From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 4 Feb 2020 20:44:55 +0000 (-0500)
Subject: lib ring buffer iterator: introduce lib_ring_buffer_put_current_record
X-Git-Tag: v2.13.0-rc1~146
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=47d4b31dc9703024784af6af0a906d9458f648bf;p=lttng-modules.git

lib ring buffer iterator: introduce lib_ring_buffer_put_current_record

Ensure that the current subbuffer is put after client code has read the
payload of the current record.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id2173ea67213f7ef8e7395b49c5aa8fff0aefffc
---

diff --git a/include/ringbuffer/iterator.h b/include/ringbuffer/iterator.h
index a006ed00..a9879903 100644
--- a/include/ringbuffer/iterator.h
+++ b/include/ringbuffer/iterator.h
@@ -23,6 +23,15 @@
 extern ssize_t lib_ring_buffer_get_next_record(struct channel *chan,
 					       struct lib_ring_buffer *buf);
 
+/*
+ * Ensure that the current subbuffer is put after client code has read the
+ * payload of the current record. Has an effect when the end of subbuffer is
+ * reached. It is not required if get_next_record is called successively.
+ * However, it should be invoked before returning data to user-space to ensure
+ * that the get/put subbuffer state is quiescent.
+ */
+extern void lib_ring_buffer_put_current_record(struct lib_ring_buffer *buf);
+
 /*
  * channel_get_next_record advances the buffer read position to the next record.
  * It returns either the size of the next record, -EAGAIN if there is currently
diff --git a/src/lib/ringbuffer/ring_buffer_iterator.c b/src/lib/ringbuffer/ring_buffer_iterator.c
index a136a8fa..da19d280 100644
--- a/src/lib/ringbuffer/ring_buffer_iterator.c
+++ b/src/lib/ringbuffer/ring_buffer_iterator.c
@@ -105,6 +105,24 @@ restart:
 }
 EXPORT_SYMBOL_GPL(lib_ring_buffer_get_next_record);
 
+void lib_ring_buffer_put_current_record(struct lib_ring_buffer *buf)
+{
+	struct lib_ring_buffer_iter *iter;
+
+	if (!buf)
+		return;
+	iter = &buf->iter;
+	if (iter->state != ITER_NEXT_RECORD)
+		return;
+	iter->read_offset += iter->payload_len;
+	iter->state = ITER_TEST_RECORD;
+	if (iter->read_offset - iter->consumed >= iter->data_size) {
+		lib_ring_buffer_put_next_subbuf(buf);
+		iter->state = ITER_GET_SUBBUF;
+	}
+}
+EXPORT_SYMBOL_GPL(lib_ring_buffer_put_current_record);
+
 static int buf_is_higher(void *a, void *b)
 {
 	struct lib_ring_buffer *bufa = a;
@@ -696,12 +714,14 @@ skip_get_next:
 			return -EFAULT;
 		}
 		read_count += copy_len;
-	};
-	return read_count;
+	}
+	goto put_record;
 
 nodata:
 	*ppos = 0;
 	chan->iter.len_left = 0;
+put_record:
+	lib_ring_buffer_put_current_record(buf);
 	return read_count;
 }