threads(3SSL)                                OpenSSL                                threads(3SSL)



NAME
       CRYPTO_THREADID_set_callback, CRYPTO_THREADID_get_callback, CRYPTO_THREADID_current,
       CRYPTO_THREADID_cmp, CRYPTO_THREADID_cpy, 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

SYNOPSIS
        #include <openssl/crypto.h>

        /* Don't use this structure directly. */
        typedef struct crypto_threadid_st
                {
                void *ptr;
                unsigned long val;
                } CRYPTO_THREADID;
        /* 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 *);
        void CRYPTO_THREADID_current(CRYPTO_THREADID *id);
        int CRYPTO_THREADID_cmp(const CRYPTO_THREADID *a,
                                const CRYPTO_THREADID *b);
        void CRYPTO_THREADID_cpy(CRYPTO_THREADID *dest,
                                 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)    \
               CRYPTO_lock(CRYPTO_LOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
        #define CRYPTO_w_unlock(type)  \
               CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
        #define CRYPTO_r_lock(type)    \
               CRYPTO_lock(CRYPTO_LOCK|CRYPTO_READ,type,__FILE__,__LINE__)
        #define CRYPTO_r_unlock(type)  \
               CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_READ,type,__FILE__,__LINE__)
        #define CRYPTO_add(addr,amount,type)   \
               CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)

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

       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;

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

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

       ·   CRYPTO_THREADID_cpy() duplicates a thread ID value,

       ·   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:

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

       ·   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 set.

       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

RETURN VALUES
       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.

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

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

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

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

HISTORY
       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'.

SEE ALSO
       crypto(3)



1.0.1t                                      2016-05-03                              threads(3SSL)