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 "ctf-trace.hpp"
  13 #include "lttng-relayd.hpp"
  14 #include "stream.hpp"
  15
  16 #include <common/common.hpp>
  17 #include <common/urcu.hpp>
  18 #include <common/utils.hpp>
  19
  20 #include <urcu/rculist.h>
  21
  22 static uint64_t last_relay_ctf_trace_id;
  23 static pthread_mutex_t last_relay_ctf_trace_id_lock = PTHREAD_MUTEX_INITIALIZER;
  24
  25 static void rcu_destroy_ctf_trace(struct rcu_head *rcu_head)
  26 {
  27         struct ctf_trace *trace = lttng::utils::container_of(rcu_head, &ctf_trace::rcu_node);
  28
  29         free(trace);
  30 }
  31
  32 /*
  33  * Destroy a ctf trace and all stream contained in it.
  34  *
  35  * MUST be called with the RCU read side lock.
  36  */
  37 static void ctf_trace_destroy(struct ctf_trace *trace)
  38 {
  39         /*
  40          * Getting to this point, every stream referenced by that trace
  41          * have put back their ref since the've been closed by the
  42          * control side.
  43          */
  44         LTTNG_ASSERT(cds_list_empty(&trace->stream_list));
  45         ASSERT_RCU_READ_LOCKED();
  46
  47         session_put(trace->session);
  48         trace->session = nullptr;
  49         free(trace->path);
  50         trace->path = nullptr;
  51         call_rcu(&trace->rcu_node, rcu_destroy_ctf_trace);
  52 }
  53
  54 static void ctf_trace_release(struct urcu_ref *ref)
  55 {
  56         struct ctf_trace *trace = lttng::utils::container_of(ref, &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, const char *subpath)
  96 {
  97         struct ctf_trace *trace;
  98
  99         trace = zmalloc<ctf_trace>();
 100         if (!trace) {
 101                 PERROR("Failed to allocate ctf_trace");
 102                 goto end;
 103         }
 104         urcu_ref_init(&trace->ref);
 105
 106         if (!session_get(session)) {
 107                 ERR("Failed to acquire session reference");
 108                 goto error;
 109         }
 110         trace->session = session;
 111         trace->path = strdup(subpath);
 112         if (!trace->path) {
 113                 goto error;
 114         }
 115
 116         CDS_INIT_LIST_HEAD(&trace->stream_list);
 117
 118         pthread_mutex_lock(&last_relay_ctf_trace_id_lock);
 119         trace->id = ++last_relay_ctf_trace_id;
 120         pthread_mutex_unlock(&last_relay_ctf_trace_id_lock);
 121
 122         lttng_ht_node_init_str(&trace->node, trace->path);
 123         trace->session = session;
 124         pthread_mutex_init(&trace->lock, nullptr);
 125         pthread_mutex_init(&trace->stream_list_lock, nullptr);
 126         lttng_ht_add_str(session->ctf_traces_ht, &trace->node);
 127
 128         DBG("Created ctf_trace %" PRIu64 " of session \"%s\" from host \"%s\" with path: %s",
 129             trace->id,
 130             session->session_name,
 131             session->hostname,
 132             subpath);
 133
 134 end:
 135         return trace;
 136 error:
 137         ctf_trace_put(trace);
 138         return nullptr;
 139 }
 140
 141 /*
 142  * Return a ctf_trace if found by id in the given hash table else NULL.
 143  * Hold a reference on the ctf_trace, and must be paired with
 144  * ctf_trace_put().
 145  */
 146 struct ctf_trace *ctf_trace_get_by_path_or_create(struct relay_session *session,
 147                                                   const char *subpath)
 148 {
 149         struct lttng_ht_node_str *node;
 150         struct lttng_ht_iter iter;
 151         struct ctf_trace *trace = nullptr;
 152
 153         lttng::urcu::read_lock_guard read_lock;
 154         lttng_ht_lookup(session->ctf_traces_ht, subpath, &iter);
 155         node = lttng_ht_iter_get_node_str(&iter);
 156         if (!node) {
 157                 DBG("CTF Trace path %s not found", subpath);
 158                 goto end;
 159         }
 160         trace = lttng::utils::container_of(node, &ctf_trace::node);
 161         if (!ctf_trace_get(trace)) {
 162                 trace = nullptr;
 163         }
 164 end:
 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         lttng::urcu::read_lock_guard read_lock;
 175         urcu_ref_put(&trace->ref, ctf_trace_release);
 176 }
 177
 178 int ctf_trace_close(struct ctf_trace *trace)
 179 {
 180         struct relay_stream *stream;
 181
 182         lttng::urcu::read_lock_guard read_lock;
 183         cds_list_for_each_entry_rcu(stream, &trace->stream_list, stream_node)
 184         {
 185                 /*
 186                  * Close stream since the connection owning the trace is being
 187                  * torn down.
 188                  */
 189                 try_stream_close(stream);
 190         }
 191         /*
 192          * Since all references to the trace are held by its streams, we
 193          * don't need to do any self-ref put.
 194          */
 195         return 0;
 196 }
 197
 198 struct relay_viewer_stream *ctf_trace_get_viewer_metadata_stream(struct ctf_trace *trace)
 199 {
 200         struct relay_viewer_stream *vstream;
 201
 202         lttng::urcu::read_lock_guard read_lock;
 203         vstream = rcu_dereference(trace->viewer_metadata_stream);
 204         if (!vstream) {
 205                 goto end;
 206         }
 207         if (!viewer_stream_get(vstream)) {
 208                 vstream = nullptr;
 209         }
 210 end:
 211         return vstream;
 212 }