emu: fixed race condition

emu/dis340.c

@@ -845,6 +845,10 @@ renderthread(void *arg)
 		SDL_TEXTUREACCESS_STREAMING, 1024, 1024);
 	SDL_SetTextureBlendMode(tex, SDL_BLENDMODE_BLEND);
 
+	lock(&initlock);
+	awaitinit--;
+	unlock(&initlock);
+
 	for(;;){
 #ifdef JUSTTESTING
 		while(SDL_PollEvent(&ev))
@@ -1017,6 +1021,10 @@ makedis(int argc, char *argv[])
 	t = (Task){ nil, discycle, dis, 20, 0 };
 	addtask(t);
 
+	lock(&initlock);
+	awaitinit++;
+	unlock(&initlock);
+
 	/* There's a race somewhere here */
 	threadcreate(renderthread, dis);
 

emu/main_panel.c

@@ -55,6 +55,8 @@ struct SwDigit
 
 static SDL_Window *window;
 static SDL_Renderer *renderer;
+Lock initlock;
+volatile int awaitinit;
 
 Image*
 mustloadimg(const char *path)
@@ -903,6 +905,8 @@ void main340(void);
 	if(apr == nil || tty == nil || ptr == nil || ptp == nil)
 		err("need APR, TTY, PTR and PTP");
 
+	while(awaitinit);
+
 	cmdchans[0] = chancreate(sizeof(char*), 1);
 	cmdchans[1] = chancreate(sizeof(void*), 1);
 	t = (Task){ nil, readcmdchan, cmdchans, 10, 0 };

emu/pdp6.h

@@ -42,6 +42,9 @@ void *rtcthread(void *p);
 int dofile(const char *path);
 void defaultconfig(void);
 
+extern Lock initlock;
+extern volatile int awaitinit;
+
 enum {
 	MAXPULSE = 20
 };