Initial version.

src/nxt_spinlock.c

@@ -0,0 +1,152 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) NGINX, Inc.
+ */
+
+#include <nxt_main.h>
+
+
+/*
+ * Linux supports pthread spinlocks since glibc 2.3.  Spinlock is an
+ * atomic integer with zero initial value.  On i386/amd64 however the
+ * initial value is one.  Spinlock never yields control.
+ *
+ * FreeBSD 5.2 and Solaris 10 support pthread spinlocks.  Spinlock is a
+ * structure and uses mutex implementation so it must be initialized by
+ * by pthread_spin_init() and destroyed by pthread_spin_destroy().
+ */
+
+#if (NXT_HAVE_MACOSX_SPINLOCK)
+
+/*
+ * OSSpinLockLock() tries to acquire a lock atomically.  If the lock is
+ * busy, on SMP system it tests the lock 1000 times in a tight loop with
+ * "pause" instruction.  If the lock has been released, OSSpinLockLock()
+ * tries to acquire it again.  On failure it goes again in the tight loop.
+ * If the lock has not been released during spinning in the loop or
+ * on UP system, OSSpinLockLock() calls thread_switch() to run 1ms
+ * with depressed (the lowest) priority.
+ */
+
+void
+nxt_thread_spin_lock(nxt_thread_spinlock_t *lock)
+{
+    nxt_thread_log_debug("OSSpinLockLock(%p) enter", lock);
+
+    OSSpinLockLock(lock);
+}
+
+
+nxt_bool_t
+nxt_thread_spin_trylock(nxt_thread_spinlock_t *lock)
+{
+    nxt_thread_log_debug("OSSpinLockTry(%p) enter", lock);
+
+    if (OSSpinLockTry(lock)) {
+        return 1;
+    }
+
+    nxt_thread_log_debug("OSSpinLockTry(%p) failed", lock);
+
+    return 0;
+}
+
+
+void
+nxt_thread_spin_unlock(nxt_thread_spinlock_t *lock)
+{
+    OSSpinLockUnlock(lock);
+
+    nxt_thread_log_debug("OSSpinLockUnlock(%p) exit", lock);
+}
+
+
+#else
+
+
+/* It should be adjusted with the "spinlock_count" directive. */
+static nxt_uint_t  nxt_spinlock_count = 1000;
+
+
+void
+nxt_thread_spin_init(nxt_uint_t ncpu, nxt_uint_t count)
+{
+    switch (ncpu) {
+
+    case 0:
+        /* Explicit spinlock count. */
+        nxt_spinlock_count = count;
+        break;
+
+    case 1:
+        /* Spinning is useless on UP. */
+        nxt_spinlock_count = 0;
+        break;
+
+    default:
+        /*
+         * SMP.
+         *
+         * TODO: The count should be 10 on a virtualized system
+         * since virtualized CPUs may share the same physical CPU.
+         */
+        nxt_spinlock_count = 1000;
+        break;
+    }
+}
+
+
+void
+nxt_thread_spin_lock(nxt_thread_spinlock_t *lock)
+{
+    nxt_uint_t  n;
+
+    nxt_thread_log_debug("spin_lock(%p) enter", lock);
+
+    for ( ;; ) {
+
+    again:
+
+        if (nxt_fast_path(nxt_atomic_try_lock(lock))) {
+            return;
+        }
+
+        for (n = nxt_spinlock_count; n != 0; n--) {
+
+            nxt_cpu_pause();
+
+            if (*lock == 0) {
+                goto again;
+            }
+        }
+
+        nxt_thread_yield();
+    }
+}
+
+
+nxt_bool_t
+nxt_thread_spin_trylock(nxt_thread_spinlock_t *lock)
+{
+    nxt_thread_log_debug("spin_trylock(%p) enter", lock);
+
+    if (nxt_fast_path(nxt_atomic_try_lock(lock))) {
+        return 1;
+    }
+
+    nxt_thread_log_debug("spin_trylock(%p) failed", lock);
+
+    return 0;
+}
+
+
+void
+nxt_thread_spin_unlock(nxt_thread_spinlock_t *lock)
+{
+    nxt_atomic_release(lock);
+
+    nxt_thread_log_debug("spin_unlock(%p) exit", lock);
+}
+
+#endif