Patchwork [v3,1/2] Mutex: Accelerate lock acquisition by queuing spinner

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Submitter Kemi Wang
Date Jan. 14, 2019, 5:01 a.m.
Message ID <1547442104-24364-1-git-send-email-kemi.wang@intel.com>
Download mbox | patch
Permalink /patch/31050/
State New
Headers show

Comments

Kemi Wang - Jan. 14, 2019, 5:01 a.m.
Adaptive mutex indicates the semantic of spinning for a while before
calling into the kernel to block. Thus, the lock of adaptive mutex could be
acquired via immediate getting, spinning getting or waking up.

Currently, the spin-waiting algorithm of adaptive mutex is for each
processor to repeatedly execute an test_and_set instruction until either
the maximum spin count is reached or the  lock is acquired. However, the
lock performance via spinning getting will degrade significantly as the
number of spinning processors increases. Two factors at least cause this
degradation[1]. First, in order to release the lock, the lock holder has to
contend with spinning processors for exclusive access of lock cache line.
(E.g. "lock; decl 0%" of lll_unlock() in
sysdeps/unix/sysv/linux/x86_64/lowlevellock.h for pthread_mutex_unlock()).
For most multiprocessor architectures, it has to wait behind those
test_and_set instructions from spinning processors.
Furthermore, on these invalidation-based cache coherency system,
test_and_set instruction will trigger a "read-for-ownership" request for
exclusive access to the lock cache line, it will potentially slow the
access of other locations(shares the cache line with the lock at least) by
the lock holder.

In this patch, we propose another spin-waiting algorithm to accelerate
lock acquisition by queuing spinners based-on MCS[2] lock. With MCS
algorithm, only the header of queue is allowed to spin on the mutex lock,
others spin on locally-accessible flag variables. Thus, the previous
negative factors are eliminated.

The implementation of this MCS-based spin-waiting algorithm requires an
additional pointer to hold the tail of queue. To keep the size of mutex
data structure constant and maintain the user space ABI unchanged, the
__list field which is originally for implementing robust futex will be
reused. Therefore, we propose a new type mutex with GNU extension
PTHREAD_MUTEX_QUEUESPINNER_NP in this patch.

Pass the ABI compatibility test by running "make check-abi"

The benchmark is available at branch mutex_testing in
https://github.com/kemicoco/tst-spinlock.git.
The tunable pthread.mutex_spin_count is set to 10000 which is big enough in
our testing for fair comparison.

The first test case emulates a practical workload with mathematical
calculation.
The second test case provided by our customer emulates the lock contention
in a distributed file system.

Each workload runs with multiple threads in parallel, each workload does
a) Acquire the lock;
b) Do some work in critical section;
c) Unlock
d) Wait a random time (0~3000 TSCs)
in a loop until 5 seconds, and obtain the total iterations.

Testing on 2s-Skylake platform (112 cores with 62G RAM, HT=on).
TC1: Hashwork
Thread num      adaptive mutex          mcs mutex
	1               7297792             7298755 (+0.01%)
	2               9332105             9752901 (+4.51%)
	3               10428251            11029771 (+5.7%)
	4               10572596            11203997 (+5.9%)
	5               10496815            11008433 (+4.8%)
	6               10292946            10569467 (+2.6%)
	7               9861111             10153538 (+2.97%)
	14              5845303             9756283  (+66.91%)
	28              4299209             8985135  (+109.0%)
	56              3298821             5747645  (+74.23%)
	112             2941309             5629700  (+91.4%)
	448             2821056             3716799  (+31.75%)

TC2: Test_and_set instruction on shared variables
Thread num      adaptive mutex          mcs mutex
	1               7748765             7751963 (+0.04%)
	2               8521596             9251649 (+8.57%)
	3               9594653             9890211 (+3.08%)
	4               9934361             9800205 (-1.35%)
	5               8146007             9597982 (+17.82%)
	6               6896436             9367882 (+35.84%)
	7               5943880             9159893 (+54.11%)
	14              4194305             8623029 (+105.59%)
	28              3374218             7818631 (+131.72%)
	56              2533912             4836622 (+90.88%)
	112             2541950             4850938 (+90.84%)
	448             2507000             5345149 (+113.21%)

Test result on workstation(16 cores with 32G RAM, HT=on)
TC1: Hashwork
Thread num      adaptive mutex          mcs mutex
	1               11419169            11430369 (+0.1%)
	2               15364452            15873667 (+3.31%)
	3               17234014            17547329 (+1.82%)
	4               17711736            17613548 (-0.55%)
	5               16583392            17626707 (+6.29%)
	6               14855586            17305468 (+16.49%)
	7               12948851            17130807 (+32.3%)
	14              8698172             15322237 (+76.15%)
	16              8123930             14937645 (+83.87%)
	64              7946006             5685132 (-28.45%)

TC2: Test_and_set instruction on shared variables
Thread num      adaptive mutex          mcs mutex
	1               12535156            12595629 (+0.48%)
	2               15665576            15929652 (+1.69%)
	3               17469331            16881225 (-3.37%)
	4               14833035            15777572 (+6.37%)
	5               12376033            15256528 (+23.27%)
	6               10568899            14693661 (+39.03%)
	7               9657775             14486039 (+49.99%)
	14              8015061             14112508 (+76.07%)
	16              7641725             13935473 (+82.36%)
	64              7571112             7735482 (+2.17%)

Potential issues:
a) As the preemption can't be disabled at userland during spinning, MCS
style lock potentially has the risk to collapse lock performance when CPUs
are heavily oversubscribed. But generally, MCS-based spin-waiting algorithm
performs much better than the existed one. We may consider to mitigate this
issue by using a cancellable MCS to prevent unnecessary active waiting in
future.

Reference:
[1]"The performance of spin lock alternatives for shared-memory
multiprocessors"
https://www.cc.gatech.edu/classes/AY2009/cs4210_fall/papers/anderson-spinlock.pdf.
[2]"Algorithms for scalable synchronization on shared-memory
multiprocessors"
http://www.cs.rochester.edu/~scott/papers/1991_TOCS_synch.pdf

    * NEWS: New entry.
    * nptl/Makefile (libpthread-routines): Add mcs_lock.
    * nptl/mcs_lock.c: New file
    * nptl/mcs_lock.h: New file
    * nptl/allocatestack.c (__data.__list): Convert to __data.__list.__list_t
    * nptl/descr.h (__data.__list): Likewise
    * nptl/nptl-init.c (__data.__list): Likewise
    * nptl/pthreadP.h: Extend mutex type mask
    * nptl/pthread_mutex_init.c: Add robust futex checking
    * nptl/pthread_mutex_lock.c: Implement a new mutex prototype
    * nptl/pthread_mutex_timedlock.c: Likewise
    * nptl/pthread_mutex_trylock.c: Likewise
    * nptl/pthread_mutex_unlock.c: Likewise
    * nptl/pthread_mutexattr_settype.c: Set a new mutex attribution
    * sysdeps/nptl/bits/thread-shared-types.h: Redefine
      struct __pthread_internal_list and define mcs_lock_t
    * sysdeps/nptl/pthread.h: Add a new mutex type
    * sysdeps/unix/sysv/linux/hppa/pthread.h: Likewise

May todo list:
  a) Add mutex performance test cases at benchtests
  b) Update mutex description at nptl/thread.texi
  c) Update nptl/printers.py

V2->V3 (Most for addressing Siddhesh Poyarekar's comments):
  a) Add changelog entry
  b) Add detailed description on synchronization usage in mcs_lock.c
  c) Correct formatting on mcs_lock ()/mcs_unlock () definition
  d) Only keep necessary info in NEWS
  e) Remove superfluous barrier in mcs_lock.c
  f) Remove one line superfluous code (node.locked = 1)
  g) Use atomic_load_acquire in mcs_lock () instead of atomic_load_relaxed to
  synchronizes-with atomic_store_release in mcs_unlock
  h) Add PI/PP support for this new type mutex with GUN extension
  PTHREAD_MUTEX_QUEUESPINNER_NP

V1->V2:
  a) Add one line description before copyright in new files
  b) Add one entry to introduce this new type of mutex with GNU
  PTHREAD_MUTEX_QUEUESPINNER_NP extension in NEWS

Signed-off-by: Kemi Wang <kemi.wang@intel.com>
---
 NEWS                                    |  3 ++
 nptl/Makefile                           |  3 +-
 nptl/allocatestack.c                    |  2 +-
 nptl/descr.h                            | 26 +++++-----
 nptl/mcs_lock.c                         | 87 +++++++++++++++++++++++++++++++++
 nptl/mcs_lock.h                         | 23 +++++++++
 nptl/nptl-init.c                        |  2 +-
 nptl/pthreadP.h                         |  6 ++-
 nptl/pthread_mutex_init.c               |  5 ++
 nptl/pthread_mutex_lock.c               | 36 +++++++++++++-
 nptl/pthread_mutex_timedlock.c          | 33 +++++++++++--
 nptl/pthread_mutex_trylock.c            |  7 ++-
 nptl/pthread_mutex_unlock.c             |  9 +++-
 nptl/pthread_mutexattr_settype.c        |  2 +-
 sysdeps/nptl/bits/thread-shared-types.h | 21 ++++++--
 sysdeps/nptl/pthread.h                  | 15 ++++--
 sysdeps/unix/sysv/linux/hppa/pthread.h  |  4 ++
 17 files changed, 247 insertions(+), 37 deletions(-)
 create mode 100644 nptl/mcs_lock.c
 create mode 100644 nptl/mcs_lock.h
Joseph Myers - Jan. 14, 2019, 6:08 p.m.
On Mon, 14 Jan 2019, Kemi Wang wrote:

> +/* MCS-style lock for queuing spinners
> +   Copyright (C) 2018 Free Software Foundation, Inc.

Any patch submission now including new files needs to include 2019 in 
their copyright dates.
Kemi Wang - Jan. 15, 2019, 1:46 a.m.
On 2019/1/15 上午2:08, Joseph Myers wrote:
> On Mon, 14 Jan 2019, Kemi Wang wrote:
> 
>> +/* MCS-style lock for queuing spinners
>> +   Copyright (C) 2018 Free Software Foundation, Inc.
> 
> Any patch submission now including new files needs to include 2019 in 
> their copyright dates.
> 

sure.

Patch

diff --git a/NEWS b/NEWS
index ae80818..0521b56 100644
--- a/NEWS
+++ b/NEWS
@@ -46,6 +46,9 @@  Major new features:
   incosistent mutex state after fork call in multithread environment.
   In both popen and system there is no direct access to user-defined mutexes.
 
+* The mutex with PTHREAD_MUTEX_QUEUESPINNER_NP GNU extension has been added,
+  which accelerates lock acquisition by queuing spinners.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * The glibc.tune tunable namespace has been renamed to glibc.cpu and the
diff --git a/nptl/Makefile b/nptl/Makefile
index 34ae830..0de8df3 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -145,7 +145,8 @@  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 pthread_mutex_conf
+		      tss_create tss_delete tss_get tss_set pthread_mutex_conf \
+		      mcs_lock
 #		      pthread_setuid pthread_seteuid pthread_setreuid \
 #		      pthread_setresuid \
 #		      pthread_setgid pthread_setegid pthread_setregid \
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 04e3f08..9f47129 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -749,7 +749,7 @@  allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
      might have happened in the kernel.  */
   pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
 				  - offsetof (pthread_mutex_t,
-					      __data.__list.__next));
+					      __data.__list.__list_t.__next));
   pd->robust_head.list_op_pending = NULL;
 #if __PTHREAD_MUTEX_HAVE_PREV
   pd->robust_prev = &pd->robust_head;
diff --git a/nptl/descr.h b/nptl/descr.h
index 9c01e1b..e47c7cf 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -184,38 +184,38 @@  struct pthread
      FIXME We should use relaxed MO atomic operations here and signal fences
      because this kind of concurrency is similar to synchronizing with a
      signal handler.  */
-# define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __next))
+# define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __list_t.__next))
 
 # define ENQUEUE_MUTEX_BOTH(mutex, val)					      \
   do {									      \
     __pthread_list_t *next = (__pthread_list_t *)			      \
       ((((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_head.list)) & ~1ul)   \
        - QUEUE_PTR_ADJUST);						      \
-    next->__prev = (void *) &mutex->__data.__list.__next;		      \
-    mutex->__data.__list.__next = THREAD_GETMEM (THREAD_SELF,		      \
+    next->__list_t.__prev = (void *) &mutex->__data.__list.__list_t.__next;		      \
+    mutex->__data.__list.__list_t.__next = THREAD_GETMEM (THREAD_SELF,		      \
 						 robust_head.list);	      \
-    mutex->__data.__list.__prev = (void *) &THREAD_SELF->robust_head;	      \
+    mutex->__data.__list.__list_t.__prev = (void *) &THREAD_SELF->robust_head;	      \
     /* Ensure that the new list entry is ready before we insert it.  */	      \
     __asm ("" ::: "memory");						      \
     THREAD_SETMEM (THREAD_SELF, robust_head.list,			      \
-		   (void *) (((uintptr_t) &mutex->__data.__list.__next)	      \
+		   (void *) (((uintptr_t) &mutex->__data.__list.__list_t.__next)	      \
 			     | val));					      \
   } while (0)
 # define DEQUEUE_MUTEX(mutex) \
   do {									      \
     __pthread_list_t *next = (__pthread_list_t *)			      \
-      ((char *) (((uintptr_t) mutex->__data.__list.__next) & ~1ul)	      \
+      ((char *) (((uintptr_t) mutex->__data.__list.__list_t.__next) & ~1ul)	      \
        - QUEUE_PTR_ADJUST);						      \
-    next->__prev = mutex->__data.__list.__prev;				      \
+    next->__list_t.__prev = mutex->__data.__list.__list_t.__prev;				      \
     __pthread_list_t *prev = (__pthread_list_t *)			      \
-      ((char *) (((uintptr_t) mutex->__data.__list.__prev) & ~1ul)	      \
+      ((char *) (((uintptr_t) mutex->__data.__list.__list_t.__prev) & ~1ul)	      \
        - QUEUE_PTR_ADJUST);						      \
-    prev->__next = mutex->__data.__list.__next;				      \
+    prev->__list_t.__next = mutex->__data.__list.__list_t.__next;			\
     /* Ensure that we remove the entry from the list before we change the     \
        __next pointer of the entry, which is read by the kernel.  */	      \
     __asm ("" ::: "memory");						      \
-    mutex->__data.__list.__prev = NULL;					      \
-    mutex->__data.__list.__next = NULL;					      \
+    mutex->__data.__list.__list_t.__prev = NULL;					      \
+    mutex->__data.__list.__list_t.__next = NULL;					      \
   } while (0)
 #else
   union
@@ -226,7 +226,7 @@  struct pthread
 
 # define ENQUEUE_MUTEX_BOTH(mutex, val)					      \
   do {									      \
-    mutex->__data.__list.__next						      \
+    mutex->__data.__list.__list_t.__next						      \
       = THREAD_GETMEM (THREAD_SELF, robust_list.__next);		      \
     /* Ensure that the new list entry is ready before we insert it.  */	      \
     __asm ("" ::: "memory");						      \
@@ -253,7 +253,7 @@  struct pthread
 	/* Ensure that we remove the entry from the list before we change the \
 	   __next pointer of the entry, which is read by the kernel.  */      \
 	    __asm ("" ::: "memory");					      \
-	mutex->__data.__list.__next = NULL;				      \
+	mutex->__data.__list.__list_t.__next = NULL;				      \
       }									      \
   } while (0)
 #endif
diff --git a/nptl/mcs_lock.c b/nptl/mcs_lock.c
new file mode 100644
index 0000000..835fbce
--- /dev/null
+++ b/nptl/mcs_lock.c
@@ -0,0 +1,87 @@ 
+/* MCS-style lock for queuing spinners
+   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/>.  */
+
+#include "pthreadP.h"
+#include <atomic.h>
+
+static __thread mcs_lock_t node = {
+  NULL,
+  0,
+};
+
+void
+mcs_lock (mcs_lock_t **lock)
+{
+  mcs_lock_t *prev;
+
+  /* Initialize node.  */
+  node.next = NULL;
+  node.locked = 0;
+
+  /* Move the tail pointer of the queue (lock) to point to current TLS node
+   * atomically, and return the previous tail pointer of the queue. This
+   * atomic_exchange_acquire ensures the strict FIFO order in the queue when
+   * multiple spinners compete to enqueue.  */
+  prev = atomic_exchange_acquire(lock, &node);
+
+  /* No active spinner, mcs lock is acquired immediately.  */
+  if (prev == NULL)
+    return;
+
+  /* Add current spinner into the queue.  */
+    atomic_store_relaxed (&prev->next, &node);
+  /* Waiting until mcs lock holder is passed down from the previous spinner.
+   * Using atomic_load_acquire to synchronizes-with the atomic_store_release
+   * in mcs_unlock, and ensure that prior critical sections happen-before
+   * this critical section.  */
+  while (!atomic_load_acquire (&node.locked))
+    atomic_spin_nop ();
+}
+
+void
+mcs_unlock (mcs_lock_t **lock)
+{
+  mcs_lock_t *next = node.next;
+
+  /* If the next pointer is not NULL, it indicates that we are not the last
+   * spinner in the queue, thus we have to pass down mcs lock holder to the
+   * next spinner before exiting. If the next pointer is NULL, there are
+   * two possible cases, a) we are the last one in the queue, thus we reset
+   * the tail pointer of the queue to NULL, b) the tail pointer of the
+   * queue has moved to point to a new spinner, but this new spinner has
+   * not been added to the queue. thus we have to wait until it is added to
+   * the queue.  */
+  if (next == NULL)
+    {
+      /* a) Use a CAS instruction to set lock to NULL if the tail pointer
+       * points to current node.  */
+      if (atomic_compare_and_exchange_val_acq(lock, NULL, &node) == &node)
+        return;
+
+      /* b) When we reaches here, we hit case b) aforementioned because
+       * there is a time window between updating the tail pointer of queue
+       * and adding a new spinner to the queue in mcs_lock (). Using
+       * relax MO until we observe the new spinner is added to the queue.  */
+      while (! (next = atomic_load_relaxed (&node.next)))
+        atomic_spin_nop ();
+    }
+
+  /* Pass down mcs lock holder to next spinner, synchronize-with
+   * atomic_load_acquire in mcs_lock.  */
+  atomic_store_release (&next->locked, 1);
+}
diff --git a/nptl/mcs_lock.h b/nptl/mcs_lock.h
new file mode 100644
index 0000000..5ee32f5
--- /dev/null
+++ b/nptl/mcs_lock.h
@@ -0,0 +1,23 @@ 
+/* MCS-style lock for queuing spinners
+   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/>.  */
+
+extern void mcs_lock (mcs_lock_t **lock)
+  __attribute__ ((visibility ("hidden")));
+
+extern void mcs_unlock (mcs_lock_t **lock)
+  __attribute__ ((visibility ("hidden")));
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 20ff3fd..d20481a 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -289,7 +289,7 @@  __pthread_initialize_minimal_internal (void)
 #ifdef __NR_set_robust_list
     pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
 				    - offsetof (pthread_mutex_t,
-						__data.__list.__next));
+						__data.__list.__list_t.__next));
     INTERNAL_SYSCALL_DECL (err);
     int res = INTERNAL_SYSCALL (set_robust_list, err, 2, &pd->robust_head,
 				sizeof (struct robust_list_head));
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 7f16ba9..7f5d8d2 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -67,7 +67,7 @@  static inline short max_adaptive_count (void)
 /* Internal mutex type value.  */
 enum
 {
-  PTHREAD_MUTEX_KIND_MASK_NP = 3,
+  PTHREAD_MUTEX_KIND_MASK_NP = 7,
 
   PTHREAD_MUTEX_ELISION_NP    = 256,
   PTHREAD_MUTEX_NO_ELISION_NP = 512,
@@ -88,6 +88,8 @@  enum
   = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ERRORCHECK_NP,
   PTHREAD_MUTEX_PI_ADAPTIVE_NP
   = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ADAPTIVE_NP,
+  PTHREAD_MUTEX_PI_QUEUESPINNER_NP
+  = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_QUEUESPINNER_NP,
   PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP
   = PTHREAD_MUTEX_PRIO_INHERIT_NP | PTHREAD_MUTEX_ROBUST_NORMAL_NP,
   PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP
@@ -105,6 +107,8 @@  enum
   = PTHREAD_MUTEX_PRIO_PROTECT_NP | PTHREAD_MUTEX_ERRORCHECK_NP,
   PTHREAD_MUTEX_PP_ADAPTIVE_NP
   = PTHREAD_MUTEX_PRIO_PROTECT_NP | PTHREAD_MUTEX_ADAPTIVE_NP,
+  PTHREAD_MUTEX_PP_QUEUESPINNER_NP
+  = PTHREAD_MUTEX_PRIO_PROTECT_NP | PTHREAD_MUTEX_QUEUESPINNER_NP,
   PTHREAD_MUTEX_ELISION_FLAGS_NP
   = PTHREAD_MUTEX_ELISION_NP | PTHREAD_MUTEX_NO_ELISION_NP,
 
diff --git a/nptl/pthread_mutex_init.c b/nptl/pthread_mutex_init.c
index 5cf290c..99f1707 100644
--- a/nptl/pthread_mutex_init.c
+++ b/nptl/pthread_mutex_init.c
@@ -111,6 +111,11 @@  __pthread_mutex_init (pthread_mutex_t *mutex,
 	return ENOTSUP;
 #endif
 
+      /* Robust mutex does not support the PTHREAD_MUTEX_QUEUESPINNER_NP
+         GNU extension.  */
+      if ((imutexattr->mutexkind & PTHREAD_MUTEX_QUEUESPINNER_NP) != 0)
+        return ENOTSUP;
+
       mutex_kind |= PTHREAD_MUTEX_ROBUST_NORMAL_NP;
     }
 
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 474b4df..db1b6d1 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -26,6 +26,7 @@ 
 #include <atomic.h>
 #include <lowlevellock.h>
 #include <stap-probe.h>
+#include <mcs_lock.h>
 
 #ifndef lll_lock_elision
 #define lll_lock_elision(lock, try_lock, private)	({ \
@@ -118,6 +119,35 @@  __pthread_mutex_lock (pthread_mutex_t *mutex)
       mutex->__data.__count = 1;
     }
   else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
+			 == PTHREAD_MUTEX_QUEUESPINNER_NP, 1))
+    {
+      if (! __is_smp)
+        goto simple;
+
+      if (LLL_MUTEX_TRYLOCK (mutex) != 0)
+        {
+          int cnt = 0;
+          int max_cnt = MIN (max_adaptive_count (),
+                            mutex->__data.__spins * 2 + 10);
+          int val = 0;
+
+          mcs_lock ((mcs_lock_t **)&mutex->__data.__list.mcs_lock);
+
+          do
+            {
+              atomic_spin_nop ();
+              val = atomic_load_relaxed (&mutex->__data.__lock);
+            }
+          while (val != 0 && ++cnt < max_cnt);
+
+          mcs_unlock ((mcs_lock_t **)&mutex->__data.__list.mcs_lock);
+          LLL_MUTEX_LOCK (mutex);
+
+          mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
+        }
+      assert (mutex->__data.__owner == 0);
+    }
+  else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
 			  == PTHREAD_MUTEX_ADAPTIVE_NP, 1))
     {
       if (! __is_smp)
@@ -179,7 +209,7 @@  __pthread_mutex_lock_full (pthread_mutex_t *mutex)
     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-		     &mutex->__data.__list.__next);
+		     &mutex->__data.__list.__list_t.__next);
       /* We need to set op_pending before starting the operation.  Also
 	 see comments at ENQUEUE_MUTEX.  */
       __asm ("" ::: "memory");
@@ -347,6 +377,7 @@  __pthread_mutex_lock_full (pthread_mutex_t *mutex)
     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_NORMAL_NP:
     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PI_QUEUESPINNER_NP:
     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
@@ -365,7 +396,7 @@  __pthread_mutex_lock_full (pthread_mutex_t *mutex)
 	  {
 	    /* Note: robust PI futexes are signaled by setting bit 0.  */
 	    THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-			   (void *) (((uintptr_t) &mutex->__data.__list.__next)
+			   (void *) (((uintptr_t) &mutex->__data.__list.__list_t.__next)
 				     | 1));
 	    /* We need to set op_pending before starting the operation.  Also
 	       see comments at ENQUEUE_MUTEX.  */
@@ -509,6 +540,7 @@  __pthread_mutex_lock_full (pthread_mutex_t *mutex)
     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PP_NORMAL_NP:
     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PP_QUEUESPINNER_NP:
       {
 	/* See concurrency notes regarding __kind in struct __pthread_mutex_s
 	   in sysdeps/nptl/bits/thread-shared-types.h.  */
diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
index 453b824..75bd734 100644
--- a/nptl/pthread_mutex_timedlock.c
+++ b/nptl/pthread_mutex_timedlock.c
@@ -25,6 +25,7 @@ 
 #include <atomic.h>
 #include <lowlevellock.h>
 #include <not-cancel.h>
+#include <mcs_lock.h>
 
 #include <stap-probe.h>
 
@@ -135,13 +136,37 @@  __pthread_mutex_timedlock (pthread_mutex_t *mutex,
 	  mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 	}
       break;
-
+    case PTHREAD_MUTEX_QUEUESPINNER_NP:
+      if (! __is_smp)
+        goto simple;
+
+      if (lll_trylock (mutex) != 0)
+        {
+          int cnt = 0;
+          int max_cnt = MIN (max_adaptive_count (),
+                            mutex->__data.__spins * 2 + 10);
+          int val = 0;
+
+          mcs_lock ((mcs_lock_t **)&mutex->__data.__list.mcs_lock);
+          do
+            {
+              atomic_spin_nop ();
+              val = atomic_load_relaxed (&mutex->__data.__lock);
+            }
+          while (val != 0 && ++cnt < max_cnt);
+          mcs_unlock ((mcs_lock_t **)&mutex->__data.__list.mcs_lock);
+          result = lll_timedlock(mutex->__data.__lock, abstime,
+                      PTHREAD_MUTEX_PSHARED (mutex));
+
+          mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
+        }
+      break;
     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-		     &mutex->__data.__list.__next);
+		     &mutex->__data.__list.__list_t.__next);
       /* We need to set op_pending before starting the operation.  Also
 	 see comments at ENQUEUE_MUTEX.  */
       __asm ("" ::: "memory");
@@ -335,6 +360,7 @@  __pthread_mutex_timedlock (pthread_mutex_t *mutex,
     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_NORMAL_NP:
     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PI_QUEUESPINNER_NP:
     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
@@ -353,7 +379,7 @@  __pthread_mutex_timedlock (pthread_mutex_t *mutex,
 	  {
 	    /* Note: robust PI futexes are signaled by setting bit 0.  */
 	    THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-			   (void *) (((uintptr_t) &mutex->__data.__list.__next)
+			   (void *) (((uintptr_t) &mutex->__data.__list.__list_t.__next)
 				     | 1));
 	    /* We need to set op_pending before starting the operation.  Also
 	       see comments at ENQUEUE_MUTEX.  */
@@ -516,6 +542,7 @@  __pthread_mutex_timedlock (pthread_mutex_t *mutex,
     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PP_NORMAL_NP:
     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PP_QUEUESPINNER_NP:
       {
 	/* See concurrency notes regarding __kind in struct __pthread_mutex_s
 	   in sysdeps/nptl/bits/thread-shared-types.h.  */
diff --git a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c
index fa90c1d..2545d15 100644
--- a/nptl/pthread_mutex_trylock.c
+++ b/nptl/pthread_mutex_trylock.c
@@ -78,6 +78,7 @@  __pthread_mutex_trylock (pthread_mutex_t *mutex)
       FORCE_ELISION (mutex, goto elision);
       /*FALL THROUGH*/
     case PTHREAD_MUTEX_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_QUEUESPINNER_NP:
     case PTHREAD_MUTEX_ERRORCHECK_NP:
       if (lll_trylock (mutex->__data.__lock) != 0)
 	break;
@@ -93,7 +94,7 @@  __pthread_mutex_trylock (pthread_mutex_t *mutex)
     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-		     &mutex->__data.__list.__next);
+		     &mutex->__data.__list.__list_t.__next);
 
       oldval = mutex->__data.__lock;
       do
@@ -196,6 +197,7 @@  __pthread_mutex_trylock (pthread_mutex_t *mutex)
     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_NORMAL_NP:
     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PI_QUEUESPINNER_NP:
     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
@@ -213,7 +215,7 @@  __pthread_mutex_trylock (pthread_mutex_t *mutex)
 	if (robust)
 	  /* Note: robust PI futexes are signaled by setting bit 0.  */
 	  THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-			 (void *) (((uintptr_t) &mutex->__data.__list.__next)
+			 (void *) (((uintptr_t) &mutex->__data.__list.__list_t.__next)
 				   | 1));
 
 	oldval = mutex->__data.__lock;
@@ -332,6 +334,7 @@  __pthread_mutex_trylock (pthread_mutex_t *mutex)
     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PP_NORMAL_NP:
     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PP_QUEUESPINNER_NP:
       {
 	/* See concurrency notes regarding __kind in struct __pthread_mutex_s
 	   in sysdeps/nptl/bits/thread-shared-types.h.  */
diff --git a/nptl/pthread_mutex_unlock.c b/nptl/pthread_mutex_unlock.c
index 68d04d5..abca8e7 100644
--- a/nptl/pthread_mutex_unlock.c
+++ b/nptl/pthread_mutex_unlock.c
@@ -78,6 +78,9 @@  __pthread_mutex_unlock_usercnt (pthread_mutex_t *mutex, int decr)
       goto normal;
     }
   else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
+			      == PTHREAD_MUTEX_QUEUESPINNER_NP, 1))
+    goto normal;
+  else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
 			      == PTHREAD_MUTEX_ADAPTIVE_NP, 1))
     goto normal;
   else
@@ -142,7 +145,7 @@  __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
     robust:
       /* Remove mutex from the list.  */
       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-		     &mutex->__data.__list.__next);
+		     &mutex->__data.__list.__list_t.__next);
       /* We must set op_pending before we dequeue the mutex.  Also see
 	 comments at ENQUEUE_MUTEX.  */
       __asm ("" ::: "memory");
@@ -213,6 +216,7 @@  __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_NORMAL_NP:
     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PI_QUEUESPINNER_NP:
     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
@@ -242,7 +246,7 @@  __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
 	  /* Remove mutex from the list.
 	     Note: robust PI futexes are signaled by setting bit 0.  */
 	  THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
-			 (void *) (((uintptr_t) &mutex->__data.__list.__next)
+			 (void *) (((uintptr_t) &mutex->__data.__list.__list_t.__next)
 				   | 1));
 	  /* We must set op_pending before we dequeue the mutex.  Also see
 	     comments at ENQUEUE_MUTEX.  */
@@ -311,6 +315,7 @@  __pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
 
     case PTHREAD_MUTEX_PP_NORMAL_NP:
     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
+    case PTHREAD_MUTEX_PP_QUEUESPINNER_NP:
       /* Always reset the owner field.  */
     pp:
       mutex->__data.__owner = 0;
diff --git a/nptl/pthread_mutexattr_settype.c b/nptl/pthread_mutexattr_settype.c
index 7d36cc3..c2382b4 100644
--- a/nptl/pthread_mutexattr_settype.c
+++ b/nptl/pthread_mutexattr_settype.c
@@ -25,7 +25,7 @@  __pthread_mutexattr_settype (pthread_mutexattr_t *attr, int kind)
 {
   struct pthread_mutexattr *iattr;
 
-  if (kind < PTHREAD_MUTEX_NORMAL || kind > PTHREAD_MUTEX_ADAPTIVE_NP)
+  if (kind < PTHREAD_MUTEX_NORMAL || kind > PTHREAD_MUTEX_QUEUESPINNER_NP)
     return EINVAL;
 
   /* Cannot distinguish between DEFAULT and NORMAL. So any settype
diff --git a/sysdeps/nptl/bits/thread-shared-types.h b/sysdeps/nptl/bits/thread-shared-types.h
index 05c94e7..1cf8874 100644
--- a/sysdeps/nptl/bits/thread-shared-types.h
+++ b/sysdeps/nptl/bits/thread-shared-types.h
@@ -79,15 +79,19 @@ 
 /* Common definition of pthread_mutex_t. */
 
 #if !__PTHREAD_MUTEX_USE_UNION
-typedef struct __pthread_internal_list
+typedef union __pthread_internal_list
 {
-  struct __pthread_internal_list *__prev;
-  struct __pthread_internal_list *__next;
+  struct {
+    union __pthread_internal_list *__prev;
+    union __pthread_internal_list *__next;
+  }__list_t;
+  void *mcs_lock;
 } __pthread_list_t;
 #else
-typedef struct __pthread_internal_slist
+typedef union __pthread_internal_slist
 {
-  struct __pthread_internal_slist *__next;
+  union __pthread_internal_slist *__next;
+  void *mcs_lock;
 } __pthread_slist_t;
 #endif
 
@@ -165,6 +169,13 @@  struct __pthread_mutex_s
   __PTHREAD_COMPAT_PADDING_END
 };
 
+struct mcs_lock
+{
+  struct mcs_lock *next;
+  int locked;
+};
+
+typedef struct mcs_lock mcs_lock_t;
 
 /* Common definition of pthread_cond_t. */
 
diff --git a/sysdeps/nptl/pthread.h b/sysdeps/nptl/pthread.h
index df049ab..4b4b80a 100644
--- a/sysdeps/nptl/pthread.h
+++ b/sysdeps/nptl/pthread.h
@@ -45,7 +45,8 @@  enum
   PTHREAD_MUTEX_TIMED_NP,
   PTHREAD_MUTEX_RECURSIVE_NP,
   PTHREAD_MUTEX_ERRORCHECK_NP,
-  PTHREAD_MUTEX_ADAPTIVE_NP
+  PTHREAD_MUTEX_ADAPTIVE_NP,
+  PTHREAD_MUTEX_QUEUESPINNER_NP
 #if defined __USE_UNIX98 || defined __USE_XOPEN2K8
   ,
   PTHREAD_MUTEX_NORMAL = PTHREAD_MUTEX_TIMED_NP,
@@ -85,14 +86,16 @@  enum
 
 #if __PTHREAD_MUTEX_HAVE_PREV
 # define PTHREAD_MUTEX_INITIALIZER \
-  { { 0, 0, 0, 0, 0, __PTHREAD_SPINS, { 0, 0 } } }
+  { { 0, 0, 0, 0, 0, __PTHREAD_SPINS, { { 0, 0 } } } }
 # ifdef __USE_GNU
 #  define PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP \
-  { { 0, 0, 0, 0, PTHREAD_MUTEX_RECURSIVE_NP, __PTHREAD_SPINS, { 0, 0 } } }
+  { { 0, 0, 0, 0, PTHREAD_MUTEX_RECURSIVE_NP, __PTHREAD_SPINS, { { 0, 0 } } } }
 #  define PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP \
-  { { 0, 0, 0, 0, PTHREAD_MUTEX_ERRORCHECK_NP, __PTHREAD_SPINS, { 0, 0 } } }
+  { { 0, 0, 0, 0, PTHREAD_MUTEX_ERRORCHECK_NP, __PTHREAD_SPINS, { { 0, 0 } } } }
 #  define PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP \
-  { { 0, 0, 0, 0, PTHREAD_MUTEX_ADAPTIVE_NP, __PTHREAD_SPINS, { 0, 0 } } }
+  { { 0, 0, 0, 0, PTHREAD_MUTEX_ADAPTIVE_NP, __PTHREAD_SPINS, { { 0, 0 } } } }
+#  define PTHREAD_QUEUESPINNER_MUTEX_INITIALIZER_NP \
+  { { 0, 0, 0, 0, PTHREAD_MUTEX_QUEUESPINNER_NP, __PTHREAD_SPINS, { { 0, 0 } } } }
 
 # endif
 #else
@@ -105,6 +108,8 @@  enum
   { { 0, 0, 0, PTHREAD_MUTEX_ERRORCHECK_NP, 0, { __PTHREAD_SPINS } } }
 #  define PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP \
   { { 0, 0, 0, PTHREAD_MUTEX_ADAPTIVE_NP, 0, { __PTHREAD_SPINS } } }
+#  define PTHREAD_QUEUESPINNER_MUTEX_INITIALIZER_NP \
+  { { 0, 0, 0, PTHREAD_MUTEX_QUEUESPINNER_NP, 0, { __PTHREAD_SPINS } } }
 
 # endif
 #endif
diff --git a/sysdeps/unix/sysv/linux/hppa/pthread.h b/sysdeps/unix/sysv/linux/hppa/pthread.h
index 11a024d..57c101c 100644
--- a/sysdeps/unix/sysv/linux/hppa/pthread.h
+++ b/sysdeps/unix/sysv/linux/hppa/pthread.h
@@ -46,6 +46,7 @@  enum
   PTHREAD_MUTEX_RECURSIVE_NP,
   PTHREAD_MUTEX_ERRORCHECK_NP,
   PTHREAD_MUTEX_ADAPTIVE_NP
+  PTHREAD_MUTEX_QUEUESPINNER_NP,
 #if defined __USE_UNIX98 || defined __USE_XOPEN2K8
   ,
   PTHREAD_MUTEX_NORMAL = PTHREAD_MUTEX_TIMED_NP,
@@ -95,6 +96,9 @@  enum
 # define PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP \
   { { 0, 0, 0, PTHREAD_MUTEX_ADAPTIVE_NP, { 0, 0, 0, 0 }, 0, \
       { __PTHREAD_SPINS }, { 0, 0 } } }
+# define PTHREAD_QUEUESPINNER_MUTEX_INITIALIZER_NP \
+  { { 0, 0, 0, PTHREAD_MUTEX_QUEUESPINNER_NP, { 0, 0, 0, 0 }, 0, \
+      { __PTHREAD_SPINS }, { 0, 0 } } }
 #endif