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131 .IX Title "threads 3"
132 .TH threads 3 "2009-07-23" "0.9.8k" "OpenSSL"
133 .SH "NAME"
134 CRYPTO_set_locking_callback, CRYPTO_set_id_callback, CRYPTO_num_locks,
135 CRYPTO_set_dynlock_create_callback, CRYPTO_set_dynlock_lock_callback,
136 CRYPTO_set_dynlock_destroy_callback, CRYPTO_get_new_dynlockid,
137 CRYPTO_destroy_dynlockid, CRYPTO_lock \- OpenSSL thread support
138 .SH "SYNOPSIS"
139 .IX Header "SYNOPSIS"
140 .Vb 1
141 \& #include <openssl/crypto.h>
142 .Ve
143 .PP
144 .Vb 2
145 \& void CRYPTO_set_locking_callback(void (*locking_function)(int mode,
146 \& int n, const char *file, int line));
147 .Ve
148 .PP
149 .Vb 1
150 \& void CRYPTO_set_id_callback(unsigned long (*id_function)(void));
151 .Ve
152 .PP
153 .Vb 1
154 \& int CRYPTO_num_locks(void);
155 .Ve
156 .PP
157 .Vb 2
158 \& /* struct CRYPTO_dynlock_value needs to be defined by the user */
159 \& struct CRYPTO_dynlock_value;
160 .Ve
161 .PP
162 .Vb 7
163 \& void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
164 \& (*dyn_create_function)(char *file, int line));
165 \& void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
166 \& (int mode, struct CRYPTO_dynlock_value *l,
167 \& const char *file, int line));
168 \& void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
169 \& (struct CRYPTO_dynlock_value *l, const char *file, int line));
170 .Ve
171 .PP
172 .Vb 1
173 \& int CRYPTO_get_new_dynlockid(void);
174 .Ve
175 .PP
176 .Vb 1
177 \& void CRYPTO_destroy_dynlockid(int i);
178 .Ve
179 .PP
180 .Vb 1
181 \& void CRYPTO_lock(int mode, int n, const char *file, int line);
182 .Ve
183 .PP
184 .Vb 10
185 \& #define CRYPTO_w_lock(type) \e
186 \& CRYPTO_lock(CRYPTO_LOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
187 \& #define CRYPTO_w_unlock(type) \e
188 \& CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
189 \& #define CRYPTO_r_lock(type) \e
190 \& CRYPTO_lock(CRYPTO_LOCK|CRYPTO_READ,type,__FILE__,__LINE__)
191 \& #define CRYPTO_r_unlock(type) \e
192 \& CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_READ,type,__FILE__,__LINE__)
193 \& #define CRYPTO_add(addr,amount,type) \e
194 \& CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)
195 .Ve
196 .SH "DESCRIPTION"
197 .IX Header "DESCRIPTION"
198 OpenSSL can safely be used in multi-threaded applications provided
199 that at least two callback functions are set.
200 .PP
201 locking_function(int mode, int n, const char *file, int line) is
202 needed to perform locking on shared data structures.
203 (Note that OpenSSL uses a number of global data structures that
204 will be implicitly shared whenever multiple threads use OpenSSL.)
205 Multi-threaded applications will crash at random if it is not set.
206 .PP
207 \&\fIlocking_function()\fR must be able to handle up to \fICRYPTO_num_locks()\fR
208 different mutex locks. It sets the \fBn\fR\-th lock if \fBmode\fR &
209 \&\fB\s-1CRYPTO_LOCK\s0\fR, and releases it otherwise.
210 .PP
211 \&\fBfile\fR and \fBline\fR are the file number of the function setting the
212 lock. They can be useful for debugging.
213 .PP
214 id_function(void) is a function that returns a thread \s-1ID\s0, for example
215 \&\fIpthread_self()\fR if it returns an integer (see \s-1NOTES\s0 below). It isn't
216 needed on Windows nor on platforms where \fIgetpid()\fR returns a different
217 \&\s-1ID\s0 for each thread (see \s-1NOTES\s0 below).
218 .PP
219 Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
220 of OpenSSL need it for better performance. To enable this, the following
221 is required:
222 .IP "* Three additional callback function, dyn_create_function, dyn_lock_function and dyn_destroy_function." 4
223 .IX Item "Three additional callback function, dyn_create_function, dyn_lock_function and dyn_destroy_function."
224 .PD 0
225 .IP "* A structure defined with the data that each lock needs to handle." 4
226 .IX Item "A structure defined with the data that each lock needs to handle."
227 .PD
228 .PP
229 struct CRYPTO_dynlock_value has to be defined to contain whatever structure
230 is needed to handle locks.
231 .PP
232 dyn_create_function(const char *file, int line) is needed to create a
233 lock. Multi-threaded applications might crash at random if it is not set.
234 .PP
235 dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int line)
236 is needed to perform locking off dynamic lock numbered n. Multi-threaded
237 applications might crash at random if it is not set.
238 .PP
239 dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is
240 needed to destroy the lock l. Multi-threaded applications might crash at
241 random if it is not set.
242 .PP
243 \&\fICRYPTO_get_new_dynlockid()\fR is used to create locks. It will call
244 dyn_create_function for the actual creation.
245 .PP
246 \&\fICRYPTO_destroy_dynlockid()\fR is used to destroy locks. It will call
247 dyn_destroy_function for the actual destruction.
248 .PP
249 \&\fICRYPTO_lock()\fR is used to lock and unlock the locks. mode is a bitfield
250 describing what should be done with the lock. n is the number of the
251 lock as returned from \fICRYPTO_get_new_dynlockid()\fR. mode can be combined
252 from the following values. These values are pairwise exclusive, with
253 undefined behaviour if misused (for example, \s-1CRYPTO_READ\s0 and \s-1CRYPTO_WRITE\s0
254 should not be used together):
255 .PP
256 .Vb 4
257 \& CRYPTO_LOCK 0x01
258 \& CRYPTO_UNLOCK 0x02
259 \& CRYPTO_READ 0x04
260 \& CRYPTO_WRITE 0x08
261 .Ve
262 .SH "RETURN VALUES"
263 .IX Header "RETURN VALUES"
264 \&\fICRYPTO_num_locks()\fR returns the required number of locks.
265 .PP
266 \&\fICRYPTO_get_new_dynlockid()\fR returns the index to the newly created lock.
267 .PP
268 The other functions return no values.
269 .SH "NOTES"
270 .IX Header "NOTES"
271 You can find out if OpenSSL was configured with thread support:
272 .PP
273 .Vb 7
274 \& #define OPENSSL_THREAD_DEFINES
275 \& #include <openssl/opensslconf.h>
276 \& #if defined(OPENSSL_THREADS)
277 \& // thread support enabled
278 \& #else
279 \& // no thread support
280 \& #endif
281 .Ve
282 .PP
283 Also, dynamic locks are currently not used internally by OpenSSL, but
284 may do so in the future.
285 .PP
286 Defining id_function(void) has it's own issues. Generally speaking,
287 \&\fIpthread_self()\fR should be used, even on platforms where \fIgetpid()\fR gives
288 different answers in each thread, since that may depend on the machine
289 the program is run on, not the machine where the program is being
290 compiled. For instance, Red Hat 8 Linux and earlier used
291 LinuxThreads, whose \fIgetpid()\fR returns a different value for each
292 thread. Red Hat 9 Linux and later use \s-1NPTL\s0, which is
293 Posix\-conformant, and has a \fIgetpid()\fR that returns the same value for
294 all threads in a process. A program compiled on Red Hat 8 and run on
295 Red Hat 9 will therefore see \fIgetpid()\fR returning the same value for
296 all threads.
297 .PP
298 There is still the issue of platforms where \fIpthread_self()\fR returns
299 something other than an integer. This is a bit unusual, and this
300 manual has no cookbook solution for that case.
301 .SH "EXAMPLES"
302 .IX Header "EXAMPLES"
303 \&\fBcrypto/threads/mttest.c\fR shows examples of the callback functions on
304 Solaris, Irix and Win32.
305 .SH "HISTORY"
306 .IX Header "HISTORY"
307 \&\fICRYPTO_set_locking_callback()\fR and \fICRYPTO_set_id_callback()\fR are
308 available in all versions of SSLeay and OpenSSL.
309 \&\fICRYPTO_num_locks()\fR was added in OpenSSL 0.9.4.
310 All functions dealing with dynamic locks were added in OpenSSL 0.9.5b\-dev.
311 .SH "SEE ALSO"
312 .IX Header "SEE ALSO"
313 \&\fIcrypto\fR\|(3)