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threads(3)			    OpenSSL			    threads(3)

       CRYPTO_set_locking_callback, CRYPTO_set_id_callback, CRYPTO_num_locks,
       CRYPTO_set_dynlock_create_callback, CRYPTO_set_dynlock_lock_callback,
       CRYPTO_set_dynlock_destroy_callback, CRYPTO_get_new_dynlockid,
       CRYPTO_destroy_dynlockid, CRYPTO_lock - OpenSSL thread support

	#include <openssl/crypto.h>

	void CRYPTO_set_locking_callback(void (*locking_function)(int mode,
	       int n, const char *file,	int line));

	void CRYPTO_set_id_callback(unsigned long (*id_function)(void));

	int CRYPTO_num_locks(void);

	/* struct CRYPTO_dynlock_value needs to	be defined by the user */
	struct CRYPTO_dynlock_value;

	void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
	       (*dyn_create_function)(char *file, int line));
	void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
	       (int mode, struct CRYPTO_dynlock_value *l,
	       const char *file, int line));
	void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
	       (struct CRYPTO_dynlock_value *l,	const char *file, int line));

	int CRYPTO_get_new_dynlockid(void);

	void CRYPTO_destroy_dynlockid(int i);

	void CRYPTO_lock(int mode, int n, const	char *file, int	line);

	#define	CRYPTO_w_lock(type)    \
	#define	CRYPTO_w_unlock(type)  \
	#define	CRYPTO_r_lock(type)    \
	#define	CRYPTO_r_unlock(type)  \
	#define	CRYPTO_add(addr,amount,type)   \

       OpenSSL can safely be used in multi-threaded applications provided that
       at least	two callback functions are set.

       locking_function(int mode, int n, const char *file, int line) is	needed
       to perform locking on shared data structures.  (Note that OpenSSL uses
       a number	of global data structures that will be implicitly shared
       whenever	multiple threads use OpenSSL.)	Multi-threaded applications
       will crash at random if it is not set.

       locking_function() must be able to handle up to CRYPTO_num_locks()
       different mutex locks. It sets the n-th lock if mode & CRYPTO_LOCK, and
       releases	it otherwise.

       file and	line are the file number of the	function setting the lock.
       They can	be useful for debugging.

       id_function(void) is a function that returns a thread ID, for example
       pthread_self() if it returns an integer (see NOTES below).  It isn't
       needed on Windows nor on	platforms where	getpid() returns a different
       ID for each thread (see NOTES below).

       Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
       of OpenSSL need it for better performance.  To enable this, the
       following is required:

       o   Three additional callback function, dyn_create_function,
	   dyn_lock_function and dyn_destroy_function.

       o   A structure defined with the	data that each lock needs to handle.

       struct CRYPTO_dynlock_value has to be defined to	contain	whatever
       structure is needed to handle locks.

       dyn_create_function(const char *file, int line) is needed to create a
       lock.  Multi-threaded applications might	crash at random	if it is not

       dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file,	int
       line) is	needed to perform locking off dynamic lock numbered n. Multi-
       threaded	applications might crash at random if it is not	set.

       dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is
       needed to destroy the lock l. Multi-threaded applications might crash
       at random if it is not set.

       CRYPTO_get_new_dynlockid() is used to create locks.  It will call
       dyn_create_function for the actual creation.

       CRYPTO_destroy_dynlockid() is used to destroy locks.  It	will call
       dyn_destroy_function for	the actual destruction.

       CRYPTO_lock() is	used to	lock and unlock	the locks.  mode is a bitfield
       describing what should be done with the lock.  n	is the number of the
       lock as returned	from CRYPTO_get_new_dynlockid().  mode can be combined
       from the	following values.  These values	are pairwise exclusive,	with
       undefined behaviour if misused (for example, CRYPTO_READ	and
       CRYPTO_WRITE should not be used together):

	       CRYPTO_LOCK     0x01
	       CRYPTO_UNLOCK   0x02
	       CRYPTO_READ     0x04
	       CRYPTO_WRITE    0x08

       CRYPTO_num_locks() returns the required number of locks.

       CRYPTO_get_new_dynlockid() returns the index to the newly created lock.

       The other functions return no values.

       You can find out	if OpenSSL was configured with thread support:

	#include <openssl/opensslconf.h>
	#if defined(OPENSSL_THREADS)
	  // thread support enabled
	  // no	thread support

       Also, dynamic locks are currently not used internally by	OpenSSL, but
       may do so in the	future.

       Defining	id_function(void) has it's own issues.	Generally speaking,
       pthread_self() should be	used, even on platforms	where getpid() gives
       different answers in each thread, since that may	depend on the machine
       the program is run on, not the machine where the	program	is being
       compiled.  For instance,	Red Hat	8 Linux	and earlier used LinuxThreads,
       whose getpid() returns a	different value	for each thread.  Red Hat 9
       Linux and later use NPTL, which is Posix-conformant, and	has a getpid()
       that returns the	same value for all threads in a	process.  A program
       compiled	on Red Hat 8 and run on	Red Hat	9 will therefore see getpid()
       returning the same value	for all	threads.

       There is	still the issue	of platforms where pthread_self() returns
       something other than an integer.	 This is a bit unusual,	and this
       manual has no cookbook solution for that	case.

       crypto/threads/mttest.c shows examples of the callback functions	on
       Solaris,	Irix and Win32.

       CRYPTO_set_locking_callback() and CRYPTO_set_id_callback() are
       available in all	versions of SSLeay and OpenSSL.	 CRYPTO_num_locks()
       was added in OpenSSL 0.9.4.  All	functions dealing with dynamic locks
       were added in OpenSSL 0.9.5b-dev.


0.9.8y				  2013-02-05			    threads(3)


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