7 files changed, 96 insertions, 6 deletions
diff --git a/nptl/Makefile b/nptl/Makefile
index 98b0aa01c7..34ae830276 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -145,7 +145,7 @@ libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
 		      mtx_destroy mtx_init mtx_lock mtx_timedlock \
 		      mtx_trylock mtx_unlock call_once cnd_broadcast \
 		      cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait \
-		      tss_create tss_delete tss_get tss_set
+		      tss_create tss_delete tss_get tss_set pthread_mutex_conf
 #		      pthread_setuid pthread_seteuid pthread_setreuid \
 #		      pthread_setresuid \
 #		      pthread_setgid pthread_setegid pthread_setregid \
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 907411d5bc..20ff3fd559 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -38,6 +38,7 @@
 #include <kernel-features.h>
 #include <libc-pointer-arith.h>
 #include <pthread-pids.h>
+#include <pthread_mutex_conf.h>
 
 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
 /* Pointer to the corresponding variable in libc.  */
@@ -431,6 +432,10 @@ __pthread_initialize_minimal_internal (void)
 
   /* Determine whether the machine is SMP or not.  */
   __is_smp = is_smp_system ();
+
+#if HAVE_TUNABLES
+  __pthread_tunables_init ();
+#endif
 }
 strong_alias (__pthread_initialize_minimal_internal,
 	      __pthread_initialize_minimal)
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 19efe1e35f..7f16ba9800 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -33,6 +33,7 @@
 #include <kernel-features.h>
 #include <errno.h>
 #include <internal-signals.h>
+#include "pthread_mutex_conf.h"
 
 
 /* Atomic operations on TLS memory.  */
@@ -47,10 +48,14 @@
 #endif
 
 
-/* Adaptive mutex definitions.  */
-#ifndef MAX_ADAPTIVE_COUNT
-# define MAX_ADAPTIVE_COUNT 100
+static inline short max_adaptive_count (void)
+{
+#if HAVE_TUNABLES
+  return __mutex_aconf.spin_count;
+#else
+  return DEFAULT_ADAPTIVE_COUNT;
 #endif
+}
 
 
 /* Magic cookie representing robust mutex with dead owner.  */
diff --git a/nptl/pthread_mutex_conf.c b/nptl/pthread_mutex_conf.c
new file mode 100644
index 0000000000..545e05b360
--- /dev/null
+++ b/nptl/pthread_mutex_conf.c
@@ -0,0 +1,46 @@
+/* Pthread mutex tunable parameters.
+   Copyright (C) 2018 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/>.  */
+
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE pthread
+#include <pthread_mutex_conf.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <unistd.h>  /* Get STDOUT_FILENO for _dl_printf.  */
+#include <elf/dl-tunables.h>
+
+struct mutex_config __mutex_aconf =
+{
+  /* The maximum number of times a thread should spin on the lock before
+  calling into kernel to block.  */
+  .spin_count = DEFAULT_ADAPTIVE_COUNT,
+};
+
+static void
+TUNABLE_CALLBACK (set_mutex_spin_count) (tunable_val_t *valp)
+{
+  __mutex_aconf.spin_count = (int32_t) (valp)->numval;
+}
+
+void
+__pthread_tunables_init (void)
+{
+  TUNABLE_GET (mutex_spin_count, int32_t,
+               TUNABLE_CALLBACK (set_mutex_spin_count));
+}
+#endif
diff --git a/nptl/pthread_mutex_conf.h b/nptl/pthread_mutex_conf.h
new file mode 100644
index 0000000000..514d1052c0
--- /dev/null
+++ b/nptl/pthread_mutex_conf.h
@@ -0,0 +1,34 @@
+/* Pthread mutex tunable parameters.
+   Copyright (C) 2018 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/>.  */
+#ifndef _PTHREAD_MUTEX_CONF_H
+#define _PTHREAD_MUTEX_CONF_H 1
+
+#include <adaptive_spin_count.h>
+
+#if HAVE_TUNABLES
+struct mutex_config
+{
+  int spin_count;
+};
+
+extern struct mutex_config __mutex_aconf attribute_hidden;
+
+extern void __pthread_tunables_init (void) attribute_hidden;
+#endif
+
+#endif
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 29cc143e6c..474b4df765 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -126,7 +126,7 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
       if (LLL_MUTEX_TRYLOCK (mutex) != 0)
 	{
 	  int cnt = 0;
-	  int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
+	  int max_cnt = MIN (max_adaptive_count (),
 			     mutex->__data.__spins * 2 + 10);
 	  do
 	    {
diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index 888c12fe28..453b824030 100644
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -118,7 +118,7 @@ __pthread_mutex_timedlock (pthread_mutex_t *mutex,
       if (lll_trylock (mutex->__data.__lock) != 0)
 	{
 	  int cnt = 0;
-	  int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
+	  int max_cnt = MIN (max_adaptive_count (),
 			     mutex->__data.__spins * 2 + 10);
 	  do
 	    {