1 files changed, 94 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/s390/elision-trylock.c b/sysdeps/unix/sysv/linux/s390/elision-trylock.c
new file mode 100644
index 0000000000..5454b56903
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/s390/elision-trylock.c
@@ -0,0 +1,94 @@
+/* Elided pthread mutex trylock.
+   Copyright (C) 2014-2015 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 <htmintrin.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)
+{
+  __asm__ volatile (".machinemode \"zarch_nohighgprs\"\n\t"
+		    ".machine \"all\""
+		    : : : "memory");
+
+  /* Implement POSIX semantics by forbiding nesting elided trylocks.
+     Sorry.  After the abort the code is re-executed
+     non transactional and if the lock was already locked
+     return an error.  */
+  if (__builtin_tx_nesting_depth () > 0)
+    {
+      /* Note that this abort may terminate an outermost transaction that
+	 was created outside glibc.
+	 This persistently aborts the current transactions to force
+	 them to use the default lock instead of retrying transactions
+	 until their try_tbegin is zero.
+      */
+      __builtin_tabort (_HTM_FIRST_USER_ABORT_CODE | 1);
+    }
+
+  /* Only try a transaction if it's worth it.  */
+  if (*adapt_count <= 0)
+    {
+      unsigned status;
+
+      if (__builtin_expect
+	  ((status = __builtin_tbegin ((void *)0)) == _HTM_TBEGIN_STARTED, 1))
+	{
+	  if (*futex == 0)
+	    return 0;
+	  /* Lock was busy.  Fall back to normal locking.  */
+	  /* Since we are in a non-nested transaction there is no need to abort,
+	     which is expensive.  */
+	  __builtin_tend ();
+	  /* Note: Changing the adapt_count here might abort a transaction on a
+	     different cpu, but that could happen anyway when the futex is
+	     acquired, so there's no need to check the nesting depth here.  */
+	  if (aconf.skip_lock_busy > 0)
+	    *adapt_count = aconf.skip_lock_busy;
+	}
+      else
+	{
+	  if (status != _HTM_TBEGIN_TRANSIENT)
+	    {
+	      /* A persistent abort (cc 1 or 3) indicates that a retry is
+		 probably futile.  Use the normal locking now and for the
+		 next couple of calls.
+		 Be careful to avoid writing to the lock.  */
+	      if (aconf.skip_trylock_internal_abort > 0)
+		*adapt_count = aconf.skip_trylock_internal_abort;
+	    }
+	}
+      /* Could do some retries here.  */
+    }
+  else
+    {
+      /* Lost updates are possible, but harmless.  Due to races this might lead
+	 to *adapt_count becoming less than zero.  */
+      (*adapt_count)--;
+    }
+
+  return lll_trylock (*futex);
+}