5 CRYPTO_THREAD_run_once,
6 CRYPTO_THREAD_lock_new, CRYPTO_THREAD_read_lock, CRYPTO_THREAD_write_lock,
7 CRYPTO_THREAD_unlock, CRYPTO_THREAD_lock_free,
8 CRYPTO_atomic_add, CRYPTO_atomic_or, CRYPTO_atomic_load,
9 CRYPTO_atomic_load_int,
10 OSSL_set_max_threads, OSSL_get_max_threads,
11 OSSL_get_thread_support_flags, OSSL_THREAD_SUPPORT_FLAG_THREAD_POOL,
12 OSSL_THREAD_SUPPORT_FLAG_DEFAULT_SPAWN - OpenSSL thread support
16 #include <openssl/crypto.h>
18 CRYPTO_ONCE CRYPTO_ONCE_STATIC_INIT;
19 int CRYPTO_THREAD_run_once(CRYPTO_ONCE *once, void (*init)(void));
21 CRYPTO_RWLOCK *CRYPTO_THREAD_lock_new(void);
22 int CRYPTO_THREAD_read_lock(CRYPTO_RWLOCK *lock);
23 int CRYPTO_THREAD_write_lock(CRYPTO_RWLOCK *lock);
24 int CRYPTO_THREAD_unlock(CRYPTO_RWLOCK *lock);
25 void CRYPTO_THREAD_lock_free(CRYPTO_RWLOCK *lock);
27 int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock);
28 int CRYPTO_atomic_or(uint64_t *val, uint64_t op, uint64_t *ret,
30 int CRYPTO_atomic_load(uint64_t *val, uint64_t *ret, CRYPTO_RWLOCK *lock);
31 int CRYPTO_atomic_load_int(int *val, int *ret, CRYPTO_RWLOCK *lock);
33 int OSSL_set_max_threads(OSSL_LIB_CTX *ctx, uint64_t max_threads);
34 uint64_t OSSL_get_max_threads(OSSL_LIB_CTX *ctx);
35 uint32_t OSSL_get_thread_support_flags(void);
37 #define OSSL_THREAD_SUPPORT_FLAG_THREAD_POOL
38 #define OSSL_THREAD_SUPPORT_FLAG_DEFAULT_SPAWN
42 OpenSSL can be safely used in multi-threaded applications provided that
43 support for the underlying OS threading API is built-in. Currently, OpenSSL
44 supports the pthread and Windows APIs. OpenSSL can also be built without
45 any multi-threading support, for example on platforms that don't provide
46 any threading support or that provide a threading API that is not yet
49 The following multi-threading function are provided:
55 CRYPTO_THREAD_run_once() can be used to perform one-time initialization.
56 The I<once> argument must be a pointer to a static object of type
57 B<CRYPTO_ONCE> that was statically initialized to the value
58 B<CRYPTO_ONCE_STATIC_INIT>.
59 The I<init> argument is a pointer to a function that performs the desired
60 exactly once initialization.
61 In particular, this can be used to allocate locks in a thread-safe manner,
62 which can then be used with the locking functions below.
66 CRYPTO_THREAD_lock_new() allocates, initializes and returns a new read/write
71 CRYPTO_THREAD_read_lock() locks the provided I<lock> for reading.
75 CRYPTO_THREAD_write_lock() locks the provided I<lock> for writing.
79 CRYPTO_THREAD_unlock() unlocks the previously locked I<lock>.
83 CRYPTO_THREAD_lock_free() frees the provided I<lock>.
87 CRYPTO_atomic_add() atomically adds I<amount> to I<*val> and returns the
88 result of the operation in I<*ret>. I<lock> will be locked, unless atomic
89 operations are supported on the specific platform. Because of this, if a
90 variable is modified by CRYPTO_atomic_add() then CRYPTO_atomic_add() must
91 be the only way that the variable is modified. If atomic operations are not
92 supported and I<lock> is NULL, then the function will fail.
96 CRYPTO_atomic_or() performs an atomic bitwise or of I<op> and I<*val> and stores
97 the result back in I<*val>. It also returns the result of the operation in
98 I<*ret>. I<lock> will be locked, unless atomic operations are supported on the
99 specific platform. Because of this, if a variable is modified by
100 CRYPTO_atomic_or() or read by CRYPTO_atomic_load() then CRYPTO_atomic_or() must
101 be the only way that the variable is modified. If atomic operations are not
102 supported and I<lock> is NULL, then the function will fail.
106 CRYPTO_atomic_load() atomically loads the contents of I<*val> into I<*ret>.
107 I<lock> will be locked, unless atomic operations are supported on the specific
108 platform. Because of this, if a variable is modified by CRYPTO_atomic_or() or
109 read by CRYPTO_atomic_load() then CRYPTO_atomic_load() must be the only way that
110 the variable is read. If atomic operations are not supported and I<lock> is
111 NULL, then the function will fail.
115 CRYPTO_atomic_load_int() works identically to CRYPTO_atomic_load() but operates
116 on an I<int> value instead of a I<uint64_t> value.
120 OSSL_set_max_threads() sets the maximum number of threads to be used by the
121 thread pool. If the argument is 0, thread pooling is disabled. OpenSSL will
122 not create any threads and existing threads in the thread pool will be torn
123 down. The maximum thread count is a limit, not a target. Threads will not be
124 spawned unless (and until) there is demand. Thread polling is disabled by
125 default. To enable threading you must call OSSL_set_max_threads() explicitly.
126 Under no circumstances is this done for you.
130 OSSL_get_thread_support_flags() determines what thread pool functionality
131 OpenSSL is compiled with and is able to support in the current run time
132 environment. B<OSSL_THREAD_SUPPORT_FLAG_THREAD_POOL> indicates that the base
133 thread pool functionality is available, and
134 B<OSSL_THREAD_SUPPORT_FLAG_DEFAULT_SPAWN> indicates that the default thread pool
135 model is available. The default thread pool model is currently the only model
136 available, therefore both of these flags must be set for thread pool
137 functionality to be used.
143 CRYPTO_THREAD_run_once() returns 1 on success, or 0 on error.
145 CRYPTO_THREAD_lock_new() returns the allocated lock, or NULL on error.
147 CRYPTO_THREAD_lock_free() returns no value.
149 OSSL_set_max_threads() returns 1 on success and 0 on failure. Returns failure
150 if OpenSSL-managed thread pooling is not supported (for example, if it is not
151 supported on the current platform, or because OpenSSL is not built with the
154 OSSL_get_max_threads() returns the maximum number of threads currently allowed
155 to be used by the thread pool. If thread pooling is disabled or not available,
158 OSSL_get_thread_support_flags() returns zero or more B<OSSL_THREAD_SUPPORT_FLAG>
161 The other functions return 1 on success, or 0 on error.
165 On Windows platforms the CRYPTO_THREAD_* types and functions in the
166 F<< <openssl/crypto.h> >> header are dependent on some of the types
167 customarily made available by including F<< <windows.h> >>. The application
168 developer is likely to require control over when the latter is included,
169 commonly as one of the first included headers. Therefore, it is defined as an
170 application developer's responsibility to include F<< <windows.h> >> prior to
171 F<< <openssl/crypto.h> >> where use of CRYPTO_THREAD_* types and functions is
176 You can find out if OpenSSL was configured with thread support:
178 #include <openssl/opensslconf.h>
179 #if defined(OPENSSL_THREADS)
180 /* thread support enabled */
182 /* no thread support */
185 This example safely initializes and uses a lock.
188 # include <windows.h>
190 #include <openssl/crypto.h>
192 static CRYPTO_ONCE once = CRYPTO_ONCE_STATIC_INIT;
193 static CRYPTO_RWLOCK *lock;
195 static void myinit(void)
197 lock = CRYPTO_THREAD_lock_new();
200 static int mylock(void)
202 if (!CRYPTO_THREAD_run_once(&once, void init) || lock == NULL)
204 return CRYPTO_THREAD_write_lock(lock);
207 static int myunlock(void)
209 return CRYPTO_THREAD_unlock(lock);
217 /* Your code here, do not return without releasing the lock! */
224 Finalization of locks is an advanced topic, not covered in this example.
225 This can only be done at process exit or when a dynamically loaded library is
226 no longer in use and is unloaded.
227 The simplest solution is to just "leak" the lock in applications and not
228 repeatedly load/unload shared libraries that allocate locks.
232 L<crypto(7)>, L<openssl-threads(7)>.
236 Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
238 Licensed under the Apache License 2.0 (the "License"). You may not use
239 this file except in compliance with the License. You can obtain a copy
240 in the file LICENSE in the source distribution or at
241 L<https://www.openssl.org/source/license.html>.