Fix: wrapper random documentation

[lttng-modules.git] / lib / ringbuffer / frontend_internal.h

diff --git a/lib/ringbuffer/frontend_internal.h b/lib/ringbuffer/frontend_internal.h
index 88820f7e5c0c04d6b66255e38524c59b760e70a2..39f2b7701783c4b57b6ce1a6cd0c6028263b5323 100644 (file)
--- a/lib/ringbuffer/frontend_internal.h
+++ b/lib/ringbuffer/frontend_internal.h
@@ -1,33 +1,17 @@
-#ifndef _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
-#define _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
-
-/*
+/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
+ *
  * linux/ringbuffer/frontend_internal.h
  *
  * Ring Buffer Library Synchronization Header (internal helpers).
  *
  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; only
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- *
- * Author:
- *     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
  * See ring_buffer_frontend.c for more information on wait-free algorithms.
  */
 
+#ifndef _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
+#define _LIB_RING_BUFFER_FRONTEND_INTERNAL_H
+
 #include <wrapper/ringbuffer/config.h>
 #include <wrapper/ringbuffer/backend_types.h>
 #include <wrapper/ringbuffer/frontend_types.h>
@@ -150,7 +134,8 @@ int last_tsc_overflow(const struct lib_ring_buffer_config *config,
 #endif
 
 extern
-int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx);
+int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx,
+               void *client_ctx);
 
 extern
 void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf,
@@ -167,9 +152,10 @@ void lib_ring_buffer_check_deliver_slow(const struct lib_ring_buffer_config *con
 
 extern
 void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf);
-
 extern
 void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf);
+extern
+void lib_ring_buffer_clear(struct lib_ring_buffer *buf);
 
 /* Buffer write helpers */
 
@@ -201,6 +187,33 @@ void lib_ring_buffer_reserve_push_reader(struct lib_ring_buffer *buf,
                                              consumed_new) != consumed_old));
 }
 
+/*
+ * Move consumed position to the beginning of subbuffer in which the
+ * write offset is. Should only be used on ring buffers that are not
+ * actively being written into, because clear_reader does not take into
+ * account the commit counters when moving the consumed position, which
+ * can make concurrent trace producers or consumers observe consumed
+ * position further than the write offset, which breaks ring buffer
+ * algorithm guarantees.
+ */
+static inline
+void lib_ring_buffer_clear_reader(struct lib_ring_buffer *buf,
+                                 struct channel *chan)
+{
+       const struct lib_ring_buffer_config *config = &chan->backend.config;
+       unsigned long offset, consumed_old, consumed_new;
+
+       do {
+               offset = v_read(config, &buf->offset);
+               consumed_old = atomic_long_read(&buf->consumed);
+               CHAN_WARN_ON(chan, (long) (subbuf_trunc(offset, chan)
+                               - subbuf_trunc(consumed_old, chan))
+                               < 0);
+               consumed_new = subbuf_trunc(offset, chan);
+       } while (unlikely(atomic_long_cmpxchg(&buf->consumed, consumed_old,
+                                             consumed_new) != consumed_old));
+}
+
 static inline
 int lib_ring_buffer_pending_data(const struct lib_ring_buffer_config *config,
                                 struct lib_ring_buffer *buf,