src/bin/lttng-relayd/session.c

   1 /*
   2  * Copyright (C) 2013 - Julien Desfossez <jdesfossez@efficios.com>
   3  *                      David Goulet <dgoulet@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License, version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along with
  15  * this program; if not, write to the Free Software Foundation, Inc., 51
  16  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <common/common.h>
  21
  22 #include "ctf-trace.h"
  23 #include "session.h"
  24 #include "stream.h"
  25
  26 /* Global session id used in the session creation. */
  27 static uint64_t last_relay_session_id;
  28
  29 static void rcu_destroy_session(struct rcu_head *head)
  30 {
  31         struct relay_session *session =
  32                 caa_container_of(head, struct relay_session, rcu_node);
  33
  34         free(session);
  35 }
  36
  37 /*
  38  * Create a new session by assigning a new session ID.
  39  *
  40  * Return allocated session or else NULL.
  41  */
  42 struct relay_session *session_create(void)
  43 {
  44         struct relay_session *session;
  45
  46         session = zmalloc(sizeof(*session));
  47         if (!session) {
  48                 PERROR("relay session zmalloc");
  49                 goto error;
  50         }
  51
  52         session->ctf_traces_ht = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
  53         if (!session->ctf_traces_ht) {
  54                 free(session);
  55                 session = NULL;
  56                 goto error;
  57         }
  58
  59         pthread_mutex_init(&session->viewer_ready_lock, NULL);
  60         session->id = ++last_relay_session_id;
  61         lttng_ht_node_init_u64(&session->session_n, session->id);
  62
  63 error:
  64         return session;
  65 }
  66
  67 /*
  68  * Lookup a session within the given hash table and session id. RCU read side
  69  * lock MUST be acquired before calling this and as long as the caller has a
  70  * reference to the object.
  71  *
  72  * Return session or NULL if not found.
  73  */
  74 struct relay_session *session_find_by_id(struct lttng_ht *ht, uint64_t id)
  75 {
  76         struct relay_session *session = NULL;
  77         struct lttng_ht_node_u64 *node;
  78         struct lttng_ht_iter iter;
  79
  80         assert(ht);
  81
  82         lttng_ht_lookup(ht, &id, &iter);
  83         node = lttng_ht_iter_get_node_u64(&iter);
  84         if (!node) {
  85                 DBG("Session find by ID %" PRIu64 " id NOT found", id);
  86                 goto end;
  87         }
  88         session = caa_container_of(node, struct relay_session, session_n);
  89         DBG("Session find by ID %" PRIu64 " id found", id);
  90
  91 end:
  92         return session;
  93 }
  94
  95 /*
  96  * Delete session from the given hash table.
  97  *
  98  * Return lttng ht del error code being 0 on success and 1 on failure.
  99  */
 100 int session_delete(struct lttng_ht *ht, struct relay_session *session)
 101 {
 102         struct lttng_ht_iter iter;
 103
 104         assert(ht);
 105         assert(session);
 106
 107         iter.iter.node = &session->session_n.node;
 108         return lttng_ht_del(ht, &iter);
 109 }
 110
 111 /*
 112  * The caller MUST be from the viewer thread since the viewer refcount is
 113  * decremented. With this calue down to 0, it will try to destroy the session.
 114  */
 115 void session_viewer_try_destroy(struct lttng_ht *ht,
 116                 struct relay_session *session)
 117 {
 118         unsigned long ret_ref;
 119
 120         assert(session);
 121
 122         ret_ref = uatomic_add_return(&session->viewer_refcount, -1);
 123         if (ret_ref == 0) {
 124                 session_try_destroy(ht, session);
 125         }
 126 }
 127
 128 /*
 129  * Should only be called from the main streaming thread since it does not touch
 130  * the viewer refcount. If this refcount is down to 0, destroy the session only
 131  * and only if the session deletion succeeds. This is done because the viewer
 132  * *and* the streaming thread can both concurently try to destroy the session
 133  * thus the first come first serve.
 134  */
 135 void session_try_destroy(struct lttng_ht *ht, struct relay_session *session)
 136 {
 137         int ret = 0;
 138         unsigned long ret_ref;
 139
 140         assert(session);
 141
 142         ret_ref = uatomic_read(&session->viewer_refcount);
 143         if (ret_ref == 0 && session->close_flag) {
 144                 if (ht) {
 145                         ret = session_delete(ht, session);
 146                 }
 147                 if (!ret) {
 148                         /* Only destroy the session if the deletion was successful. */
 149                         session_destroy(session);
 150                 }
 151         }
 152 }
 153
 154 /*
 155  * Destroy a session object.
 156  *
 157  * This function must *NOT* be called with an RCU read lock held since
 158  * the session's ctf_traces_ht is destroyed.
 159  */
 160 void session_destroy(struct relay_session *session)
 161 {
 162         struct ctf_trace *ctf_trace;
 163         struct lttng_ht_iter iter;
 164
 165         assert(session);
 166
 167         DBG("Relay destroying session %" PRIu64, session->id);
 168
 169         /*
 170          * Empty the ctf trace hash table which will destroy the stream contained
 171          * in that table.
 172          */
 173         rcu_read_lock();
 174         cds_lfht_for_each_entry(session->ctf_traces_ht->ht, &iter.iter, ctf_trace,
 175                         node.node) {
 176                 ctf_trace_delete(session->ctf_traces_ht, ctf_trace);
 177                 ctf_trace_destroy(ctf_trace);
 178         }
 179         rcu_read_unlock();
 180         lttng_ht_destroy(session->ctf_traces_ht);
 181
 182         call_rcu(&session->rcu_node, rcu_destroy_session);
 183 }