UNIMPLEMENTED(2) Linux Programmer's Manual UNIMPLEMENTED(2)
NAME
afs_syscall, break, fattach, fdetach, ftime, getmsg, getpmsg, gtty,
isastream, lock, madvise1, mpx, prof, profil, putmsg, putpmsg, secu-
rity, stty, tuxcall, ulimit, vserver - unimplemented system calls
SYNOPSIS
Unimplemented system calls.
DESCRIPTION
These system calls are not implemented in the Linux kernel.
RETURN VALUE
These system calls always return -1 and set errno to ENOSYS.
NOTES
Note that ftime(3), profil(3), and ulimit(3) are implemented as library
functions.
Some system calls, like alloc_hugepages(2), free_hugepages(2), iop-
erm(2), iopl(2), and vm86(2) exist only on certain architectures.
Some system calls, like ipc(2), create_module(2), init_module(2), and
delete_module(2) exist only when the Linux kernel was built with sup-
port for them.
SEE ALSO
syscalls(2)
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 UNIMPLEMENTED(2)
CRYPTO_THREAD_RUN_ONCE(3) OpenSSL CRYPTO_THREAD_RUN_ONCE(3)
NAME
CRYPTO_THREAD_run_once, CRYPTO_THREAD_lock_new,
CRYPTO_THREAD_read_lock, CRYPTO_THREAD_write_lock,
CRYPTO_THREAD_unlock, CRYPTO_THREAD_lock_free, CRYPTO_atomic_add -
OpenSSL thread support
SYNOPSIS
#include <openssl/crypto.h>
CRYPTO_ONCE CRYPTO_ONCE_STATIC_INIT;
int CRYPTO_THREAD_run_once(CRYPTO_ONCE *once, void (*init)(void));
CRYPTO_RWLOCK *CRYPTO_THREAD_lock_new(void);
int CRYPTO_THREAD_read_lock(CRYPTO_RWLOCK *lock);
int CRYPTO_THREAD_write_lock(CRYPTO_RWLOCK *lock);
int CRYPTO_THREAD_unlock(CRYPTO_RWLOCK *lock);
void CRYPTO_THREAD_lock_free(CRYPTO_RWLOCK *lock);
int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock);
DESCRIPTION
OpenSSL can be safely used in multi-threaded applications provided that
support for the underlying OS threading API is built-in. Currently,
OpenSSL supports the pthread and Windows APIs. OpenSSL can also be
built without any multi-threading support, for example on platforms
that don't provide any threading support or that provide a threading
API that is not yet supported by OpenSSL.
The following multi-threading function are provided:
o CRYPTO_THREAD_run_once() can be used to perform one-time
initialization. The once argument must be a pointer to a static
object of type CRYPTO_ONCE that was statically initialized to the
value CRYPTO_ONCE_STATIC_INIT. The init argument is a pointer to a
function that performs the desired exactly once initialization. In
particular, this can be used to allocate locks in a thread-safe
manner, which can then be used with the locking functions below.
o CRYPTO_THREAD_lock_new() allocates, initializes and returns a new
read/write lock.
o CRYPTO_THREAD_read_lock() locks the provided lock for reading.
o CRYPTO_THREAD_write_lock() locks the provided lock for writing.
o CRYPTO_THREAD_unlock() unlocks the previously locked lock.
o CRYPTO_THREAD_lock_free() frees the provided lock.
o CRYPTO_atomic_add() atomically adds amount to val and returns the
result of the operation in ret. lock will be locked, unless atomic
operations are supported on the specific platform. Because of this,
if a variable is modified by CRYPTO_atomic_add() then
CRYPTO_atomic_add() must be the only way that the variable is
modified.
RETURN VALUES
CRYPTO_THREAD_run_once() returns 1 on success, or 0 on error.
CRYPTO_THREAD_lock_new() returns the allocated lock, or NULL on error.
CRYPTO_THREAD_lock_free() returns no value.
The other functions return 1 on success, or 0 on error.
NOTES
On Windows platforms the CRYPTO_THREAD_* types and functions in the
openssl/crypto.h header are dependent on some of the types customarily
made available by including windows.h. The application developer is
likely to require control over when the latter is included, commonly as
one of the first included headers. Therefore, it is defined as an
application developer's responsibility to include windows.h prior to
crypto.h where use of CRYPTO_THREAD_* types and functions is required.
EXAMPLES
This example safely initializes and uses a lock.
#ifdef _WIN32
# include <windows.h>
#endif
#include <openssl/crypto.h>
static CRYPTO_ONCE once = CRYPTO_ONCE_STATIC_INIT;
static CRYPTO_RWLOCK *lock;
static void myinit(void)
{
lock = CRYPTO_THREAD_lock_new();
}
static int mylock(void)
{
if (!CRYPTO_THREAD_run_once(&once, void init) || lock == NULL)
return 0;
return CRYPTO_THREAD_write_lock(lock);
}
static int myunlock(void)
{
return CRYPTO_THREAD_unlock(lock);
}
int serialized(void)
{
int ret = 0;
if (mylock()) {
/* Your code here, do not return without releasing the lock! */
ret = ... ;
}
myunlock();
return ret;
}
Finalization of locks is an advanced topic, not covered in this
example. This can only be done at process exit or when a dynamically
loaded library is no longer in use and is unloaded. The simplest
solution is to just "leak" the lock in applications and not repeatedly
load/unload shared libraries that allocate locks.
NOTES
You can find out if OpenSSL was configured with thread support:
#include <openssl/opensslconf.h>
#if defined(OPENSSL_THREADS)
/* thread support enabled */
#else
/* no thread support */
#endif
SEE ALSO
crypto(7)
COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>;.
1.1.1k 2021-03-25 CRYPTO_THREAD_RUN_ONCE(3)
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