From 3fc23e2542d89712e6104331e95c648fc52a9b35 Mon Sep 17 00:00:00 2001
From: Ruslan Ermilov <ru@nginx.com>
Date: Sat, 21 Mar 2015 14:05:08 +0300
Subject: Core: read/write locks.

---
 src/core/ngx_core.h   |   1 +
 src/core/ngx_rwlock.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/core/ngx_rwlock.h |  21 ++++++++++
 3 files changed, 134 insertions(+)
 create mode 100644 src/core/ngx_rwlock.c
 create mode 100644 src/core/ngx_rwlock.h

(limited to 'src/core')

diff --git a/src/core/ngx_core.h b/src/core/ngx_core.h
index bc1d43f98..e8031ef60 100644
--- a/src/core/ngx_core.h
+++ b/src/core/ngx_core.h
@@ -68,6 +68,7 @@ typedef void (*ngx_connection_handler_pt)(ngx_connection_t *c);
 #endif
 #include <ngx_radix_tree.h>
 #include <ngx_times.h>
+#include <ngx_rwlock.h>
 #include <ngx_shmtx.h>
 #include <ngx_slab.h>
 #include <ngx_inet.h>
diff --git a/src/core/ngx_rwlock.c b/src/core/ngx_rwlock.c
new file mode 100644
index 000000000..066c67de8
--- /dev/null
+++ b/src/core/ngx_rwlock.c
@@ -0,0 +1,112 @@
+
+/*
+ * Copyright (C) Ruslan Ermilov
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+
+
+#if (NGX_HAVE_ATOMIC_OPS)
+
+
+#define NGX_RWLOCK_SPIN   2048
+#define NGX_RWLOCK_WLOCK  ((ngx_atomic_uint_t) -1)
+
+
+void
+ngx_rwlock_wlock(ngx_atomic_t *lock)
+{
+    ngx_uint_t  i, n;
+
+    for ( ;; ) {
+
+        if (*lock == 0 && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK)) {
+            return;
+        }
+
+        if (ngx_ncpu > 1) {
+
+            for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) {
+
+                for (i = 0; i < n; i++) {
+                    ngx_cpu_pause();
+                }
+
+                if (*lock == 0
+                    && ngx_atomic_cmp_set(lock, 0, NGX_RWLOCK_WLOCK))
+                {
+                    return;
+                }
+            }
+        }
+
+        ngx_sched_yield();
+    }
+}
+
+
+void
+ngx_rwlock_rlock(ngx_atomic_t *lock)
+{
+    ngx_uint_t         i, n;
+    ngx_atomic_uint_t  readers;
+
+    for ( ;; ) {
+        readers = *lock;
+
+        if (readers != NGX_RWLOCK_WLOCK
+            && ngx_atomic_cmp_set(lock, readers, readers + 1))
+        {
+            return;
+        }
+
+        if (ngx_ncpu > 1) {
+
+            for (n = 1; n < NGX_RWLOCK_SPIN; n <<= 1) {
+
+                for (i = 0; i < n; i++) {
+                    ngx_cpu_pause();
+                }
+
+                readers = *lock;
+
+                if (readers != NGX_RWLOCK_WLOCK
+                    && ngx_atomic_cmp_set(lock, readers, readers + 1))
+                {
+                    return;
+                }
+            }
+        }
+
+        ngx_sched_yield();
+    }
+}
+
+
+void
+ngx_rwlock_unlock(ngx_atomic_t *lock)
+{
+    ngx_atomic_uint_t  readers;
+
+    readers = *lock;
+
+    if (readers == NGX_RWLOCK_WLOCK) {
+        *lock = 0;
+        return;
+    }
+
+    for ( ;; ) {
+
+        if (ngx_atomic_cmp_set(lock, readers, readers - 1)) {
+            return;
+        }
+
+        readers = *lock;
+    }
+}
+
+
+#endif
diff --git a/src/core/ngx_rwlock.h b/src/core/ngx_rwlock.h
new file mode 100644
index 000000000..8b16eca20
--- /dev/null
+++ b/src/core/ngx_rwlock.h
@@ -0,0 +1,21 @@
+
+/*
+ * Copyright (C) Ruslan Ermilov
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#ifndef _NGX_RWLOCK_H_INCLUDED_
+#define _NGX_RWLOCK_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+
+
+void ngx_rwlock_wlock(ngx_atomic_t *lock);
+void ngx_rwlock_rlock(ngx_atomic_t *lock);
+void ngx_rwlock_unlock(ngx_atomic_t *lock);
+
+
+#endif /* _NGX_RWLOCK_H_INCLUDED_ */
-- 
cgit