src/common/trace-chunk-registry.h

   1 /*
   2  * Copyright (C) 2019 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef LTTNG_TRACE_CHUNK_REGISTRY_H
   9 #define LTTNG_TRACE_CHUNK_REGISTRY_H
  10
  11 #include <stddef.h>
  12 #include <stdint.h>
  13 #include <stdbool.h>
  14 #include <common/macros.h>
  15 #include <common/trace-chunk.h>
  16
  17 struct lttng_trace_chunk_registry;
  18
  19 /*
  20  * Create an lttng_trace_chunk registry.
  21  *
  22  * A trace chunk registry maintains an association between a
  23  * (session_id, chunk_id) tuple and a trace chunk object. The chunk_id can
  24  * be "unset" in the case of an anonymous trace chunk.
  25  *
  26  * Note that a trace chunk registry holds no ownership of its trace
  27  * chunks. Trace chunks are unpublished when their last reference is released.
  28  * See the documentation of lttng_trace_chunk.
  29  *
  30  * Returns a trace chunk registry on success, NULL on error.
  31  *
  32  * Note that a trace chunk registry may only be accessed by an RCU thread.
  33  */
  34 struct lttng_trace_chunk_registry *lttng_trace_chunk_registry_create(void);
  35
  36 /*
  37  * Destroy an lttng trace chunk registry. The registry must be emptied
  38  * (i.e. all references to the trace chunks it contains must be released) before
  39  * it is destroyed.
  40  */
  41 void lttng_trace_chunk_registry_destroy(
  42                 struct lttng_trace_chunk_registry *registry);
  43
  44 /*
  45  * Publish a trace chunk for a given session id.
  46  * A reference is acquired on behalf of the caller.
  47  *
  48  * The trace chunk that is returned is the published version of the trace
  49  * chunk. The chunk provided should be discarded on success and it's
  50  * published version used in its place.
  51  *
  52  * See the documentation of lttng_trace_chunk for more information on
  53  * the usage of the various parameters.
  54  *
  55  * Returns an lttng_trace_chunk on success, NULL on error.
  56  */
  57 struct lttng_trace_chunk *lttng_trace_chunk_registry_publish_chunk(
  58                 struct lttng_trace_chunk_registry *registry,
  59                 uint64_t session_id, struct lttng_trace_chunk *chunk);
  60 /*
  61  * Adds the `previously_published` parameter which allows the caller
  62  * to know if a trace chunk equivalent to `chunk` was previously published.
  63  *
  64  * The registry holds a reference to the published trace chunks it contains.
  65  * Trace chunks automatically unpublish themselves from their registry on
  66  * destruction.
  67  *
  68  * This information is necessary to drop the reference of newly published
  69  * chunks when a user doesn't wish to explicitly maintain all references
  70  * to a given trace chunk.
  71  *
  72  * For instance, the relay daemon doesn't need the registry to hold a
  73  * reference since it controls the lifetime of its trace chunks.
  74  * Conversely, the consumer daemons rely on the session daemon to inform
  75  * them of the end of life of a trace chunk and the trace chunks don't
  76  * belong to a specific top-level object: they are always retrieved from
  77  * the registry by `id`.
  78  */
  79 struct lttng_trace_chunk *lttng_trace_chunk_registry_publish_chunk(
  80                 struct lttng_trace_chunk_registry *registry,
  81                 uint64_t session_id, struct lttng_trace_chunk *chunk,
  82                 bool *previously_published);
  83
  84 /*
  85  * Look-up a trace chunk by session_id and chunk_id.
  86  * A reference is acquired on behalf of the caller.
  87  *
  88  * Returns an lttng_trace_chunk on success, NULL if the chunk does not exist.
  89  */
  90 struct lttng_trace_chunk *
  91 lttng_trace_chunk_registry_find_chunk(
  92                 const struct lttng_trace_chunk_registry *registry,
  93                 uint64_t session_id, uint64_t chunk_id);
  94
  95 /*
  96  * Query the existence of a trace chunk by session_id and chunk_id.
  97  *
  98  * Returns 0 on success, a negative value on error.
  99  */
 100 int lttng_trace_chunk_registry_chunk_exists(
 101                 const struct lttng_trace_chunk_registry *registry,
 102                 uint64_t session_id, uint64_t chunk_id, bool *chunk_exists);
 103
 104 /*
 105  * Look-up an anonymous trace chunk by session_id.
 106  * A reference is acquired on behalf of the caller.
 107  *
 108  * Returns an lttng_trace_chunk on success, NULL if the chunk does not exist.
 109  */
 110 struct lttng_trace_chunk *
 111 lttng_trace_chunk_registry_find_anonymous_chunk(
 112                 const struct lttng_trace_chunk_registry *registry,
 113                 uint64_t session_id);
 114
 115 unsigned int lttng_trace_chunk_registry_put_each_chunk(
 116                 const struct lttng_trace_chunk_registry *registry);
 117
 118 #endif /* LTTNG_TRACE_CHUNK_REGISTRY_H */