diff --git a/include/villas/nodes/shmem.h b/include/villas/nodes/shmem.h
index de66ff2c8..b56e3afee 100644
--- a/include/villas/nodes/shmem.h
+++ b/include/villas/nodes/shmem.h
@@ -5,22 +5,19 @@
 #include "memory.h"
 #include "pool.h"
 #include "queue.h"
+#include "queue_signalled.h"
 
 #define DEFAULT_SHMEM_QUEUESIZE 512
 
-/** Per-direction shared datastructure for a shmem node. */
-struct shmem_queue {
-	struct queue queue; /**< Actual queue where the samples are passed */
-	pthread_cond_t ready; /**< Condition variable to signal writes to the queue */
-	pthread_condattr_t readyattr;
-	pthread_mutex_t mt; /**< Mutex for ready */
-	pthread_mutexattr_t mtattr;
+union shmem_queue {
+	struct queue q;
+	struct queue_signalled qs;
 };
 
 /** The structure that actually resides in the shared memory. TODO better name?*/
 struct shmem_shared {
-	struct shmem_queue in; /**< Queue for samples passed from external program to node.*/
-	struct shmem_queue out; /**< Queue for samples passed from node to external program.*/
+	union shmem_queue in; /**< Queue for samples passed from external program to node.*/
+	union shmem_queue out; /**< Queue for samples passed from node to external program.*/
 	struct pool pool; /**< Pool for the samples in the queues. */
 };
 
diff --git a/include/villas/queue_signalled.h b/include/villas/queue_signalled.h
new file mode 100644
index 000000000..84acb8909
--- /dev/null
+++ b/include/villas/queue_signalled.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <pthread.h>
+
+#include "queue.h"
+
+/** Wrapper around queue that uses POSIX CV's for signalling writes. */
+struct queue_signalled {
+	struct queue q; /**< Actual underlying queue. */
+	pthread_cond_t ready; /**< Condition variable to signal writes to the queue. */
+	pthread_condattr_t readyattr;
+	pthread_mutex_t mt; /**< Mutex for ready. */
+	pthread_mutexattr_t mtattr;
+};
+
+int queue_signalled_init(struct queue_signalled *qs, size_t size, struct memtype *mem);
+
+int queue_signalled_destroy(struct queue_signalled *qs);
+
+int queue_signalled_push_many(struct queue_signalled *qs, void *ptr[], size_t cnt);
+
+int queue_signalled_pull_many(struct queue_signalled *qs, void *ptr[], size_t cnt);
diff --git a/lib/Makefile.inc b/lib/Makefile.inc
index 7eeaa9935..b20543b9e 100644
--- a/lib/Makefile.inc
+++ b/lib/Makefile.inc
@@ -8,7 +8,7 @@ LIB_SRCS = $(addprefix lib/nodes/, file.c cbuilder.c shmem.c) 		\
            $(addprefix lib/kernel/, kernel.c rt.c)		\
            $(addprefix lib/, sample.c path.c node.c hook.c	\
               log.c utils.c super_node.c hist.c timing.c pool.c	\
-              list.c queue.c memory.c advio.c web.c api.c	\
+              list.c queue.c queue_signalled.c memory.c advio.c web.c api.c	\
               plugin.c node_type.c stats.c mapping.c sample_io.c\
            )
 
diff --git a/lib/nodes/shmem.c b/lib/nodes/shmem.c
index c3a777ebd..7444b2f02 100644
--- a/lib/nodes/shmem.c
+++ b/lib/nodes/shmem.c
@@ -31,16 +31,6 @@ int shmem_parse(struct node *n, config_setting_t *cfg) {
 	return 0;
 }
 
-/* Helper for initializing condition variables / mutexes. */
-void shmem_cond_init(struct shmem_queue *queue) {
-	pthread_mutexattr_init(&queue->mtattr);
-	pthread_mutexattr_setpshared(&queue->mtattr, PTHREAD_PROCESS_SHARED);
-	pthread_condattr_init(&queue->readyattr);
-	pthread_condattr_setpshared(&queue->readyattr, PTHREAD_PROCESS_SHARED);
-	pthread_mutex_init(&queue->mt, &queue->mtattr);
-	pthread_cond_init(&queue->ready, &queue->readyattr);
-}
-
 int shmem_open(struct node *n) {
 	struct shmem *shm = n->_vd;
 
@@ -63,24 +53,36 @@ int shmem_open(struct node *n) {
 	if (!shm->shared)
 		error("Shm shared struct allocation failed (not enough memory?)");
 	memset(shm->shared, 0, sizeof(struct shmem_shared));
-	if (queue_init(&shm->shared->in.queue, shm->insize, shm->manager) < 0)
-		error("Shm queue allocation failed (not enough memory?)");
-	if (queue_init(&shm->shared->out.queue, shm->outsize, shm->manager) < 0)
-		error("Shm queue allocation failed (not enough memory?)");
+	if (shm->cond_in) {
+		if (queue_signalled_init(&shm->shared->in.qs, shm->insize, shm->manager) < 0)
+			error("Shm queue allocation failed (not enough memory?)");
+	} else {
+		if (queue_init(&shm->shared->in.q, shm->insize, shm->manager) < 0)
+			error("Shm queue allocation failed (not enough memory?)");
+	}
+	if (shm->cond_out) {
+		if (queue_signalled_init(&shm->shared->out.qs, shm->outsize, shm->manager) < 0)
+			error("Shm queue allocation failed (not enough memory?)");
+	} else {
+		if (queue_init(&shm->shared->out.q, shm->outsize, shm->manager) < 0)
+			error("Shm queue allocation failed (not enough memory?)");
+	}
 	if (pool_init(&shm->shared->pool, shm->insize+shm->outsize, SAMPLE_LEN(shm->sample_size), shm->manager) < 0)
 		error("Shm pool allocation failed (not enough memory?)");
-	if (shm->cond_out)
-		shmem_cond_init(&shm->shared->out);
-	if (shm->cond_in)
-		shmem_cond_init(&shm->shared->in);
 
 	return 0;
 }
 
 int shmem_close(struct node *n) {
 	struct shmem* shm = n->_vd;
-	queue_destroy(&shm->shared->in.queue);
-	queue_destroy(&shm->shared->out.queue);
+	if (shm->cond_in)
+		queue_signalled_destroy(&shm->shared->in.qs);
+	else
+		queue_destroy(&shm->shared->in.q);
+	if (shm->cond_out)
+		queue_signalled_destroy(&shm->shared->out.qs);
+	else
+		queue_destroy(&shm->shared->out.q);
 	pool_destroy(&shm->shared->pool);
 	int r = munmap(shm->base, shm->len);
 	if (r != 0)
@@ -90,13 +92,9 @@ int shmem_close(struct node *n) {
 
 int shmem_read(struct node *n, struct sample *smps[], unsigned cnt) {
 	struct shmem *shm = n->_vd;
-	if (shm->cond_in) {
-		pthread_mutex_lock(&shm->shared->in.mt);
-		pthread_cond_wait(&shm->shared->in.ready, &shm->shared->in.mt);
-		pthread_mutex_unlock(&shm->shared->in.mt);
-	}
-	int r = queue_pull_many(&shm->shared->in.queue, (void**) smps, cnt);
-	return r;
+	if (shm->cond_in)
+		return queue_signalled_pull_many(&shm->shared->in.qs, (void**) smps, cnt);
+	return queue_pull_many(&shm->shared->in.q, (void**) smps, cnt);
 }
 
 int shmem_write(struct node *n, struct sample *smps[], unsigned cnt) {
@@ -119,14 +117,13 @@ int shmem_write(struct node *n, struct sample *smps[], unsigned cnt) {
 		shared_smps[i]->length = len;
 		sample_get(shared_smps[i]);
 	}
-	int pushed = queue_push_many(&shm->shared->out.queue, (void**) shared_smps, avail);
+	int pushed;
+	if (shm->cond_out)
+		pushed = queue_signalled_push_many(&shm->shared->out.qs, (void**) shared_smps, avail);
+	else
+		pushed = queue_push_many(&shm->shared->out.q, (void**) shared_smps, avail);
 	if (pushed != avail)
 		warn("Outqueue overrun for shmem node %s", shm->name);
-	if (pushed && shm->cond_out) {
-		pthread_mutex_lock(&shm->shared->out.mt);
-		pthread_cond_broadcast(&shm->shared->out.ready);
-		pthread_mutex_unlock(&shm->shared->out.mt);
-	}
 	return pushed;
 }
 
diff --git a/lib/queue_signalled.c b/lib/queue_signalled.c
new file mode 100644
index 000000000..71ae87d21
--- /dev/null
+++ b/lib/queue_signalled.c
@@ -0,0 +1,46 @@
+/** Wrapper around queue that uses POSIX CV's for signalling writes. */
+
+#include "queue_signalled.h"
+
+int queue_signalled_init(struct queue_signalled *qs, size_t size, struct memtype *mem)
+{
+	int r = queue_init(&qs->q, size, mem);
+	if (r < 0)
+		return r;
+	pthread_mutexattr_init(&qs->mtattr);
+	pthread_mutexattr_setpshared(&qs->mtattr, PTHREAD_PROCESS_SHARED);
+	pthread_condattr_init(&qs->readyattr);
+	pthread_condattr_setpshared(&qs->readyattr, PTHREAD_PROCESS_SHARED);
+	pthread_mutex_init(&qs->mt, &qs->mtattr);
+	pthread_cond_init(&qs->ready, &qs->readyattr);
+	return 0;
+}
+
+int queue_signalled_destroy(struct queue_signalled *qs)
+{
+	int r = queue_destroy(&qs->q);
+	if (r < 0)
+		return r;
+	pthread_cond_destroy(&qs->ready);
+	pthread_mutex_destroy(&qs->mt);
+	return 0;
+}
+
+int queue_signalled_push_many(struct queue_signalled *qs, void *ptr[], size_t cnt)
+{
+	int r = queue_push_many(&qs->q, ptr, cnt);
+	if (r > 0) {
+		pthread_mutex_lock(&qs->mt);
+		pthread_cond_broadcast(&qs->ready);
+		pthread_mutex_unlock(&qs->mt);
+	}
+	return r;
+}
+
+int queue_signalled_pull_many(struct queue_signalled *qs, void *ptr[], size_t cnt)
+{
+	pthread_mutex_lock(&qs->mt);
+	pthread_cond_wait(&qs->ready, &qs->mt);
+	pthread_mutex_unlock(&qs->mt);
+	return queue_pull_many(&qs->q, ptr, cnt);
+}
diff --git a/src/shmem.c b/src/shmem.c
index 1f29b2a45..0d55fdc72 100644
--- a/src/shmem.c
+++ b/src/shmem.c
@@ -45,12 +45,11 @@ int main(int argc, char* argv[])
 
 	struct sample *insmps[node->vectorize], *outsmps[node->vectorize];
 	while (1) {
-		if (shm->cond_out) {
-			pthread_mutex_lock(&shmem->out.mt);
-			pthread_cond_wait(&shmem->out.ready, &shmem->out.mt);
-			pthread_mutex_unlock(&shmem->out.mt);
-		}
-		int r = queue_pull_many(&shmem->out.queue, (void **) insmps, node->vectorize);
+		int r, w;
+		if (shm->cond_out)
+			r = queue_signalled_pull_many(&shmem->out.qs, (void **) insmps, node->vectorize);
+		else
+			r = queue_pull_many(&shmem->out.q, (void **) insmps, node->vectorize);
 		int avail = sample_alloc(&shmem->pool, outsmps, r);
 		if (avail < r)
 			warn("pool underrun (%d/%d)\n", avail, r);
@@ -65,13 +64,11 @@ int main(int argc, char* argv[])
 		}
 		for (int i = 0; i < r; i++)
 			sample_put(insmps[i]);
-		int w = queue_push_many(&shmem->in.queue, (void **) outsmps, avail);
+		if (shm->cond_in)
+			w = queue_signalled_push_many(&shmem->in.qs, (void **) outsmps, avail);
+		else
+			w = queue_push_many(&shmem->in.q, (void **) outsmps, avail);
 		if (w < avail)
 			warn("short write (%d/%d)\n", w, r);
-		if (shm->cond_in && w) {
-			pthread_mutex_lock(&shmem->in.mt);
-			pthread_cond_broadcast(&shmem->in.ready);
-			pthread_mutex_unlock(&shmem->in.mt);
-		}
 	}
 }