Jack2  1.9.12
JackLinuxFutex.cpp
1 /*
2 Copyright (C) 2004-2008 Grame
3 Copyright (C) 2016 Filipe Coelho
4 
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as published by
7 the Free Software Foundation; either version 2.1 of the License, or
8 (at your option) any later version.
9 
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
14 
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program; if not, write to the Free Software
17 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 
19 */
20 
21 #include "JackLinuxFutex.h"
22 #include "JackTools.h"
23 #include "JackConstants.h"
24 #include "JackError.h"
25 #include "promiscuous.h"
26 #include <fcntl.h>
27 #include <stdio.h>
28 #include <sys/mman.h>
29 #include <syscall.h>
30 #include <linux/futex.h>
31 
32 namespace Jack
33 {
34 
35 JackLinuxFutex::JackLinuxFutex() : JackSynchro(), fSharedMem(-1), fFutex(NULL), fPrivate(false)
36 {
37  const char* promiscuous = getenv("JACK_PROMISCUOUS_SERVER");
38  fPromiscuous = (promiscuous != NULL);
39  fPromiscuousGid = jack_group2gid(promiscuous);
40 }
41 
42 void JackLinuxFutex::BuildName(const char* client_name, const char* server_name, char* res, int size)
43 {
44  char ext_client_name[SYNC_MAX_NAME_SIZE + 1];
45  JackTools::RewriteName(client_name, ext_client_name);
46  if (fPromiscuous) {
47  snprintf(res, size, "jack_sem.%s_%s", server_name, ext_client_name);
48  } else {
49  snprintf(res, size, "jack_sem.%d_%s_%s", JackTools::GetUID(), server_name, ext_client_name);
50  }
51 }
52 
53 bool JackLinuxFutex::Signal()
54 {
55  if (!fFutex) {
56  jack_error("JackLinuxFutex::Signal name = %s already deallocated!!", fName);
57  return false;
58  }
59 
60  if (fFlush) {
61  return true;
62  }
63 
64  if (! __sync_bool_compare_and_swap(&fFutex->futex, 0, 1))
65  {
66  // already unlocked, do not wake futex
67  if (! fFutex->internal) return true;
68  }
69 
70  ::syscall(__NR_futex, fFutex, fFutex->internal ? FUTEX_WAKE_PRIVATE : FUTEX_WAKE, 1, NULL, NULL, 0);
71  return true;
72 }
73 
74 bool JackLinuxFutex::SignalAll()
75 {
76  return Signal();
77 }
78 
79 bool JackLinuxFutex::Wait()
80 {
81  if (!fFutex) {
82  jack_error("JackLinuxFutex::Wait name = %s already deallocated!!", fName);
83  return false;
84  }
85 
86  if (fFutex->needsChange)
87  {
88  fFutex->needsChange = false;
89  fFutex->internal = !fFutex->internal;
90  }
91 
92  for (;;)
93  {
94  if (__sync_bool_compare_and_swap(&fFutex->futex, 1, 0))
95  return true;
96 
97  if (::syscall(__NR_futex, fFutex, fFutex->internal ? FUTEX_WAIT_PRIVATE : FUTEX_WAIT, 0, NULL, NULL, 0) != 0 && errno != EWOULDBLOCK)
98  return false;
99  }
100 }
101 
102 bool JackLinuxFutex::TimedWait(long usec)
103 {
104  if (!fFutex) {
105  jack_error("JackLinuxFutex::TimedWait name = %s already deallocated!!", fName);
106  return false;
107  }
108 
109  if (fFutex->needsChange)
110  {
111  fFutex->needsChange = false;
112  fFutex->internal = !fFutex->internal;
113  }
114 
115  const uint secs = usec / 1000000;
116  const int nsecs = (usec % 1000000) * 1000;
117 
118  const timespec timeout = { static_cast<time_t>(secs), nsecs };
119 
120  for (;;)
121  {
122  if (__sync_bool_compare_and_swap(&fFutex->futex, 1, 0))
123  return true;
124 
125  if (::syscall(__NR_futex, fFutex, fFutex->internal ? FUTEX_WAIT_PRIVATE : FUTEX_WAIT, 0, &timeout, NULL, 0) != 0 && errno != EWOULDBLOCK)
126  return false;
127  }
128 }
129 
130 // Server side : publish the futex in the global namespace
131 bool JackLinuxFutex::Allocate(const char* name, const char* server_name, int value, bool internal)
132 {
133  BuildName(name, server_name, fName, sizeof(fName));
134  jack_log("JackLinuxFutex::Allocate name = %s val = %ld", fName, value);
135 
136  if ((fSharedMem = shm_open(fName, O_CREAT | O_RDWR, 0777)) < 0) {
137  jack_error("Allocate: can't check in named futex name = %s err = %s", fName, strerror(errno));
138  return false;
139  }
140 
141  ftruncate(fSharedMem, sizeof(FutexData));
142 
143  if (fPromiscuous && (jack_promiscuous_perms(fSharedMem, fName, fPromiscuousGid) < 0)) {
144  close(fSharedMem);
145  fSharedMem = -1;
146  shm_unlink(fName);
147  return false;
148  }
149 
150  if ((fFutex = (FutexData*)mmap(NULL, sizeof(FutexData), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED, fSharedMem, 0)) == NULL) {
151  jack_error("Allocate: can't check in named futex name = %s err = %s", fName, strerror(errno));
152  close(fSharedMem);
153  fSharedMem = -1;
154  shm_unlink(fName);
155  return false;
156  }
157 
158  fPrivate = internal;
159 
160  fFutex->futex = value;
161  fFutex->internal = internal;
162  fFutex->wasInternal = internal;
163  fFutex->needsChange = false;
164  fFutex->externalCount = 0;
165  return true;
166 }
167 
168 // Client side : get the published futex from server
169 bool JackLinuxFutex::Connect(const char* name, const char* server_name)
170 {
171  BuildName(name, server_name, fName, sizeof(fName));
172  jack_log("JackLinuxFutex::Connect name = %s", fName);
173 
174  // Temporary...
175  if (fFutex) {
176  jack_log("Already connected name = %s", name);
177  return true;
178  }
179 
180  if ((fSharedMem = shm_open(fName, O_RDWR, 0)) < 0) {
181  jack_error("Connect: can't connect named futex name = %s err = %s", fName, strerror(errno));
182  return false;
183  }
184 
185  if ((fFutex = (FutexData*)mmap(NULL, sizeof(FutexData), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED, fSharedMem, 0)) == NULL) {
186  jack_error("Connect: can't connect named futex name = %s err = %s", fName, strerror(errno));
187  close(fSharedMem);
188  fSharedMem = -1;
189  return false;
190  }
191 
192  if (! fPrivate && fFutex->wasInternal)
193  {
194  const char* externalSync = getenv("JACK_INTERNAL_CLIENT_SYNC");
195 
196  if (externalSync != NULL && strstr(fName, externalSync) != NULL && ++fFutex->externalCount == 1)
197  {
198  jack_error("Note: client %s running as external client temporarily", fName);
199  fFutex->needsChange = true;
200  }
201  }
202 
203  return true;
204 }
205 
206 bool JackLinuxFutex::ConnectInput(const char* name, const char* server_name)
207 {
208  return Connect(name, server_name);
209 }
210 
211 bool JackLinuxFutex::ConnectOutput(const char* name, const char* server_name)
212 {
213  return Connect(name, server_name);
214 }
215 
216 bool JackLinuxFutex::Disconnect()
217 {
218  if (!fFutex) {
219  return true;
220  }
221 
222  if (! fPrivate && fFutex->wasInternal)
223  {
224  const char* externalSync = getenv("JACK_INTERNAL_CLIENT_SYNC");
225 
226  if (externalSync != NULL && strstr(fName, externalSync) != NULL && --fFutex->externalCount == 0)
227  {
228  jack_error("Note: client %s now running as internal client again", fName);
229  fFutex->needsChange = true;
230  }
231  }
232 
233  munmap(fFutex, sizeof(FutexData));
234  fFutex = NULL;
235 
236  close(fSharedMem);
237  fSharedMem = -1;
238  return true;
239 }
240 
241 // Server side : destroy the futex
242 void JackLinuxFutex::Destroy()
243 {
244  if (!fFutex) {
245  return;
246  }
247 
248  munmap(fFutex, sizeof(FutexData));
249  fFutex = NULL;
250 
251  close(fSharedMem);
252  fSharedMem = -1;
253 
254  shm_unlink(fName);
255 }
256 
257 } // end of namespace
258 
jack_log
SERVER_EXPORT void jack_log(const char *fmt,...)
Definition: JackError.cpp:108
jack_error
SERVER_EXPORT void jack_error(const char *fmt,...)
Definition: JackError.cpp:92