From a8ba24aecfbeaa955c07d644ceb9e6f35290f3f4 Mon Sep 17 00:00:00 2001
From: gbeauche <>
Date: Sat, 25 Jun 2005 11:40:29 +0000
Subject: [PATCH] Use fast spinlocks only for small enough atomic operations.
 Otherwise, you run into some performance problems in e.g. video graphics
 experience because of busywaits in the current spin_lock() implementation.

---
 BasiliskII/src/Unix/video_vosf.h | 16 ++++++++--------
 SheepShaver/src/Unix/sysdeps.h   | 15 ++++++++-------
 SheepShaver/src/Unix/video_x.cpp | 20 ++++++++++----------
 3 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/BasiliskII/src/Unix/video_vosf.h b/BasiliskII/src/Unix/video_vosf.h
index 90ed0747..720b1d00 100644
--- a/BasiliskII/src/Unix/video_vosf.h
+++ b/BasiliskII/src/Unix/video_vosf.h
@@ -168,18 +168,18 @@ static inline int find_next_page_clear(int page)
 #endif
 }
 
-#ifdef HAVE_SPINLOCKS
-static spinlock_t vosf_lock = SPIN_LOCK_UNLOCKED;				// Mutex to protect frame buffer (dirtyPages in fact)
-#define LOCK_VOSF spin_lock(&vosf_lock)
-#define UNLOCK_VOSF spin_unlock(&vosf_lock)
+#if defined(HAVE_PTHREADS)
+static pthread_mutex_t vosf_lock = PTHREAD_MUTEX_INITIALIZER;	// Mutex to protect frame buffer (dirtyPages in fact)
+#define LOCK_VOSF pthread_mutex_lock(&vosf_lock);
+#define UNLOCK_VOSF pthread_mutex_unlock(&vosf_lock);
 #elif defined(_WIN32)
 static mutex_t vosf_lock;										// Mutex to protect frame buffer (dirtyPages in fact)
 #define LOCK_VOSF vosf_lock.lock();
 #define UNLOCK_VOSF vosf_lock.unlock();
-#elif defined(HAVE_PTHREADS)
-static pthread_mutex_t vosf_lock = PTHREAD_MUTEX_INITIALIZER;	// Mutex to protect frame buffer (dirtyPages in fact)
-#define LOCK_VOSF pthread_mutex_lock(&vosf_lock);
-#define UNLOCK_VOSF pthread_mutex_unlock(&vosf_lock);
+#elif defined(HAVE_SPINLOCKS)
+static spinlock_t vosf_lock = SPIN_LOCK_UNLOCKED;				// Mutex to protect frame buffer (dirtyPages in fact)
+#define LOCK_VOSF spin_lock(&vosf_lock)
+#define UNLOCK_VOSF spin_unlock(&vosf_lock)
 #else
 #define LOCK_VOSF
 #define UNLOCK_VOSF
diff --git a/SheepShaver/src/Unix/sysdeps.h b/SheepShaver/src/Unix/sysdeps.h
index e1d94b99..56d9623c 100644
--- a/SheepShaver/src/Unix/sysdeps.h
+++ b/SheepShaver/src/Unix/sysdeps.h
@@ -372,7 +372,8 @@ typedef volatile int spinlock_t;
 
 static const spinlock_t SPIN_LOCK_UNLOCKED = 0;
 
-#if HAVE_TEST_AND_SET
+#if defined(HAVE_TEST_AND_SET) && defined(HAVE_PTHREADS)
+// There is nothing to lock if we are not in an multithreaded environment
 #define HAVE_SPINLOCKS 1
 static inline void spin_lock(spinlock_t *lock)
 {
@@ -442,16 +443,16 @@ typedef struct rgb_color {
 } rgb_color;
 
 // X11 display fast locks
-#ifdef HAVE_SPINLOCKS
-#define X11_LOCK_TYPE spinlock_t
-#define X11_LOCK_INIT SPIN_LOCK_UNLOCKED
-#define XDisplayLock() spin_lock(&x_display_lock)
-#define XDisplayUnlock() spin_unlock(&x_display_lock)
-#elif defined(HAVE_PTHREADS)
+#if defined(HAVE_PTHREADS)
 #define X11_LOCK_TYPE pthread_mutex_t
 #define X11_LOCK_INIT PTHREAD_MUTEX_INITIALIZER
 #define XDisplayLock() pthread_mutex_lock(&x_display_lock);
 #define XDisplayUnlock() pthread_mutex_unlock(&x_display_lock);
+#elif defined(HAVE_SPINLOCKS)
+#define X11_LOCK_TYPE spinlock_t
+#define X11_LOCK_INIT SPIN_LOCK_UNLOCKED
+#define XDisplayLock() spin_lock(&x_display_lock)
+#define XDisplayUnlock() spin_unlock(&x_display_lock)
 #else
 #define XDisplayLock()
 #define XDisplayUnlock()
diff --git a/SheepShaver/src/Unix/video_x.cpp b/SheepShaver/src/Unix/video_x.cpp
index 5bffd1e1..816b002c 100644
--- a/SheepShaver/src/Unix/video_x.cpp
+++ b/SheepShaver/src/Unix/video_x.cpp
@@ -168,28 +168,28 @@ static int num_x_video_modes;
 #endif
 
 // Mutex to protect palette
-#ifdef HAVE_SPINLOCKS
-static spinlock_t x_palette_lock = SPIN_LOCK_UNLOCKED;
-#define LOCK_PALETTE spin_lock(&x_palette_lock)
-#define UNLOCK_PALETTE spin_unlock(&x_palette_lock)
-#elif defined(HAVE_PTHREADS)
+#if defined(HAVE_PTHREADS)
 static pthread_mutex_t x_palette_lock = PTHREAD_MUTEX_INITIALIZER;
 #define LOCK_PALETTE pthread_mutex_lock(&x_palette_lock)
 #define UNLOCK_PALETTE pthread_mutex_unlock(&x_palette_lock)
+#elif defined(HAVE_SPINLOCKS)
+static spinlock_t x_palette_lock = SPIN_LOCK_UNLOCKED;
+#define LOCK_PALETTE spin_lock(&x_palette_lock)
+#define UNLOCK_PALETTE spin_unlock(&x_palette_lock)
 #else
 #define LOCK_PALETTE
 #define UNLOCK_PALETTE
 #endif
 
 // Mutex to protect frame buffer
-#ifdef HAVE_SPINLOCKS
-static spinlock_t frame_buffer_lock = SPIN_LOCK_UNLOCKED;
-#define LOCK_FRAME_BUFFER spin_lock(&frame_buffer_lock)
-#define UNLOCK_FRAME_BUFFER spin_unlock(&frame_buffer_lock)
-#elif defined(HAVE_PTHREADS)
+#if defined(HAVE_PTHREADS)
 static pthread_mutex_t frame_buffer_lock = PTHREAD_MUTEX_INITIALIZER;
 #define LOCK_FRAME_BUFFER pthread_mutex_lock(&frame_buffer_lock);
 #define UNLOCK_FRAME_BUFFER pthread_mutex_unlock(&frame_buffer_lock);
+#elif defined(HAVE_SPINLOCKS)
+static spinlock_t frame_buffer_lock = SPIN_LOCK_UNLOCKED;
+#define LOCK_FRAME_BUFFER spin_lock(&frame_buffer_lock)
+#define UNLOCK_FRAME_BUFFER spin_unlock(&frame_buffer_lock)
 #else
 #define LOCK_FRAME_BUFFER
 #define UNLOCK_FRAME_BUFFER