relay: use urcu_ref_get_unless_zero
[lttng-tools.git] / src / bin / lttng-relayd / viewer-session.c
1 /*
2 * Copyright (C) 2013 - Julien Desfossez <jdesfossez@efficios.com>
3 * David Goulet <dgoulet@efficios.com>
4 * 2015 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License, version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
13 * more details.
14 *
15 * You should have received a copy of the GNU General Public License along with
16 * this program; if not, write to the Free Software Foundation, Inc., 51
17 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18 */
19
20 #define _LGPL_SOURCE
21 #include <common/common.h>
22 #include <urcu/rculist.h>
23
24 #include "lttng-relayd.h"
25 #include "ctf-trace.h"
26 #include "session.h"
27 #include "viewer-session.h"
28 #include "viewer-stream.h"
29 #include "stream.h"
30
31 struct relay_viewer_session *viewer_session_create(void)
32 {
33 struct relay_viewer_session *vsession;
34
35 vsession = zmalloc(sizeof(*vsession));
36 if (!vsession) {
37 goto end;
38 }
39 CDS_INIT_LIST_HEAD(&vsession->session_list);
40 end:
41 return vsession;
42 }
43
44 /* The existence of session must be guaranteed by the caller. */
45 int viewer_session_attach(struct relay_viewer_session *vsession,
46 struct relay_session *session)
47 {
48 int ret = 0;
49
50 /* Will not fail, as per the ownership guarantee. */
51 if (!session_get(session)) {
52 ret = -1;
53 goto end;
54 }
55 pthread_mutex_lock(&session->lock);
56 if (session->viewer_attached) {
57 ret = -1;
58 } else {
59 session->viewer_attached = true;
60 }
61
62 if (!ret) {
63 pthread_mutex_lock(&vsession->session_list_lock);
64 /* Ownership is transfered to the list. */
65 cds_list_add_rcu(&session->viewer_session_node,
66 &vsession->session_list);
67 pthread_mutex_unlock(&vsession->session_list_lock);
68 } else {
69 /* Put our local ref. */
70 session_put(session);
71 }
72 /* Safe since we know the session exists. */
73 pthread_mutex_unlock(&session->lock);
74 end:
75 return ret;
76 }
77
78 /* The existence of session must be guaranteed by the caller. */
79 static int viewer_session_detach(struct relay_viewer_session *vsession,
80 struct relay_session *session)
81 {
82 int ret = 0;
83
84 pthread_mutex_lock(&session->lock);
85 if (!session->viewer_attached) {
86 ret = -1;
87 } else {
88 session->viewer_attached = false;
89 }
90
91 if (!ret) {
92 pthread_mutex_lock(&vsession->session_list_lock);
93 cds_list_del_rcu(&session->viewer_session_node);
94 pthread_mutex_unlock(&vsession->session_list_lock);
95 /* Release reference held by the list. */
96 session_put(session);
97 }
98 /* Safe since we know the session exists. */
99 pthread_mutex_unlock(&session->lock);
100 return ret;
101 }
102
103 void viewer_session_destroy(struct relay_viewer_session *vsession)
104 {
105 free(vsession);
106 }
107
108 /*
109 * Release ownership of all the streams of one session and detach the viewer.
110 */
111 void viewer_session_close_one_session(struct relay_viewer_session *vsession,
112 struct relay_session *session)
113 {
114 struct lttng_ht_iter iter;
115 struct relay_viewer_stream *vstream;
116
117 /*
118 * TODO: improvement: create more efficient list of
119 * vstream per session.
120 */
121 cds_lfht_for_each_entry(viewer_streams_ht->ht, &iter.iter,
122 vstream, stream_n.node) {
123 if (!viewer_stream_get(vstream)) {
124 continue;
125 }
126 if (vstream->stream->trace->session != session) {
127 viewer_stream_put(vstream);
128 continue;
129 }
130 /* Put local reference. */
131 viewer_stream_put(vstream);
132 /*
133 * We have reached one of the viewer stream's lifetime
134 * end condition. This "put" will cause the proper
135 * teardown of the viewer stream.
136 */
137 viewer_stream_put(vstream);
138 }
139
140 viewer_session_detach(vsession, session);
141 }
142
143 void viewer_session_close(struct relay_viewer_session *vsession)
144 {
145 struct relay_session *session;
146
147 rcu_read_lock();
148 cds_list_for_each_entry_rcu(session,
149 &vsession->session_list, viewer_session_node) {
150 viewer_session_close_one_session(vsession, session);
151 }
152 rcu_read_unlock();
153 }
154
155 /*
156 * Check if a connection is attached to a session.
157 * Return 1 if attached, 0 if not attached, a negative value on error.
158 */
159 int viewer_session_is_attached(struct relay_viewer_session *vsession,
160 struct relay_session *session)
161 {
162 struct relay_session *iter;
163 int found = 0;
164
165 pthread_mutex_lock(&session->lock);
166 if (!vsession) {
167 goto end;
168 }
169 if (!session->viewer_attached) {
170 goto end;
171 }
172 rcu_read_lock();
173 cds_list_for_each_entry_rcu(iter,
174 &vsession->session_list,
175 viewer_session_node) {
176 if (session == iter) {
177 found = 1;
178 goto end_rcu_unlock;
179 }
180 }
181 end_rcu_unlock:
182 rcu_read_unlock();
183 end:
184 pthread_mutex_unlock(&session->lock);
185 return found;
186 }
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