From 3e9d0dfe1d9bdb0ea305b9dc0cd66400c90a0dd8 Mon Sep 17 00:00:00 2001
From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Date: Fri, 8 Feb 2019 17:05:10 -0500
Subject: [PATCH] Consumer: Implement lttng_consumer_clear_channel

This function is responsible for performing all actions needed to
clear a given channel.

It only supports clear operation on unmonitored channel
(snapshot mode) for now.

To do so, flush and clear all the channel streams.

We use an active flush (consumer_flush_buffer(..., 1)) since we consider
the producer active at all time. No reason so far to check for the
quiescent state of the channel. This might need to be revisited.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
---
 src/common/consumer/consumer.c | 104 +++++++++++++++++++++++++++++++++
 src/common/consumer/consumer.h |   1 +
 2 files changed, 105 insertions(+)

diff --git a/src/common/consumer/consumer.c b/src/common/consumer/consumer.c
index 5772b9127..da81f2eed 100644
--- a/src/common/consumer/consumer.c
+++ b/src/common/consumer/consumer.c
@@ -3894,6 +3894,31 @@ end:
 	return ret;
 }
 
+static
+int consumer_clear_buffer(struct lttng_consumer_stream *stream)
+{
+	int ret = 0;
+
+	switch (consumer_data.type) {
+	case LTTNG_CONSUMER_KERNEL:
+		ret = kernctl_buffer_clear(stream->wait_fd);
+		if (ret < 0) {
+			ERR("Failed to flush kernel stream");
+			goto end;
+		}
+		break;
+	case LTTNG_CONSUMER32_UST:
+	case LTTNG_CONSUMER64_UST:
+		lttng_ustconsumer_clear_buffer(stream);
+		break;
+	default:
+		ERR("Unknown consumer_data type");
+		abort();
+	}
+
+end:
+	return ret;
+}
 /*
  * Sample the rotate position for all the streams of a channel. If a stream
  * is already at the rotate position (produced == consumed), we flag it as
@@ -4473,3 +4498,82 @@ int lttng_consumer_mkdir(const char *path, uid_t uid, gid_t gid,
 		return mkdir_local(path, uid, gid);
 	}
 }
+
+static
+int clear_unmonitored_channel(struct lttng_consumer_channel *channel)
+{
+
+	int ret;
+	struct lttng_consumer_stream *stream;
+
+	assert(!channel->monitor);
+	assert(channel->type != CONSUMER_CHANNEL_TYPE_METADATA);
+
+	rcu_read_lock();
+	pthread_mutex_lock(&channel->lock);
+	cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+		health_code_update();
+		pthread_mutex_lock(&stream->lock);
+
+		ret = consumer_flush_buffer(stream, 1);
+		if (ret < 0) {
+			ERR("Failed to flush stream %" PRIu64 " during channel clear",
+					stream->key);
+			ret = LTTCOMM_CONSUMERD_FATAL;
+			goto error_unlock;
+		}
+
+		ret = consumer_clear_buffer(stream);
+		if (ret < 0) {
+			ERR("Failed to clear stream %" PRIu64 " during channel clear",
+					stream->key);
+			ret = LTTCOMM_CONSUMERD_FATAL;
+			goto error_unlock;
+		}
+		pthread_mutex_unlock(&stream->lock);
+	}
+	pthread_mutex_unlock(&channel->lock);
+	rcu_read_unlock();
+	return 0;
+
+error_unlock:
+	pthread_mutex_unlock(&stream->lock);
+	pthread_mutex_unlock(&channel->lock);
+	rcu_read_unlock();
+	return ret;
+}
+
+int lttng_consumer_clear_channel(struct lttng_consumer_channel *channel)
+{
+	int ret;
+
+	DBG("Consumer clear channel %" PRIu64, channel->key);
+
+	if (!channel->monitor) {
+		/* Snapshot mode */
+		if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA) {
+			/*
+			 * Nothing to do for the metadata channel/stream.
+			 * Snapshot mechanism already take care of the metadata
+			 * handling/generation.
+			 */
+			goto end;
+		}
+		ret = clear_unmonitored_channel(channel);
+		if (ret) {
+			goto error;
+		}
+	} else {
+		/* TODO:
+		 * Normal channel and relayd bound clear operation not supported
+		 * for now
+		 */
+		ret = LTTCOMM_CONSUMERD_FATAL;
+		goto error;
+	}
+
+end:
+	ret = LTTCOMM_CONSUMERD_SUCCESS;
+error:
+	return ret;
+}
diff --git a/src/common/consumer/consumer.h b/src/common/consumer/consumer.h
index a90b3a385..0195e6884 100644
--- a/src/common/consumer/consumer.h
+++ b/src/common/consumer/consumer.h
@@ -853,5 +853,6 @@ void lttng_consumer_reset_stream_rotate_state(struct lttng_consumer_stream *stre
 int lttng_consumer_mkdir(const char *path, uid_t uid, gid_t gid,
 		uint64_t relayd_id);
 void lttng_consumer_cleanup_relayd(struct consumer_relayd_sock_pair *relayd);
+int lttng_consumer_clear_channel(struct lttng_consumer_channel *channel);
 
 #endif /* LIB_CONSUMER_H */
-- 
2.34.1