Partial restart of threads has proven to be unsuccessful so reinstate device re-initialisation to restart GPUs.

Do this by having a reinit thread that is told via a queue which device to restart.
If this thread fails to return from opencl code, it should not interrupt the workings of other devices.

main.c

@@ -184,6 +184,8 @@ int longpoll_thr_id;
 static int stage_thr_id;
 static int watchdog_thr_id;
 static int input_thr_id;
+static int gpur_thr_id;
+static int cpur_thr_id;
 static int total_threads;
 
 struct work_restart *work_restart = NULL;
@@ -3340,6 +3342,7 @@ static void restart_longpoll(void)
 
 static void *reinit_cpu(void *userdata)
 {
+	pthread_detach(pthread_self());
 #if 0
 	struct cgpu_info *cgpu = (struct cgpu_info *)userdata;
 	int cpu = cgpu->cpu_gpu;
@@ -3371,35 +3374,52 @@ static void *reinit_cpu(void *userdata)
 }
 
 #ifdef HAVE_OPENCL
+/* We have only one thread that ever re-initialises GPUs, thus if any GPU
+ * init command fails due to a completely wedged GPU, the thread will never
+ * return, unable to harm other GPUs. If it does return, it means we only had
+ * a soft failure and then the reinit_gpu thread is ready to tackle another
+ * GPU */
 static void *reinit_gpu(void *userdata)
 {
-	struct cgpu_info *cgpu = (struct cgpu_info *)userdata;
-	int gpu = cgpu->cpu_gpu;
+	struct thr_info *mythr = userdata;
+	struct cgpu_info *cgpu;
 	struct thr_info *thr;
 	char name[256];
 	int thr_id;
-	_clState *clState;
+	int gpu;
+
+	pthread_detach(pthread_self());
+
+select_cgpu:
+	cgpu = tq_pop(mythr->q, NULL);
+	if (!cgpu)
+		goto out;
+
+	if (clDevicesNum() != nDevs) {
+		applog(LOG_WARNING, "Hardware not reporting same number of active devices, will not attempt to restart GPU");
+		goto out;
+	}
 
-	/* Send threads message to stop */
+	gpu = cgpu->cpu_gpu;
 	gpu_devices[gpu] = false;
-	sleep(5);
 
 	for (thr_id = 0; thr_id < gpu_threads; thr_id ++) {
 		if (dev_from_id(thr_id) != gpu)
 			continue;
 
-		clState = clStates[thr_id];
-		/* Send it a command. If it responds we can restart */
-		applog(LOG_WARNING, "Attempting to send GPU command");
-		clFlush(clState->commandQueue);
-		clFinish(clState->commandQueue);
-
 		thr = &thr_info[thr_id];
 		thr->rolling = thr->cgpu->rolling = 0;
 		if (!pthread_cancel(*thr->pth)) {
-			applog(LOG_WARNING, "Thread still exists, killing it off");
+			applog(LOG_WARNING, "Thread %d still exists, killing it off", thr_id);
 		} else
-			applog(LOG_WARNING, "Thread no longer exists");
+			applog(LOG_WARNING, "Thread %d no longer exists", thr_id);
+	}
+
+	for (thr_id = 0; thr_id < gpu_threads; thr_id ++) {
+		if (dev_from_id(thr_id) != gpu)
+			continue;
+
+		thr = &thr_info[thr_id];
 
 		/* Lose this ram cause we may get stuck here! */
 		//tq_freeze(thr->q);
@@ -3410,13 +3430,12 @@ static void *reinit_gpu(void *userdata)
 
 		/* Lose this ram cause we may dereference in the dying thread! */
 		//free(clState);
-		applog(LOG_WARNING, "Command successful, attempting to reinit device");
 
 		applog(LOG_INFO, "Reinit GPU thread %d", thr_id);
-		clState = initCl(gpu, name, sizeof(name));
-		if (!clState) {
+		clStates[thr_id] = initCl(gpu, name, sizeof(name));
+		if (!clStates[thr_id]) {
 			applog(LOG_ERR, "Failed to reinit GPU thread %d", thr_id);
-			return NULL;
+			goto out;
 		}
 		applog(LOG_INFO, "initCl() finished. Found %s", name);
 
@@ -3427,14 +3446,17 @@ static void *reinit_gpu(void *userdata)
 		applog(LOG_WARNING, "Thread %d restarted", thr_id);
 	}
 
-	/* Try to re-enable it */
 	gpu_devices[gpu] = true;
 	for (thr_id = 0; thr_id < gpu_threads; thr_id ++) {
+		if (dev_from_id(thr_id) != gpu)
+			continue;
+
 		thr = &thr_info[thr_id];
-		if (dev_from_id(thr_id) == gpu)
-			tq_push(thr->q, &ping);
+		tq_push(thr->q, &ping);
 	}
 
+	goto select_cgpu;
+out:
 	return NULL;
 }
 #else
@@ -3445,16 +3467,10 @@ static void *reinit_gpu(void *userdata)
 
 static void reinit_device(struct cgpu_info *cgpu)
 {
-	pthread_t resus_thread;
-	void *reinit;
-
 	if (cgpu->is_gpu)
-		reinit = reinit_gpu;
+		tq_push(thr_info[gpur_thr_id].q, cgpu);
 	else
-		reinit = reinit_cpu;
-
-	if (unlikely(pthread_create(&resus_thread, NULL, reinit, (void *)cgpu)))
-		applog(LOG_ERR, "Failed to create reinit thread");
+		tq_push(thr_info[cpur_thr_id].q, cgpu);
 }
 
 /* Determine which are the first threads belonging to a device and if they're
@@ -3811,7 +3827,7 @@ static void fork_monitor()
 
 int main (int argc, char *argv[])
 {
-	unsigned int i, j = 0, x, y, pools_active = 0;
+	unsigned int i, x, y, pools_active = 0;
 	struct sigaction handler;
 	struct thr_info *thr;
 	char name[256];
@@ -3969,7 +3985,7 @@ int main (int argc, char *argv[])
 
 	mining_threads = opt_n_threads + gpu_threads;
 
-	total_threads = mining_threads + 5;
+	total_threads = mining_threads + 7;
 	work_restart = calloc(total_threads, sizeof(*work_restart));
 	if (!work_restart)
 		quit(1, "Failed to calloc work_restart");
@@ -4050,11 +4066,9 @@ int main (int argc, char *argv[])
 		quit(0, "No pools active! Exiting.");
 
 #ifdef HAVE_OPENCL
-	i = 0;
-
 	/* start GPU mining threads */
-	for (j = 0; j < nDevs * opt_g_threads; j++) {
-		int gpu = j % nDevs;
+	for (i = 0; i < nDevs * opt_g_threads; i++) {
+		int gpu = i % nDevs;
 
 		gpus[gpu].is_gpu = 1;
 		gpus[gpu].cpu_gpu = gpu;
@@ -4087,8 +4101,6 @@ int main (int argc, char *argv[])
 
 		if (unlikely(thr_info_create(thr, NULL, gpuminer_thread, thr)))
 			quit(1, "thread %d create failed", i);
-
-		i++;
 	}
 
 	applog(LOG_INFO, "%d gpu miner threads started", gpu_threads);
@@ -4134,6 +4146,24 @@ int main (int argc, char *argv[])
 		quit(1, "input thread create failed");
 	pthread_detach(*thr->pth);
 
+	/* Create reinit cpu thread */
+	cpur_thr_id = mining_threads + 5;
+	thr = &thr_info[cpur_thr_id];
+	thr->q = tq_new();
+	if (!thr->q)
+		quit(1, "tq_new failed for cpur_thr_id");
+	if (thr_info_create(thr, NULL, reinit_cpu, thr))
+		quit(1, "reinit_cpu thread create failed");
+
+	/* Create reinit gpu thread */
+	gpur_thr_id = mining_threads + 6;
+	thr = &thr_info[gpur_thr_id];
+	thr->q = tq_new();
+	if (!thr->q)
+		quit(1, "tq_new failed for gpur_thr_id");
+	if (thr_info_create(thr, NULL, reinit_gpu, thr))
+		quit(1, "reinit_gpu thread create failed");
+
 	/* main loop - simply wait for workio thread to exit */
 	pthread_join(*thr_info[work_thr_id].pth, NULL);
 	applog(LOG_INFO, "workio thread dead, exiting.");