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  FutexData* futex = (FutexData*)mmap(NULL, sizeof(FutexData), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED, fSharedMem, 0);
151 
152  if (futex == NULL || futex == MAP_FAILED) {
153  jack_error("Allocate: can't check in named futex name = %s err = %s", fName, strerror(errno));
154  close(fSharedMem);
155  fSharedMem = -1;
156  shm_unlink(fName);
157  return false;
158  }
159 
160  fPrivate = internal;
161 
162  futex->futex = value;
163  futex->internal = internal;
164  futex->wasInternal = internal;
165  futex->needsChange = false;
166  futex->externalCount = 0;
167  fFutex = futex;
168  return true;
169 }
170 
171 // Client side : get the published futex from server
172 bool JackLinuxFutex::Connect(const char* name, const char* server_name)
173 {
174  BuildName(name, server_name, fName, sizeof(fName));
175  jack_log("JackLinuxFutex::Connect name = %s", fName);
176 
177  // Temporary...
178  if (fFutex) {
179  jack_log("Already connected name = %s", name);
180  return true;
181  }
182 
183  if ((fSharedMem = shm_open(fName, O_RDWR, 0)) < 0) {
184  jack_error("Connect: can't connect named futex name = %s err = %s", fName, strerror(errno));
185  return false;
186  }
187 
188  FutexData* futex = (FutexData*)mmap(NULL, sizeof(FutexData), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_LOCKED, fSharedMem, 0);
189 
190  if (futex == NULL || futex == MAP_FAILED) {
191  jack_error("Connect: can't connect named futex name = %s err = %s", fName, strerror(errno));
192  close(fSharedMem);
193  fSharedMem = -1;
194  return false;
195  }
196 
197  if (! fPrivate && futex->wasInternal)
198  {
199  const char* externalSync = getenv("JACK_INTERNAL_CLIENT_SYNC");
200 
201  if (externalSync != NULL && strstr(fName, externalSync) != NULL && ++futex->externalCount == 1)
202  {
203  jack_error("Note: client %s running as external client temporarily", fName);
204  futex->needsChange = true;
205  }
206  }
207 
208  fFutex = futex;
209  return true;
210 }
211 
212 bool JackLinuxFutex::ConnectInput(const char* name, const char* server_name)
213 {
214  return Connect(name, server_name);
215 }
216 
217 bool JackLinuxFutex::ConnectOutput(const char* name, const char* server_name)
218 {
219  return Connect(name, server_name);
220 }
221 
222 bool JackLinuxFutex::Disconnect()
223 {
224  if (!fFutex) {
225  return true;
226  }
227 
228  if (! fPrivate && fFutex->wasInternal)
229  {
230  const char* externalSync = getenv("JACK_INTERNAL_CLIENT_SYNC");
231 
232  if (externalSync != NULL && strstr(fName, externalSync) != NULL && --fFutex->externalCount == 0)
233  {
234  jack_error("Note: client %s now running as internal client again", fName);
235  fFutex->needsChange = true;
236  }
237  }
238 
239  munmap(fFutex, sizeof(FutexData));
240  fFutex = NULL;
241 
242  close(fSharedMem);
243  fSharedMem = -1;
244  return true;
245 }
246 
247 // Server side : destroy the futex
248 void JackLinuxFutex::Destroy()
249 {
250  if (!fFutex) {
251  return;
252  }
253 
254  munmap(fFutex, sizeof(FutexData));
255  fFutex = NULL;
256 
257  close(fSharedMem);
258  fSharedMem = -1;
259 
260  shm_unlink(fName);
261 }
262 
263 } // end of namespace
264 
SERVER_EXPORT void jack_error(const char *fmt,...)
Definition: JackError.cpp:92
SERVER_EXPORT void jack_log(const char *fmt,...)
Definition: JackError.cpp:108