread_gscope_count), 0);                                
      \
-  while (0)
-#define THREAD_GSCOPE_WAIT() \
-  do                                                                         \
-    {                                                                        \
-      int count;                                                             \
-      atomic_write_barrier ();                                               \
-      while ((count = GL(dl_thread_gscope_count)))                           \
-        lll_wait (GL(dl_thread_gscope_count), count, 0);                     \
-    }                                                                        \
-  while (0)
-
 #endif /* !ASSEMBLER */
 
 
-- 
2.31.1