iv_tls(3)						    ivykis programmer's manual							 iv_tls(3)

NAME

       iv_tls_user_register, iv_tls_user_ptr - thread-local storage handling for ivykis modules

SYNOPSIS

       #include <iv_tls.h>

       struct iv_tls_user {
	       size_t	       sizeof_state;
	       void	       (*init_thread)(void *st);
	       void	       (*deinit_thread)(void *st);
       };

       void iv_tls_user_register(struct iv_tls_user *tu);
       void *iv_tls_user_ptr(struct iv_tls_user *tu);

DESCRIPTION

       The iv_tls interface provides thread-local storage handling to ivykis modules.

       An  ivykis  module  can	arrange for an amount of memory to be allocated for its use in each ivykis thread by calling iv_tls_user_register.
       This must be done before any calls to iv_init have been made in this process, and is typically done from a module  initialization  function
       marked as a constructor function.

       The  ->sizeof_state  member  of	the passed-in structure indicates how many bytes of memory the module wants allocated for its use in every
       ivykis thread.

       When a thread calls iv_init, ->sizeof_state bytes of memory will be allocated for use by this module in that  thread,  and  initialised	to
       zero.  A pointer to this memory area can be obtained by calling iv_tls_user_ptr (which returns NULL in non-ivykis threads).

       If  the	specified ->init_thread function pointer is not NULL, it will be invoked at the end of iv_init, with its argument pointing to this
       thread's memory area allocation for this module.

       If ->deinit_thread is not NULL, it will be invoked at the start of iv_deinit, or if the thread fails to call iv_deinit before  terminating,
       at thread termination time.  The argument passed into ->deinit_thread is the same as for ->init_thread.

       It is permitted to call any ivykis API functions from the ->init_thread and ->deinit_thread callbacks.

       There is no explicit serialization on calls to ->init_thread and ->deinit_thread.

       Care  must  be  taken  when  calling iv_tls_user_ptr from a signal handler, as there is a time window where it will return a non-NULL value
       before ->init_thread or after ->deinit_thread have been called.

       Use of iv_tls for managing thread-local state is preferred over direct use of the __thread keyword, as not all platforms that  ivykis  runs
       on provide the __thread keyword.

       Use  of	iv_tls	for  managing  thread-local  state is preferred over direct use of the pthread_key_create and pthread_setspecific APIs, as
       iv_tls provides a thread init hook as well as a destructor hook, and properly sequences ->init_thread and ->deinit_thread calls	with  core
       ivykis initialization and cleanup.

SEE ALSO

       iv_init(3)

ivykis								    2012-03-30								 iv_tls(3)