illumos: manual page: door_server

DOOR_SERVER_CREATE(3C) Standard C Library Functions DOOR_SERVER_CREATE(3C)

NAME

door_server_create - specify an alternative door server thread creation
function

SYNOPSIS

cc -mt [ flag... ] file... [ library... ]
#include <door.h>

void (*)(door_info_t *) door_server_create(void (*create_proc)(door_info_t *));

DESCRIPTION

Normally, the doors library creates new door server threads in response
to incoming concurrent door invocations automatically. There is no pre-
defined upper limit on the number of server threads that the system
creates in response to incoming invocations (1 server thread for each
active door invocation). These threads are created with the default
thread stack size and POSIX (see standards(7)) threads cancellation
disabled. The created threads also have the THR_BOUND | THR_DETACHED
attributes for Solaris threads and the PTHREAD_SCOPE_SYSTEM |
PTHREAD_CREATE_DETACHED attributes for POSIX threads. The signal
disposition, and scheduling class of the newly created thread are
inherited from the calling thread (initially from the thread calling
door_create(), and subsequently from the current active door server
thread).

The door_server_create() function allows control over the creation of
server threads needed for door invocations. The procedure create_proc is
called every time the available server thread pool is depleted. In the
case of private server pools associated with a door (see the DOOR_PRIVATE
attribute in door_create()), information on which pool is depleted is
passed to the create function in the form of a door_info_t structure.
The di_proc and di_data members of the door_info_t structure can be used
as a door identifier associated with the depleted pool. The create_proc
procedure may limit the number of server threads created and may also
create server threads with appropriate attributes (stack size, thread-
specific data, POSIX thread cancellation, signal mask, scheduling
attributes, and so forth) for use with door invocations.

The overall amount of data and argument descriptors that can be sent
through a door is limited by both the server thread's stack size and by
the parameters of the door itself. See door_setparam(3C).

The specified server creation function should create user level threads
using thr_create() with the THR_BOUND flag, or in the case of POSIX
threads, pthread_create() with the PTHREAD_SCOPE_SYSTEM attribute. The
server threads make themselves available for incoming door invocations on
this process by issuing a door_return(NULL, 0, NULL, 0). In this case,
the door_return() arguments are ignored. See door_return(3C) and
thr_create(3C).

The server threads created by default are enabled for POSIX thread
cancellations which may lead to unexpected thread terminations while
holding resources (such as locks) if the client aborts the associated
door_call(). See door_call(3C). Unless the server code is truly
interested in notifications of client aborts during a door invocation and
is prepared to handle such notifications using cancellation handlers,
POSIX thread cancellation should be disabled for server threads using
pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL). If all doors are
created with the DOOR_NO_CANCEL flag (see door_create(3C)), the threads
will never be cancelled by an aborted door_call() call

The create_proc procedure need not create any additional server threads
if there is at least one server thread currently active in the process
(perhaps handling another door invocation) or it may create as many as
seen fit each time it is called. If there are no available server threads
during an incoming door invocation, the associated door_call() blocks
until a server thread becomes available. The create_proc procedure must
be MT-Safe.

RETURN VALUES

Upon successful completion, door_server_create() returns a pointer to the
previous server creation function. This function has no failure mode (it
cannot fail).

EXAMPLES

Example 1: Creating door server threads.

The following example creates door server threads with cancellation
disabled and an 8k stack instead of the default stack size:

#include <door.h>
#include <pthread.h>
#include <thread.h>

void *
my_thread(void *arg)
{
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
door_return(NULL, 0, NULL, 0);
}
void
my_create(door_info_t *dip)
{
thr_create(NULL, 8192, my_thread, NULL,
THR_BOUND | THR_DETACHED, NULL);
}
main()
{
(void)door_server_create(my_create);
...
}

ATTRIBUTES