From 4fe523741e75afac00535af59a05778306148f2c Mon Sep 17 00:00:00 2001
From: Maksym Sobolyev <sobomax@sippysoft.com>
Date: Wed, 8 Mar 2017 08:06:38 -0800
Subject: [PATCH] Implement new locking method based around FreeBSD futex-like
 _umtx_op(2) locking primitives, which allows for process-shared
 kernel-assisted mutexes.

---
 Makefile.conf.template |  1 +
 Makefile.defs          |  5 +++++
 lock_alloc.h           |  2 +-
 lock_ops.h             | 51 +++++++++++++++++++++++++++++++++++++++++-
 version.h              |  9 +++++++-
 5 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/Makefile.conf.template b/Makefile.conf.template
index 749faa229f4..6cc49393f16 100644
--- a/Makefile.conf.template
+++ b/Makefile.conf.template
@@ -84,6 +84,7 @@ DEFS+= -DDBG_MALLOC #Enables debugging for memory allocators
 #DEFS+= -DUSE_FUTEX #Uses linux futexs with fast architecture specific locking
 #DEFS+= -DUSE_SYSV_SEM #Uses SYSV sems for locking ( slower & limited number of locks
 #DEFS+= -DUSE_PTHREAD_MUTEX #Uses pthread mutexes for locking
+#DEFS+= -DUSE_UMUTEX_MUTEX #Uses FreeBSD-specific low-level mutexes for locking
 #DEFS+= -DUSE_POSIX_SEM #Uses POSIX sems for locking
 #DEFS+= -DBUSY_WAIT #Uses busy waiting on the lock
 #DEFS+= -DDBG_LOCK #Attach debug info to all lock structures
diff --git a/Makefile.defs b/Makefile.defs
index 26106f5172f..a0f604dff13 100644
--- a/Makefile.defs
+++ b/Makefile.defs
@@ -752,6 +752,7 @@ ifeq ($(ARCH), alpha)
 endif
 
 # decide on the locking type
+ifeq (,$(findstring USE_UMUTEX_MUTEX, $(DEFS)))
 ifeq (,$(findstring USE_PTHREAD_MUTEX, $(DEFS)))
 ifeq (,$(findstring USE_POSIX_SEM, $(DEFS)))
 ifeq (,$(findstring USE_SYSV_SEM, $(DEFS)))
@@ -771,6 +772,10 @@ else
 	## USE_PTHREAD_MUTEX was manually forced from .conf
 	found_lock_method=yes
 endif
+else
+        ## USE_UMUTEX_MUTEX was manually forced from .conf
+        found_lock_method=yes
+endif
 
 CFLAGS=$(shell echo "$${CFLAGS}")
 LDFLAGS+=
diff --git a/lock_alloc.h b/lock_alloc.h
index 7a1d9bb54dc..eaa23864137 100644
--- a/lock_alloc.h
+++ b/lock_alloc.h
@@ -54,7 +54,7 @@
 #include "mem/mem.h"
 #include "mem/shm_mem.h"
 
-#if defined(FAST_LOCK) || defined(USE_PTHREAD_MUTEX) || defined(USE_POSIX_SEM)
+#if defined(FAST_LOCK) || defined(USE_PTHREAD_MUTEX) || defined(USE_POSIX_SEM) || defined(USE_UMUTEX_MUTEX)
 /* simple locks*/
 #define lock_alloc() shm_malloc(sizeof(gen_lock_t))
 #define lock_dealloc(lock) shm_free((void*)lock)
diff --git a/lock_ops.h b/lock_ops.h
index 38de905bb4c..8c7f0740fce 100644
--- a/lock_ops.h
+++ b/lock_ops.h
@@ -127,6 +127,55 @@ inline static gen_lock_t* lock_init(gen_lock_t* lock)
 #define lock_get(lock) pthread_mutex_lock(lock)
 #define lock_release(lock) pthread_mutex_unlock(lock)
 
+#elif defined USE_UMUTEX_MUTEX
+# if !defined(USE_UMUTEX_MUTEX_DECL)
+#  define USE_UMUTEX_MUTEX_DECL 1
+#include <sys/types.h>
+
+#include <errno.h>
+#include <string.h>
+
+#define u_long unsigned long
+#include <sys/umtx.h>
+
+typedef struct umutex gen_lock_t;
+
+#define lock_destroy(lock) /* do nothing */
+
+inline static int
+_umtx_op_err(void *obj, int op, u_long val, void *uaddr, void *uaddr2)
+{
+
+        if (_umtx_op(obj, op, val, uaddr, uaddr2) == -1)
+                return (errno);
+        return (0);
+}
+
+inline static gen_lock_t *
+lock_init(gen_lock_t *lock)
+{
+
+    memset(lock, '\0', sizeof(gen_lock_t));
+    lock->m_flags = USYNC_PROCESS_SHARED;
+
+    return (lock);
+}
+
+inline static int
+lock_get(gen_lock_t *lock)
+{
+
+    return  (_umtx_op_err(lock, UMTX_OP_MUTEX_LOCK, 0, 0, 0));
+}
+
+inline static int
+lock_release(gen_lock_t *lock)
+{
+
+    return (_umtx_op_err(lock, UMTX_OP_MUTEX_UNLOCK, 0, 0, 0));
+}
+
+# endif /* USE_UMUTEX_MUTEX_DECL */
 #elif defined USE_POSIX_SEM
 #include <semaphore.h>
 
@@ -248,7 +297,7 @@ inline static void lock_release(gen_lock_t* lock)
 
 /* lock sets */
 
-#if defined(FAST_LOCK) || defined(USE_PTHREAD_MUTEX) || defined(USE_POSIX_SEM)
+#if defined(FAST_LOCK) || defined(USE_PTHREAD_MUTEX) || defined(USE_POSIX_SEM) || defined(USE_UMUTEX_MUTEX)
 #define GEN_LOCK_T_PREFERED
 
 struct gen_lock_set_t_ {
diff --git a/version.h b/version.h
index 00d29f09fce..d7c1c9ca9c1 100644
--- a/version.h
+++ b/version.h
@@ -153,6 +153,12 @@
 #define USE_PTHREAD_MUTEX_STR ""
 #endif
 
+#ifdef USE_UMUTEX_MUTEX
+#define USE_UMUTEX_MUTEX_STR ", USE_UMUTEX_MUTEX"
+#else
+#define USE_UMUTEX_MUTEX_STR ""
+#endif
+
 #ifdef USE_POSIX_SEM
 #define USE_POSIX_SEM_STR ", USE_POSIX_SEM"
 #else
@@ -183,7 +189,8 @@
 	SHM_MMAP_STR PKG_MALLOC_STR VQ_MALLOC_STR QM_MALLOC_STR F_MALLOC_STR \
 	HP_MALLOC_STR USE_SHM_MEM_STR DBG_MALLOC_STR \
 	DEBUG_DMALLOC_STR QM_JOIN_FREE_STR FAST_LOCK_STR NOSMP_STR \
-	USE_PTHREAD_MUTEX_STR USE_POSIX_SEM_STR USE_SYSV_SEM_STR DBG_LOCK_STR
+	USE_PTHREAD_MUTEX_STR USE_UMUTEX_MUTEX_STR USE_POSIX_SEM_STR \
+	USE_SYSV_SEM_STR DBG_LOCK_STR
 
 
 #endif