src/bin/lttng-relayd/ctf-trace.cpp

   1 /*
   2  * Copyright (C) 2013 Julien Desfossez <jdesfossez@efficios.com>
   3  * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
   4  * Copyright (C) 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * SPDX-License-Identifier: GPL-2.0-only
   7  *
   8  */
   9
  10 #define _LGPL_SOURCE
  11
  12 #include <common/common.hpp>
  13 #include <common/utils.hpp>
  14 #include <urcu/rculist.h>
  15
  16 #include "ctf-trace.hpp"
  17 #include "lttng-relayd.hpp"
  18 #include "stream.hpp"
  19
  20 static uint64_t last_relay_ctf_trace_id;
  21 static pthread_mutex_t last_relay_ctf_trace_id_lock = PTHREAD_MUTEX_INITIALIZER;
  22
  23 static void rcu_destroy_ctf_trace(struct rcu_head *rcu_head)
  24 {
  25         struct ctf_trace *trace =
  26                 caa_container_of(rcu_head, struct ctf_trace, rcu_node);
  27
  28         free(trace);
  29 }
  30
  31 /*
  32  * Destroy a ctf trace and all stream contained in it.
  33  *
  34  * MUST be called with the RCU read side lock.
  35  */
  36 static void ctf_trace_destroy(struct ctf_trace *trace)
  37 {
  38         /*
  39          * Getting to this point, every stream referenced by that trace
  40          * have put back their ref since the've been closed by the
  41          * control side.
  42          */
  43         LTTNG_ASSERT(cds_list_empty(&trace->stream_list));
  44         ASSERT_RCU_READ_LOCKED();
  45
  46         session_put(trace->session);
  47         trace->session = NULL;
  48         free(trace->path);
  49         trace->path = NULL;
  50         call_rcu(&trace->rcu_node, rcu_destroy_ctf_trace);
  51 }
  52
  53 static void ctf_trace_release(struct urcu_ref *ref)
  54 {
  55         struct ctf_trace *trace =
  56                 caa_container_of(ref, struct ctf_trace, ref);
  57         int ret;
  58         struct lttng_ht_iter iter;
  59
  60         iter.iter.node = &trace->node.node;
  61         ret = lttng_ht_del(trace->session->ctf_traces_ht, &iter);
  62         LTTNG_ASSERT(!ret);
  63         ctf_trace_destroy(trace);
  64 }
  65
  66 /*
  67  * The caller must either:
  68  * - hold the RCU read side lock, or
  69  * - guarantee the existence of the object by already holding a reference to
  70  *   the object.
  71  */
  72 bool ctf_trace_get(struct ctf_trace *trace)
  73 {
  74         const bool ref = urcu_ref_get_unless_zero(&trace->ref);
  75
  76         if (!ref) {
  77                 /*
  78                  * The ref count is already zero. It means the object is being
  79                  * torn down concurently.
  80                  * This is only acceptable if we hold the RCU read-side lock,
  81                  * else it's a logic error.
  82                  */
  83                 ASSERT_RCU_READ_LOCKED();
  84         }
  85
  86         return ref;
  87 }
  88
  89 /*
  90  * Create and return an allocated ctf_trace. NULL on error.
  91  * There is no "open" and "close" for a ctf_trace, but rather just a
  92  * create and refcounting. Whenever all the streams belonging to a trace
  93  * put their reference, its refcount drops to 0.
  94  */
  95 static struct ctf_trace *ctf_trace_create(struct relay_session *session,
  96                 const char *subpath)
  97 {
  98         struct ctf_trace *trace;
  99
 100         trace = zmalloc<ctf_trace>();
 101         if (!trace) {
 102                 PERROR("Failed to allocate ctf_trace");
 103                 goto end;
 104         }
 105         urcu_ref_init(&trace->ref);
 106
 107         if (!session_get(session)) {
 108                 ERR("Failed to acquire session reference");
 109                 goto error;
 110         }
 111         trace->session = session;
 112         trace->path = strdup(subpath);
 113         if (!trace->path) {
 114                 goto error;
 115         }
 116
 117         CDS_INIT_LIST_HEAD(&trace->stream_list);
 118
 119         pthread_mutex_lock(&last_relay_ctf_trace_id_lock);
 120         trace->id = ++last_relay_ctf_trace_id;
 121         pthread_mutex_unlock(&last_relay_ctf_trace_id_lock);
 122
 123         lttng_ht_node_init_str(&trace->node, trace->path);
 124         trace->session = session;
 125         pthread_mutex_init(&trace->lock, NULL);
 126         pthread_mutex_init(&trace->stream_list_lock, NULL);
 127         lttng_ht_add_str(session->ctf_traces_ht, &trace->node);
 128
 129         DBG("Created ctf_trace %" PRIu64 "of session \"%s\" from host \"%s\" with path: %s",
 130                         trace->id, session->session_name, session->hostname,
 131                         subpath);
 132
 133 end:
 134         return trace;
 135 error:
 136         ctf_trace_put(trace);
 137         return NULL;
 138 }
 139
 140 /*
 141  * Return a ctf_trace if found by id in the given hash table else NULL.
 142  * Hold a reference on the ctf_trace, and must be paired with
 143  * ctf_trace_put().
 144  */
 145 struct ctf_trace *ctf_trace_get_by_path_or_create(struct relay_session *session,
 146                 const char *subpath)
 147 {
 148         struct lttng_ht_node_str *node;
 149         struct lttng_ht_iter iter;
 150         struct ctf_trace *trace = NULL;
 151
 152         rcu_read_lock();
 153         lttng_ht_lookup(session->ctf_traces_ht, subpath, &iter);
 154         node = lttng_ht_iter_get_node_str(&iter);
 155         if (!node) {
 156                 DBG("CTF Trace path %s not found", subpath);
 157                 goto end;
 158         }
 159         trace = caa_container_of(node, struct ctf_trace, node);
 160         if (!ctf_trace_get(trace)) {
 161                 trace = NULL;
 162         }
 163 end:
 164         rcu_read_unlock();
 165         if (!trace) {
 166                 /* Try to create */
 167                 trace = ctf_trace_create(session, subpath);
 168         }
 169         return trace;
 170 }
 171
 172 void ctf_trace_put(struct ctf_trace *trace)
 173 {
 174         rcu_read_lock();
 175         urcu_ref_put(&trace->ref, ctf_trace_release);
 176         rcu_read_unlock();
 177 }
 178
 179 int ctf_trace_close(struct ctf_trace *trace)
 180 {
 181         struct relay_stream *stream;
 182
 183         rcu_read_lock();
 184         cds_list_for_each_entry_rcu(stream, &trace->stream_list,
 185                         stream_node) {
 186                 /*
 187                  * Close stream since the connection owning the trace is being
 188                  * torn down.
 189                  */
 190                 try_stream_close(stream);
 191         }
 192         rcu_read_unlock();
 193         /*
 194          * Since all references to the trace are held by its streams, we
 195          * don't need to do any self-ref put.
 196          */
 197         return 0;
 198 }
 199
 200 struct relay_viewer_stream *ctf_trace_get_viewer_metadata_stream(struct ctf_trace *trace)
 201 {
 202         struct relay_viewer_stream *vstream;
 203
 204         rcu_read_lock();
 205         vstream = rcu_dereference(trace->viewer_metadata_stream);
 206         if (!vstream) {
 207                 goto end;
 208         }
 209         if (!viewer_stream_get(vstream)) {
 210                 vstream = NULL;
 211         }
 212 end:
 213         rcu_read_unlock();
 214         return vstream;
 215 }