1 files changed, 75 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/unix/sysv/linux/x86/elision-trylock.c b/REORG.TODO/sysdeps/unix/sysv/linux/x86/elision-trylock.c
new file mode 100644
index 0000000000..c19293bf7a
--- /dev/null
+++ b/REORG.TODO/sysdeps/unix/sysv/linux/x86/elision-trylock.c
@@ -0,0 +1,75 @@
+/* elision-trylock.c: Lock eliding trylock for pthreads.
+   Copyright (C) 2013-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <pthread.h>
+#include <pthreadP.h>
+#include <lowlevellock.h>
+#include "hle.h"
+#include <elision-conf.h>
+
+#define aconf __elision_aconf
+
+/* Try to elide a futex trylock.  FUTEX is the futex variable.  ADAPT_COUNT is
+   the adaptation counter in the mutex.  */
+
+int
+__lll_trylock_elision (int *futex, short *adapt_count)
+{
+  /* Implement POSIX semantics by forbiding nesting
+     trylock.  Sorry.  After the abort the code is re-executed
+     non transactional and if the lock was already locked
+     return an error.  */
+  _xabort (_ABORT_NESTED_TRYLOCK);
+
+  /* Only try a transaction if it's worth it.  See __lll_lock_elision for
+     why we need atomic accesses.  Relaxed MO is sufficient because this is
+     just a hint.  */
+  if (atomic_load_relaxed (adapt_count) <= 0)
+    {
+      unsigned status;
+
+      if ((status = _xbegin()) == _XBEGIN_STARTED)
+	{
+	  if (*futex == 0)
+	    return 0;
+
+	  /* Lock was busy.  Fall back to normal locking.
+	     Could also _xend here but xabort with 0xff code
+	     is more visible in the profiler.  */
+	  _xabort (_ABORT_LOCK_BUSY);
+	}
+
+      if (!(status & _XABORT_RETRY))
+        {
+          /* Internal abort.  No chance for retry.  For future
+             locks don't try speculation for some time.  See above for MO.  */
+          if (atomic_load_relaxed (adapt_count)
+              != aconf.skip_lock_internal_abort)
+            atomic_store_relaxed (adapt_count, aconf.skip_lock_internal_abort);
+        }
+      /* Could do some retries here.  */
+    }
+  else
+    {
+      /* Lost updates are possible but harmless (see above).  */
+      atomic_store_relaxed (adapt_count,
+	  atomic_load_relaxed (adapt_count) - 1);
+    }
+
+  return lll_trylock (*futex);
+}