1 files changed, 57 insertions, 0 deletions
diff --git a/libiohelp/get_conch.c b/libiohelp/get_conch.c
new file mode 100644
index 00000000..64d347ab
--- /dev/null
+++ b/libiohelp/get_conch.c
@@ -0,0 +1,57 @@
+/* 
+   Copyright (C) 1993, 1994, 1996 Free Software Foundation
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include "iohelp.h"
+
+/* The conch must be locked when calling this routine. */
+/* Remove any current holder of conch C. */
+void
+iohelp_get_conch (struct conch *c)
+{
+  struct shared_io *user_sh;
+  
+ again:
+  user_sh = c->holder_shared_page;
+  
+  if (user_sh)
+    {
+      spin_lock (&user_sh->lock);
+      switch (user_sh->conch_status)
+	{
+	case USER_HAS_CONCH:
+	  user_sh->conch_status = USER_RELEASE_CONCH;
+	  /* fall through ... */
+	case USER_RELEASE_CONCH:
+	  spin_unlock (&user_sh->lock);
+	  condition_wait (&c->wait, c->lock);
+	  /* Anything can have happened */
+	  goto again;
+	  
+	case USER_COULD_HAVE_CONCH:
+	  user_sh->conch_status = USER_HAS_NOT_CONCH;
+	  spin_unlock (&user_sh->lock);
+	  iohelp_fetch_shared_data (c->holder);
+	  break;
+	  
+	case USER_HAS_NOT_CONCH:
+	  spin_unlock (&user_sh->lock);
+	  break;
+	}
+    }
+  c->holder = 0;
+  c->holder_shared_page = 0;
+}