RUMP_LWPROC(3)						   BSD Library Functions Manual 					    RUMP_LWPROC(3)

NAME

     rump_lwproc -- rump process/lwp management

LIBRARY

     rump kernel (librump, -lrump)

SYNOPSIS

     #include <rump/rump.h>

     int
     rump_pub_lwproc_rfork(int flags);

     int
     rump_pub_lwproc_newlwp(pid_t pid);

     void
     rump_pub_lwproc_switch(struct lwp *l);

     void
     rump_pub_lwproc_releaselwp();

     struct lwp *
     rump_pub_lwproc_curlwp();

DESCRIPTION

     In a normal operating system model a process is a resource container and a thread (lwp) is the execution context.	Every lwp is associated
     with exactly one process, and a process is associated with one or more lwps.  The current lwp (curlwp) indicates the current process and
     determines which resources, such as UID/GID, current working directory, and file descriptor table, are currently used.  These basic princi-
     ples apply to rump kernels as well, but since rump uses the host's thread and process context directly, the rules for how thread context is
     determined are different.

     In the rump model, each host thread (pthread) is either bound to a rump kernel lwp or accesses the rump kernel with an implicit thread con-
     text associated with pid 1.  An implicit thread context is created every time the rump kernel is entered and disbanded upon exit.	While con-
     venient for occasional calls, creating an implicit thread uses a shared resource which can become highly contended in a multithreaded situa-
     tion.  It is therefore recommended that dedicated threads are created.

     The association between host threads and the rump kernel curlwp is left to the caller.  It is possible to create a dedicated host thread for
     every rump kernel lwp or multiplex them on top of a single host thread.  After rump lwps have been created, switching curlwp is very cheap --
     faster than a thread context switch on the host.  In case multiple lwps/processes are created, it is the caller's responsibility to keep
     track of them and release them when they are no longer necessary.	Like other rump kernel resources, procs/lwps will be released when the
     process hosting the rump kernel exits.

     rump_pub_lwproc_rfork()
	   Create a process, one lwp inside it and set curlwp to the new lwp.  The flags parameter controls how file descriptors are inherited
	   from the parent.  By default (flags=0) file descriptors are shared.	Other options are:

	   RUMP_RFFDG	  Copy file descriptors from parent.  This is what fork(2) does.

	   RUMP_RFCFDG	  File descriptors neither copied nor shared, i.e. new process does not have access to the parent's file descriptors.

	   This routine returns 0 for success or an errno indicating the reason for failure.  The new process id can be retrieved in the normal
	   fashion by calling rump_sys_getpid().

     rump_pub_lwproc_newlwp(pid)
	   Create a new lwp attached to the process specified by pid.  Sets curlwp to the new lwp.  This routine returns 0 for success or an errno
	   indicating the reason for failure.

     rump_pub_lwproc_switch(l)
	   Sets curlwp to l.  In case the new thread is associated with a different process than the current one, the process context is also
	   switched.  The special value NULL sets curlwp to implicit context.  Switching to an already running lwp, i.e. attempting to use the
	   same curlwp in two host threads simultaneously causes a fatal error.

     rump_pub_lwproc_releaselwp()
	   Release curlwp and set curlwp to context.  In case curlwp was the last thread inside the current process, the process container is also
	   released.  Calling this routine without a dedicated curlwp is a fatal error.

     rump_pub_lwproc_curlwp()
	   Returns curlwp or NULL if the current context is an implicit context.

SEE ALSO

     getpid(2), rump(3)

HISTORY

     rump_lwproc first appeared in NetBSD 6.0.

BSD
								  January 2, 2011							       BSD