From e5888a1ffdae813d7575f5fb02275c6bb07e5199 Mon Sep 17 00:00:00 2001
From: Taru Karttunen <taruti@taruti.net>
Date: Wed, 30 Mar 2011 15:46:40 +0300
Subject: Import sources from 2011-03-30 iso image

---
 sys/src/cmd/unix/drawterm/libc/lock.c | 120 ++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100755 sys/src/cmd/unix/drawterm/libc/lock.c

(limited to 'sys/src/cmd/unix/drawterm/libc/lock.c')

diff --git a/sys/src/cmd/unix/drawterm/libc/lock.c b/sys/src/cmd/unix/drawterm/libc/lock.c
new file mode 100755
index 000000000..07d435256
--- /dev/null
+++ b/sys/src/cmd/unix/drawterm/libc/lock.c
@@ -0,0 +1,120 @@
+#include <u.h>
+#include <libc.h>
+
+#ifdef PTHREAD
+
+static pthread_mutex_t initmutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void
+lockinit(Lock *lk)
+{
+	pthread_mutexattr_t attr;
+
+	pthread_mutex_lock(&initmutex);
+	if(lk->init == 0){
+		pthread_mutexattr_init(&attr);
+		pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL);
+		pthread_mutex_init(&lk->mutex, &attr);
+		pthread_mutexattr_destroy(&attr);
+		lk->init = 1;
+	}
+	pthread_mutex_unlock(&initmutex);
+}
+
+void
+lock(Lock *lk)
+{
+	if(!lk->init)
+		lockinit(lk);
+	if(pthread_mutex_lock(&lk->mutex) != 0)
+		abort();
+}
+
+int
+canlock(Lock *lk)
+{
+	int r;
+
+	if(!lk->init)
+		lockinit(lk);
+	r = pthread_mutex_trylock(&lk->mutex);
+	if(r == 0)
+		return 1;
+	if(r == EBUSY)
+		return 0;
+	abort();
+}
+
+void
+unlock(Lock *lk)
+{
+	if(pthread_mutex_unlock(&lk->mutex) != 0)
+		abort();
+}
+
+#else 
+
+/* old, non-pthread systems */
+
+int
+canlock(Lock *lk)
+{
+	return !tas(&lk->key);
+}
+
+void
+lock(Lock *lk)
+{
+	int i;
+
+	/* easy case */
+	if(canlock(lk))
+		return;
+
+	/* for multi processor machines */
+	for(i=0; i<100; i++)
+		if(canlock(lk))
+			return;
+
+	for(i=0; i<100; i++) {
+		osyield();
+		if(canlock(lk))
+			return;
+	}
+
+	/* looking bad - make sure it is not a priority problem */
+	for(i=0; i<12; i++) {
+		osmsleep(1<<i);
+		if(canlock(lk))
+			return;
+	}
+
+	/* we are in trouble */
+	for(;;) {
+		if(canlock(lk))
+			return;
+		iprint("lock loop %ld: val=%d &lock=%ux pc=%p\n", getpid(), lk->key, lk, getcallerpc(&lk));
+		osmsleep(1000);
+	}
+}
+
+void
+unlock(Lock *lk)
+{
+	assert(lk->key);
+	lk->key = 0;
+}
+
+#endif
+
+void
+ilock(Lock *lk)
+{
+	lock(lk);
+}
+
+void
+iunlock(Lock *lk)
+{
+	unlock(lk);
+}
-- 
cgit v1.2.3