DragonFly On-Line Manual Pages

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

NAME
       IV_WAIT_INTEREST_INIT, iv_wait_interest_register,
       iv_wait_interest_register_spawn, iv_wait_interest_unregister,
       iv_wait_interest_kill - ivykis wait4(2) wrapper

SYNOPSIS
       #include <iv_wait.h>

       struct iv_wait_interest {
               pid_t           pid;
               void            *cookie;
               void            (*handler)(void *cookie, int status,
                                          const struct rusage *rusage);
       };

       void IV_WAIT_INTEREST_INIT(struct iv_wait_interest *this);
       int iv_wait_interest_register(struct iv_wait_interest *this);
       int iv_wait_interest_register_spawn(struct iv_wait_interest *this, void
       (*fn)(void *), void *cookie);
       void iv_wait_interest_unregister(struct iv_wait_interest *this);
       int iv_wait_interest_kill(const struct iv_wait_interest *this, int
       sig);

DESCRIPTION
       iv_wait is an ivykis(3) wrapper around wait4(2), integrating process
       state change notification with the ivykis event loop.

       An ivykis application desiring process state change notifications
       registers a struct iv_wait_interest object by calling
       iv_wait_interest_register, after having initialised it with
       IV_WAIT_INTEREST_INIT and subsequently having filled in the ->pid,
       ->cookie and ->handler members.

       Alternatively, an ivykis application can use
       iv_wait_interest_register_spawn to atomically fork off a child process
       and register a struct iv_wait_interest for it.  In this context,
       'atomically' means that the call to iv_wait_interest_register_spawn
       will be serialised with respect to invocations of wait4(2), which
       closes the race where process state change notifications can occur and
       be delivered between forking off the child process and registering a
       struct iv_wait_interest for the child's pid.  The child process will
       run the function given by the iv_wait_interest_register_spawn argument
       fn, with argument cookie as its argument.

       Once a process state change occurs (as indicated by delivery of a
       SIGCHLD signal to the current process), iv_wait calls wait4(2) to
       return information about the process state change, looks up the
       returned process ID in the set of registered struct iv_wait_interest
       objects, and if there is a registered interest with a matching ->pid
       field, arranges for that object's callback function to be called in the
       thread that the object was registered in.

       Process state change notifications will continue to be delivered to the
       object's callback function until iv_wait_interest_unregister is called
       on the object or until a WIFEXITED or WIFSIGNALED status for this pid
       is returned by wait4(2).

       Delivery of a WIFEXITED or WIFSIGNALED status does not automatically
       unregister the object, this always needs to be done explicitly.

       Unregistering a struct iv_wait_interest object can only be done from
       the thread that that object was registered in, but within that thread,
       can safely be done from (and its underlying memory allocation can
       safely be freed from) its own callback function.

       Registering multiple struct iv_wait_interest objects for the same
       process ID will produce undefined behavior.

       To send a signal to a child process, use iv_wait_interest_kill.  This
       function will internally serialise with invocations of wait4(2), to
       avoid the race between sending a signal to a process and collecting a
       termination notification for that process (which makes its pid
       available for reuse).

       Internally, iv_wait is implemented using iv_signal(3) and iv_event(3).

SEE ALSO
       ivykis(3), iv_signal(3), iv_event(3), wait4(2)

ivykis                            2010-09-03                        iv_wait(3)