0001-staprun-print-flush.patch

From ecda3a46517357d190c8978b502dac1a1cb45ab0 Mon Sep 17 00:00:00 2001
From: Sultan Alsawaf <sultan@openresty.com>
Date: Thu, 21 Jan 2021 13:52:46 -0800
Subject: [PATCH] staprun print flush

---
 runtime/transport/control.c        | 12 ++++++++++++
 runtime/transport/relay_v2.c       | 24 +++++++++++++++++++++---
 runtime/transport/transport_msgs.h |  3 +++
 staprun/common.c                   |  3 ++-
 staprun/relay.c                    |  3 +++
 5 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/runtime/transport/control.c b/runtime/transport/control.c
index d123bef2f..7f420a7f5 100644
--- a/runtime/transport/control.c
+++ b/runtime/transport/control.c
@@ -52,6 +52,18 @@ static ssize_t _stp_ctl_write_cmd(struct file *file, const char __user *buf, siz
 	if (get_user(type, (u32 __user *)buf))
 		return -EFAULT;
 
+	/* Swap the subbuf without potentially sleeping on _cmd_mutex */
+	if (type == STP_RELAY_SWITCH_SUBBUF) {
+		unsigned long flags;
+
+		/* This will only fail after the print driver is destroyed */
+		if (_stp_print_trylock_irqsave(&flags)) {
+			_stp_switch_current_subbuf();
+			_stp_print_unlock_irqrestore(&flags);
+		}
+		return count;
+	}
+
 	count -= sizeof(u32);
 	buf += sizeof(u32);
 
diff --git a/runtime/transport/relay_v2.c b/runtime/transport/relay_v2.c
index 27729f4c8..4ee260888 100644
--- a/runtime/transport/relay_v2.c
+++ b/runtime/transport/relay_v2.c
@@ -323,10 +323,12 @@ _stp_data_write_reserve(size_t size_request, void **entry)
 
 	buf = _stp_get_rchan_subbuf(_stp_relay_data.rchan->buf,
 				    smp_processor_id());
-	if (unlikely(buf->offset + size_request > buf->chan->subbuf_size)) {
+	if (buf->offset >= buf->chan->subbuf_size) {
 		size_request = __stp_relay_switch_subbuf(buf, size_request);
 		if (!size_request)
 			return 0;
+	} else if (buf->offset + size_request > buf->chan->subbuf_size) {
+		size_request = buf->chan->subbuf_size - buf->offset;
 	}
 	*entry = (char*)buf->data + buf->offset;
 	buf->offset += size_request;
@@ -344,8 +346,24 @@ static int _stp_data_write_commit(void *entry)
 {
 	struct rchan_buf *buf;
 
+	/*
+	 * For the case of a single partially filled subbuf, we must flush it in
+	 * order for relay to wake the reader.
+	 */
 	buf = _stp_get_rchan_subbuf(_stp_relay_data.rchan->buf,
-				    smp_processor_id());
-	__stp_relay_switch_subbuf(buf, 0);
+				    raw_smp_processor_id());
+	if (buf->subbufs_produced == buf->subbufs_consumed)
+		__stp_relay_switch_subbuf(buf, 0);
 	return 0;
 }
+
+static void _stp_switch_current_subbuf(void)
+{
+	struct rchan_buf *buf;
+
+	/* Switch the current subbuf if it has data so staprun can read it */
+	buf = _stp_get_rchan_subbuf(_stp_relay_data.rchan->buf,
+				    raw_smp_processor_id());
+	if (buf->offset)
+		__stp_relay_switch_subbuf(buf, 0);
+}
diff --git a/runtime/transport/transport_msgs.h b/runtime/transport/transport_msgs.h
index 9e0081c80..85f8db56f 100644
--- a/runtime/transport/transport_msgs.h
+++ b/runtime/transport/transport_msgs.h
@@ -87,6 +87,9 @@ enum
 	/** Send by staprun to notify module of remote identity, if any.
             Only send once at startup.  */
         STP_REMOTE_ID,
+	/** Send by staprun to make module switch the current CPU's print
+            subbuf out for reading if there's data in it.  */
+	STP_RELAY_SWITCH_SUBBUF,
 	/** Max number of message types, sanity check only.  */
 	STP_MAX_CMD,
   /** Sent by stapio after having recevied STP_TRANSPORT. Notifies
diff --git a/staprun/common.c b/staprun/common.c
index 6a603cd2b..b8861106b 100644
--- a/staprun/common.c
+++ b/staprun/common.c
@@ -668,7 +668,8 @@ int send_request(int type, void *data, int len)
 		return -1;
 	}
 	memcpy(buf, &type, sizeof (type));
-	memcpy(&buf[sizeof (type)], data, len);
+	if (len)
+		memcpy(&buf[sizeof (type)], data, len);
 
 	errno = 0;
         assert (control_channel >= 0);
diff --git a/staprun/relay.c b/staprun/relay.c
index d0202e52f..8d933e0df 100644
--- a/staprun/relay.c
+++ b/staprun/relay.c
@@ -188,6 +188,9 @@ static void *reader_thread(void *data)
 			}
                 }
 
+		/* Switch out the current subbuf if it has data */
+		send_request(STP_RELAY_SWITCH_SUBBUF, NULL, 0);
+
 		while ((rc = read(relay_fd[cpu], buf, sizeof(buf))) > 0) {
                         int wbytes = rc;
                         char *wbuf = buf;
-- 
2.30.0