diff --git a/chan.c b/chan.c
index 68f0e00..800cd0c 100644
--- a/chan.c
+++ b/chan.c
@@ -57,10 +57,13 @@ int hip_chan_send(hip_chan_t* c, const void* ptr, hip_oow_t len)
 	hip = c->hip;
 	caller = UCTX_FROM_LINK(hip->running);
 
-	if (c->unit_count < c->unit_capa)
+	if (HIP_LIST_IS_EMPTY(&c->recvq))
 	{
-		/* buffered */
 		hip_uint8_t* dptr;
+
+		if (c->unit_count >= c->unit_capa) goto block;
+
+		/* the buffer is not full. write to the buffer */
 		if (len > c->unit_size) len = c->unit_size; /* can't buffer longer than the specified unit size */
 		dptr = &c->buf[c->unit_wpos * c->unit_size];
 		memcpy(dptr, ptr, len);
@@ -71,10 +74,16 @@ int hip_chan_send(hip_chan_t* c, const void* ptr, hip_oow_t len)
 		}
 		c->unit_wpos = (c->unit_wpos + 1) % c->unit_capa;
 		c->unit_count++;
+
+		/* give another routine a chance to read.
+		 * does this cause too many context switches?
+		 * without this, there is a high chance the the same routine
+		 * starves the channel by reading and writing in succession
+		 * if it read and write on the same channel */
+		hip_yield(hip);
 		return len;
 	}
-
-	if (!HIP_LIST_IS_EMPTY(&c->recvq)) /* there is a receving routine */
+	else /* there is a receiving routing waiting */
 	{
 		hip_uctx_link_t* x;
 		hip_uctx_t* recver;
@@ -95,6 +104,7 @@ int hip_chan_send(hip_chan_t* c, const void* ptr, hip_oow_t len)
 	}
 
 
+block:
 	/* remember the data holder and places the current running routine in the send queue */
 	caller->chan_data_ptr = (hip_uint8_t*)ptr;
 	caller->chan_data_len = len;
@@ -115,16 +125,22 @@ int hip_chan_recv(hip_chan_t* c, void* ptr, hip_oow_t len)
 	hip = c->hip;
 	caller = UCTX_FROM_LINK(hip->running);
 
-	if (c->unit_count > 0)
+	if (HIP_LIST_IS_EMPTY(&c->sendq))
 	{
+		if (c->unit_count <= 0) goto block;
+
+		/* the buffer is not empty. there's data to read */
 		if (len > c->unit_size) len = c->unit_size;
 		memcpy(ptr, &c->buf[c->unit_rpos * c->unit_size], len);
 		c->unit_rpos = (c->unit_rpos + 1) % c->unit_capa;
 		c->unit_count--;
+
+		/* In receiving, i doubt it causes starvation to not yield to another routine.
+		 * let me not switch to the scheduler here for now. */
+		/*hip_yield(hip);*/
 		return len;
 	}
-
-	if (!HIP_LIST_IS_EMPTY(&c->sendq)) /* there is a sending routine */
+	else /* there is a sending routine */
 	{
 		hip_uctx_link_t* x;
 		hip_uctx_t* sener;
@@ -145,6 +161,7 @@ int hip_chan_recv(hip_chan_t* c, void* ptr, hip_oow_t len)
 		return len;
 	}
 
+block:
 	/* remember the data holder and place the calling routine in the receive queue */
 	caller->chan_data_ptr = ptr;
 	caller->chan_data_len = len;
diff --git a/ctx.c b/ctx.c
index 873ffe0..01cd5ba 100644
--- a/ctx.c
+++ b/ctx.c
@@ -828,7 +828,7 @@ int main()
 
 setbuf(stdout, NULL);
 	hip = hip_open(HIP_FLAG_LAZY);
-	chan = hip_chan_open(hip, 100, 0);
+	chan = hip_chan_open(hip, 100, 1);
 
 	hip_newrtn(hip, 0, uf1, chan);
 	hip_newrtn(hip, 0, uf2, HIP_NULL);