From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 30 May 2018 00:28:01 +0000 (+0200)
Subject: ustctl: Implement ring buffer clear
X-Git-Tag: v2.12.0-rc1~25
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=beca55a1aa4ff272188d7c37c19eb0540f811c8b;p=lttng-ust.git

ustctl: Implement ring buffer clear

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/include/lttng/ust-ctl.h b/include/lttng/ust-ctl.h
index 3404d9c7..932940ba 100644
--- a/include/lttng/ust-ctl.h
+++ b/include/lttng/ust-ctl.h
@@ -242,6 +242,7 @@ int ustctl_put_subbuf(struct ustctl_consumer_stream *stream);
 
 void ustctl_flush_buffer(struct ustctl_consumer_stream *stream,
 		int producer_active);
+void ustctl_clear_buffer(struct ustctl_consumer_stream *stream);
 
 /* index */
 
diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index 8c38ffaf..949ece17 100644
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -1590,6 +1590,19 @@ void ustctl_flush_buffer(struct ustctl_consumer_stream *stream,
 		consumer_chan->chan->handle);
 }
 
+void ustctl_clear_buffer(struct ustctl_consumer_stream *stream)
+{
+	struct lttng_ust_lib_ring_buffer *buf;
+	struct ustctl_consumer_channel *consumer_chan;
+
+	assert(stream);
+	buf = stream->buf;
+	consumer_chan = stream->chan;
+	lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE,
+		consumer_chan->chan->handle);
+	lib_ring_buffer_clear_reader(buf, consumer_chan->chan->handle);
+}
+
 static
 struct lttng_ust_client_lib_ring_buffer_client_cb *get_client_cb(
 		struct lttng_ust_lib_ring_buffer *buf,
diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h
index 323a8df7..4ad921ec 100644
--- a/libringbuffer/frontend_internal.h
+++ b/libringbuffer/frontend_internal.h
@@ -205,6 +205,32 @@ void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf,
 					      consumed_new) != consumed_old));
 }
 
+static inline
+void lib_ring_buffer_clear_reader(struct lttng_ust_lib_ring_buffer *buf,
+				  struct lttng_ust_shm_handle *handle)
+{
+	struct channel *chan;
+	const struct lttng_ust_lib_ring_buffer_config *config;
+	unsigned long offset, consumed_old, consumed_new;
+
+	chan = shmp(handle, buf->backend.chan);
+	if (!chan)
+		return;
+	config = &chan->backend.config;
+
+	do {
+		offset = v_read(config, &buf->offset);
+		consumed_old = uatomic_read(&buf->consumed);
+		if (caa_unlikely(subbuf_trunc(offset, chan)
+			      - subbuf_trunc(consumed_old, chan)
+			     > 0))
+			consumed_new = subbuf_trunc(offset, chan);
+		else
+			return;
+	} while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,
+					      consumed_new) != consumed_old));
+}
+
 static inline
 int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config,
 				 struct lttng_ust_lib_ring_buffer *buf,