Manual Pages for UNIX Operating System command usage for man CRYPTO_num_locks

OpenSSL                                         threads(3openssl)



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     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

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      #include 

      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)    \
             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__)


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





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OpenSSL                                         threads(3openssl)



     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 nnnn-th
     lock if mmmmooooddddeeee & CCCCRRRRYYYYPPPPTTTTOOOO_LLLLOOOOCCCCKKKK, and releases it otherwise.

     ffffiiiilllleeee and lllliiiinnnneeee 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:

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

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

     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.




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OpenSSL                                         threads(3openssl)



     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


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     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.

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

      #define OPENSSL_THREAD_DEFINES
      #include 
      #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.

     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



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OpenSSL                                         threads(3openssl)



     unusual, and this manual has no cookbook solution for that
     case.

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     ccccrrrryyyyppppttttoooo////tttthhhhrrrreeeeaaaaddddssss////mmmmtttttttteeeesssstttt....cccc shows examples of the callback
     functions on Solaris, Irix and Win32.

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     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.

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     crypto(3)







































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