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threads(3)			    OpenSSL			    threads(3)

       CRYPTO_THREADID_set_callback, CRYPTO_THREADID_get_callback,
       CRYPTO_THREADID_hash, CRYPTO_set_locking_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>

	/* Don't use this structure directly. */
	typedef	struct crypto_threadid_st
		void *ptr;
		unsigned long val;
	/* Only	use CRYPTO_THREADID_set_[numeric|pointer]() within callbacks */
	void CRYPTO_THREADID_set_numeric(CRYPTO_THREADID *id, unsigned long val);
	void CRYPTO_THREADID_set_pointer(CRYPTO_THREADID *id, void *ptr);
	int CRYPTO_THREADID_set_callback(void (*threadid_func)(CRYPTO_THREADID *));
	void (*CRYPTO_THREADID_get_callback(void))(CRYPTO_THREADID *);
				const CRYPTO_THREADID *b);
				 const CRYPTO_THREADID *src);
	unsigned long CRYPTO_THREADID_hash(const CRYPTO_THREADID *id);

	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 generally be	used safely in multi-threaded applications
       provided	that at	least two callback functions are set, the
       locking_function	and threadid_func.  Note that OpenSSL is not
       completely thread-safe, and unfortunately not all global	resources have
       the necessary locks.  Further, the thread-safety	does not extend	to
       things like multiple threads using the same SSL object at the same

       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.

       threadid_func(CRYPTO_THREADID *id) is needed to record the currently-
       executing thread's identifier into id. The implementation of this
       callback	should not fill	in id directly,	but should use
       CRYPTO_THREADID_set_numeric() if	thread IDs are numeric,	or
       CRYPTO_THREADID_set_pointer() if	they are pointer-based.	 If the
       application does	not register such a callback using
       CRYPTO_THREADID_set_callback(), then a default implementation is	used -
       on Windows and BeOS this	uses the system's default thread identifying
       APIs, and on all	other platforms	it uses	the address of errno. The
       latter is satisfactory for thread-safety	if and only if the platform
       has a thread-local error	number facility.

       Once threadid_func() is registered, or if the built-in default
       implementation is to be used;

       o   CRYPTO_THREADID_current() records the currently-executing thread ID
	   into	the given id object.

       o   CRYPTO_THREADID_cmp() compares two thread IDs (returning zero for
	   equality, ie.  the same semantics as	memcmp()).

       o   CRYPTO_THREADID_cpy() duplicates a thread ID	value,

       o   CRYPTO_THREADID_hash() returns a numeric value usable as a hash-
	   table key. This is usually the exact	numeric	or pointer-based
	   thread ID used internally, however this also	handles	the unusual
	   case	where pointers are larger than 'long' variables	and the
	   platform's thread IDs are pointer-based - in	this case, mixing is
	   done	to attempt to produce a	unique numeric value even though it is
	   not as wide as the platform's true thread IDs.

       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.

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

       CRYPTO_set_locking_callback() is	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.
       CRYPTO_THREADID and associated functions	were introduced	in OpenSSL
       1.0.0 to	replace	(actually, deprecate) the previous
       CRYPTO_set_id_callback(), CRYPTO_get_id_callback(), and
       CRYPTO_thread_id() functions which assumed thread IDs to	always be
       represented by 'unsigned	long'.


1.0.2s				  2019-05-28			    threads(3)


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