GLAST / LAT > DAQ and FSW > FSW > Doxygen Index> PBS / V2-12-1 > pbs / rhel4-32
#include <stdio.h>
#include <string.h>
#include <PBI/Ofs.h>
#include <PBS/PL.ih>
#include <PBS/LI.ih>
#include <PBS/TASK.h>
#include <PBS/TOC.h>
#include <TASK_pvtdefs.h>
#include <PBI/PTR.h>
#include <PBS/FORK.h>
Classes | |
union | _FORK_que |
Structure defining a FORK_que. More... | |
union | _FORK_que_head |
Structure defining a FORK_que_head. The FORK routines are set up to manage to types of ques, a simply linked list or a Priority List of ques. This is simply a union of the controlling list heads. More... | |
struct | _FORK_fcb |
Defines Fork Control Block containing the global information about the FORK que. More... | |
Typedefs | |
typedef union _FORK_que_head | FORK_que_head |
Typedef for a FORK_que_head. | |
typedef enum _FORK_msg_type | FORK_msg_type |
Typedef for enum FORK_msg_type. | |
Enumerations | |
enum | _FORK_msg_type { FORK_K_MSG_TYPE_USR = 0, FORK_K_MSG_TYPE_SYS = 1 } |
Distinguishes between the two types of messages, user or system. More... | |
Functions | |
int | FORK_fcb_sizeof (int nques) |
Returns the size, in bytes, of a FORK Control Block. | |
int | FORK_create (FORK_fcb *fcb, const struct _TASK_attr *attributes, FORK_cb_rtn def_handler, FORK_cb_prm ctx, FORK_cb_prm tmo_ctx, const TOC *tmo_toc, int nques, const FORK_que_cfg *que_cfg, FORK_type msg_type, FORK_msg_sys *msg_blks, int msg_cnt) |
Creates a FORK message que. | |
FORK_que * | FORK_que_get (FORK_fcb *fcb, int que_id) |
Returns a handle to the specified que. | |
int | FORK_destroy (FORK_fcb *fcb) |
Destroys a FORK que. | |
FORK_que_list | FORK_disable (FORK_fcb *fcb, FORK_que_list disable_list) |
Disables the servicing of the specified ques. | |
FORK_que_list | FORK_enable (FORK_fcb *fcb, FORK_que_list enable_list) |
Enables the servicing of the specified ques. | |
FORK_que_list | FORK_enabled (const FORK_fcb *fcb) |
Returns the enable/disabled state of the specified que. | |
int | FORK_qdisable (FORK_que *que) |
Disables the servicing of the specified que. | |
int | FORK_qenable (FORK_que *que) |
Enables the servicing of the specified que. | |
int | FORK_qenabled (const FORK_que *que) |
Returns the enable/disabled state of all ques. | |
int | FORK_qhead_modify (FORK_que *que, FORK_cb_modify modify, void *context) |
Sneaky way to modify the head (oldest) element on the specified FORK que. | |
int | FORK_qtail_modify (FORK_que *que, FORK_cb_modify modify, void *context) |
Sneaky way to modify the tail (newest) element on the specified FORK que. | |
int | FORK_qsys (FORK_que *que, FORK_cb_rtn handler, void *contents) |
Ques a message using the internal FORK message blocks. | |
int | FORK_qsysW (FORK_que *que, FORK_cb_rtn handler, void *contents) |
Ques a message using the internal FORK message blocks. | |
int | FORK_qsysW_toc (FORK_que *que, FORK_cb_rtn handler, void *contents, const TOC *tmo_toc) |
Ques a message using the internal FORK message blocks. | |
int | FORK_qusr (FORK_que *que, FORK_cb_rtn handler, FORK_msg_hdr *msg_hdr) |
Ques a user composed message. | |
int | FORK_resume (FORK_fcb *fcb) |
Resumes a previously suspended FORK task. | |
int | FORK_suspend (FORK_fcb *fcb) |
Suspends the FORK task. | |
int | FORK_join (FORK_fcb *fcb, int *exit_status) |
Waits until the FORK'd task is deleted. |
CVS $Id: FORK.c,v 1.13 2011/03/24 23:05:46 apw Exp $
1. The FORK routines allow user controller over memory allocation.
The msgQ routines allocate memory when a request to send a message is made. If no memory is available, the user may either have the call return with failure or block. Ignoring the 'return with failure option' a problem occurs when blocking is not an option, as in an interrupt service routine. The FORK routines allow the user to pre-allocate the message buffer before committing to servicing an interrupt. This ensures that the necessary resources are in hand.
2. The burden of creating the receiving task is taken on by the FORK_create() routine.
Since the metaphor of the FORK routines is to transparently fork the execution path, this seems more natural than manually creating an task/thread to handle the messages. In most cases, this is all the create task is going to do, ie pend on a message que and service the incominig messages.
3. The messsage to be queued is not copied twice as it is in the VxWorks routines (once when sending and once when receiving).
This is a direct consequence of allowing the user to do his own management of the message buffers. Many times memory allocation can be avoid altogether. All the FORK routines demand is two free 32 bit locations (one for a link management and the other for a dispatch routine). Both locations are used only when on the FORK que. Many times the user can find two free location in the piece of information being sent, thus avoiding allocation (and, more importantly, handling the case of failure to allocate) altogether.
4. The FORK routines offer the option of managing a number (up to 32) priority order ques.
This feature allows higher priority messages to be serviced first, effectively creating an out-of-band mechanism.
A good use for these would be a command receiver/command handler. Assuming the receiver and handler are in different threads, the receiver receives incoming commands, decides which FORK que they should be assigned to and the function that such be executed. The received packages this information along with the command parameters and ques it. The handler thread wakes out and executes the command.
This latter design choice has only a slight impact on performance, since, in theory, the dispatch routine could release the message memory earlier. However, given the single reader nature of the FORK utilities, only one such buffer can be outstanding at an given time. The truly concerned user can avoid this limitation by using only message buffers that he manages.
int test_fork (void) { FORK_fcb *fcb; FORK_que *que; int size; int exit_status; / * Allocate 10 message blocks for the FORK ques internal pool * / FORK_msg_sys msg_blks[10]; int msg_blk_cnt = sizeof (msg_blks) / sizeof (*msg_blks); size = FORK_fcb_sizeof (1); / * Size of Fork Control Block * / fcb = (FORK_fcb *) MBA_alloc (size); / * Allocate the memory for it * / / * Create the fork que * / status = FORK_create (fcb, / * Fork Control Block to init * / NULL, / * Use default task attributes * / normalPrint, / * Default handling routine * / forkParameter, / * Parameter passed to handler * / forkTmoParameter, / * Parameter passed if timeout * / TOC_FOREVER, / * How long to pend before tmo * / 1, / * One internal FORK que * / NULL, / * Individual que cfg's * / FORK_K_TYPE_PENDING_WTO,, / * FIFO style blocking when * / / * allocating system messges * / msg_blks, / * A source of message blocks * / msg_blk_cnt) / * Number of messge blocks * / / * | Retrieve the que to post messages to. In this example the FORK | routines were initialized to support only a single que, so the | que to be located in que = 0 / que = FORK_get_que (fcb, 0); / * Post a series of messages to this que * / status = FORK_qsysW (que, NULL, "Hello World\n"); status = FORK_qsysW (que, boldPrint, "Goodbye World\n"); status = FORK_qsysW (que, winddown, "Killing FORK'd task\n"); status = FORK_join (que, &exit_status); / * | All done, kill the que. Note that this call blocks until the | the FORK'd task has completed its work. / status = FORK_destroy (fcb); free (fcb); return 0; } int normalPrint (void *parameter, FORK_msg_sys *msg) { fputs (msg->contents); return FORK_C_CONTINUE; } int boldPrint (void *parameter, FORK_msg_sys *msg) { printf ("%s", BOLD_ESC_SEQUENCE); fputs (msg->contents); printf ("%s", NORMAL_ESC_SEQUENCE); return FORK_C_CONTINUE; } int winddown (void *parameter, FORK_msg_sys *msg) { fputs (msg->contents); fflush (stdout); / * Indicate that this is it * / return 1; }
enum _FORK_msg_type |
int FORK_create | ( | FORK_fcb * | fcb, | |
const struct _TASK_attr * | attributes, | |||
FORK_cb_rtn | def_handler, | |||
FORK_cb_prm | ctx, | |||
FORK_cb_prm | tmo_ctx, | |||
const TOC * | tmo_toc, | |||
int | nques, | |||
const FORK_que_cfg * | que_cfg, | |||
FORK_type | msg_type, | |||
FORK_msg_sys * | msg_blks, | |||
int | msg_cnt | |||
) |
Creates a FORK message que.
fcb | The FORK Control Block to initialize | |
attributes | The attributes to use when creating the FORK servicing task. | |
def_handler | The address of a default FORK handler. This routine will be called back in one of two circumstances. |
ctx | Parameter passed transparently to the user's callback handler, except in the case of a timeout. | |
tmo_ctx | Parameter passed transparently to the user's callback routine in case of a timeout. The user may use this parameter to distinguish a timeout condition from a normal message. (The message block will also be NULL in this case.) | |
tmo_toc | Timeout control specification. This is used when a message is being pended for. If this value is TOC_FOREVER, the pend is indefinite. |
nques | If specified as 0 or 1, a single non-prioritized que is used. If specified as >1, multiple prioritized ques are used. que_cfg configures each of the ques. | |
que_cfg | An array of que configuration blocks. If nques is specified as 0 or 1, this parameter is ignored. If the callback routine is specified as NULL for any individual que configuration, the default callback handler is used. | |
msg_type | The blocking type to use when attempting allocate a message from the system queue. There are three blocking styles. |
msg_blks | A source of internal message blocks. This may be specified as NULL and is ignored if msg_cnt is specified as 0. |
msg_cnt | The number of msg_blks. This may be specified as 0. In this case no system message pool is created and the values of the parameters msg_type and msg_blks are ignored. |
References _FORK_fcb::cfg, _FORK_que_cfg::ctx, _FORK_fcb::def, _FORK_fcb::enabled, _FORK_fcb::freelist, _FORK_que_cfg::handler, _FORK_que_head::li, LI_init(), LI_K_TYPE_PENDING_WTO, _FORK_fcb::msg_beg, _FORK_fcb::msg_cnt, _FORK_fcb::msg_end, _FORK_fcb::nques, _FORK_fcb::pend, _FORK_que_head::pl, PL_init(), PL_K_TYPE_PENDING_WTO, PL_SIZEOF, _FORK_fcb::rw, RW_init(), RW_K_TYPE_PENDING, TASK_spawn(), TASK_tcb_sizeof(), _FORK_fcb::tcb, _FORK_que_cfg::tmo_ctx, _FORK_fcb::tmo_toc, _FORK_fcb::toc_buf, TOC_IS_FOREVER, and TOC_IS_NOWAIT.
int FORK_destroy | ( | FORK_fcb * | fcb | ) |
Destroys a FORK que.
fcb | The Fork Control Block of the FORK que to destroy |
The usual method of winding down the FORK task is for the parent task to send a QUIT message to the FORK'd task. The parent task then calls FORK_join, which block until the FORK'd task exits. The FORK'd task performs any necessary clean-up then returns a non-zero status code from the callback routine. This causes the FORK'd task to delete itself, allowing the FORK_join() call to complete.
References _FORK_fcb::freelist, _FORK_que_head::li, LI_destroy(), _FORK_fcb::msg_cnt, _FORK_fcb::nques, _FORK_fcb::pend, _FORK_que_head::pl, PL_destroy(), _FORK_fcb::rw, and RW_destroy().
int FORK_disable | ( | FORK_fcb * | fcb, | |
FORK_que_list | disable_list | |||
) |
Disables the servicing of the specified ques.
fcb | The FORK Control Block | |
disable_list | The list of ques to disable |
References _FORK_fcb::enabled, _FORK_que_head::li, LI__disable(), _PL_ctl::mcfg, _FORK_fcb::nques, _FORK_fcb::pend, _FORK_que_head::pl, _FORK_fcb::rw, RW__lock(), and RW__unlock().
Referenced by FORK_qdisable().
int FORK_enable | ( | FORK_fcb * | fcb, | |
FORK_que_list | enable_list | |||
) |
Enables the servicing of the specified ques.
fcb | The FORK Control Block | |
enable_list | The list of ques to enable |
References _FORK_fcb::enabled, _FORK_que_head::li, LI__enable(), _PL_ctl::mcfg, _FORK_fcb::nques, _FORK_fcb::pend, _FORK_que_head::pl, PL__wake(), _FORK_fcb::rw, RW__lock(), and RW__unlock().
Referenced by FORK_qenable().
FORK_que_list FORK_enabled | ( | const FORK_fcb * | fcb | ) |
Returns the enable/disabled state of the specified que.
fcb | The FORK control block |
References _FORK_fcb::enabled, _FORK_que_head::li, LI__enabled(), _FORK_fcb::nques, and _FORK_fcb::pend.
FORK_fcb_sizeof | ( | int | nques | ) |
Returns the size, in bytes, of a FORK Control Block.
nques | The number of internal ques to be supported |
The FORK routines are capable of supporting multiple prioritized internal ques. This is done by specifying nques to be greater than 1.
References PL_SIZEOF, and TASK_tcb_sizeof().
int FORK_join | ( | FORK_fcb * | fcb, | |
int * | exit_status | |||
) |
Waits until the FORK'd task is deleted.
fcb | The Fork Control Block | |
exit_status | Returned as the exit status of the FORK'd task. |
The usual method of winding down the FORK task is for the parent task to send a QUIT message to the FORK'd task. The parent task then calls FORK_join, which block until the FORK'd task exits. The FORK'd task performs any necessary clean-up then returns a non-zero status code from the callback routine. (This status code is returned to the user as exit_status.) This causes the FORK'd task to delete itself, allowing the FORK_join() call to complete. The user is then free to call FORK_destroy() to return the resources garnered by the FORK fcb.
Note that the exit_status may be returned as any non-zero 32-bit value. This includes returning a pointer to a structure which may contain additional information. If one does this, one must be careful to ensure that the memory is viable after task deletion. For instance, don't return pointers to things on the stack.
References TASK_join(), and _FORK_fcb::tcb.
int FORK_qdisable | ( | FORK_que * | que | ) |
Disables the servicing of the specified que.
0,if | the specified que was not originally enabled !=0, if the specified que was previously enabled |
que | The FORK que to disable |
References FORK_disable(), _PL_que::id, _FORK_que::pl, and PL_LIST.
int FORK_qenable | ( | FORK_que * | que | ) |
Enables the servicing of the specified que.
0,if | the specified que was not originally enabled !=0, if the specified que was previously enabled |
que | The FORK que to enable |
References FORK_enable(), _PL_que::id, _FORK_que::pl, and PL_LIST.
int FORK_qenabled | ( | const FORK_que * | que | ) |
Returns the enable/disabled state of all ques.
= | 0 if the queue was previously disabled != 0 if the queue was previously enabled |
que | The que to query |
References _FORK_fcb::enabled, _PL_que::id, _FORK_que_head::li, LI__enabled(), _FORK_fcb::nques, _FORK_fcb::pend, _FORK_que::pl, and PL_LIST.
int FORK_qhead_modify | ( | FORK_que * | que, | |
FORK_cb_modify | modify, | |||
void * | context | |||
) |
Sneaky way to modify the head (oldest) element on the specified FORK que.
que | The target fork que. | |
modify | A callback handler used to modify the que element. The return value of this callback routine is the return value of FORK_qhead_modify. |
context | A user provided context parameter. |
int FORK_qsys | ( | FORK_que * | que, | |
FORK_cb_rtn | handler, | |||
void * | contents | |||
) |
Ques a message using the internal FORK message blocks.
que | The target fork que. | |
handler | A callback handler. This may be specified as NULL, in which case, the default handler established by FORK_create(), will handle the message. | |
contents | A single 32-bit value representing the message contents. |
Note that because the message is internally allocated it may be possible that this list is exhausted. This version of the routine returns immediately with failure if the list is exhausted. See FORK_qsysW() or FORK_qsysW_toc for wait forever and wait with a timeout versions
References _FORK_msg_sys::contents, FORK_K_MSG_TYPE_SYS, _FORK_fcb::freelist, _FORK_msg_sys::hdr, and LI__remove().
int FORK_qsysW | ( | FORK_que * | que, | |
FORK_cb_rtn | handler, | |||
void * | contents | |||
) |
Ques a message using the internal FORK message blocks.
que | The target fork que. | |
handler | A callback handler. This may be specified as NULL, in which case, the default handler established by FORK_create(), will handle the message. | |
contents | A single 32-bit value representing the message contents. |
Note that because the message is internally allocated it may be possible that this list is exhausted. This version of the routine waits indefinitely until a message becomes available. See FORK_qsys() or FORK_qsysW_toc for no wait and wait with timeout versions.
References _FORK_msg_sys::contents, FORK_K_MSG_TYPE_SYS, _FORK_fcb::freelist, _FORK_msg_sys::hdr, and LI__removeW().
int FORK_qsysW_toc | ( | FORK_que * | que, | |
FORK_cb_rtn | handler, | |||
void * | contents, | |||
const TOC * | tmo_toc | |||
) |
Ques a message using the internal FORK message blocks.
que | The target fork que. | |
handler | A callback handler. This may be specified as NULL, in which case, the default handler established by FORK_create(), will handle the message. | |
contents | A single 32-bit value representing the message contents. | |
tmo_toc | A timeout control structure. This is used when no system message blocks available. The values TOC_NOWAIT and TOC_FOREVER can be used here. The information in this structure is copied, so the user may free the memory after the call. |
Note that because the message is internally allocated it may be possible that this list is exhausted. A timeout parameter is provided to handle this situation. See FORK_qsys() or FORK_qsysW for no wait and wait forever versions.
References _FORK_msg_sys::contents, FORK_K_MSG_TYPE_SYS, _FORK_fcb::freelist, _FORK_msg_sys::hdr, and LI__removeW_toc().
int FORK_qtail_modify | ( | FORK_que * | que, | |
FORK_cb_modify | modify, | |||
void * | context | |||
) |
Sneaky way to modify the tail (newest) element on the specified FORK que.
que | The target fork que. | |
modify | A callback handler used to modify the que element. The return value of this callback routine is the return value of FORK_qhead_modify. |
context | A user provided context parameter. |
Returns a handle to the specified que.
fcb | The FORK Control Block | |
que_id | The ID of the que |
References _FORK_que_head::li, _FORK_fcb::nques, _FORK_fcb::pend, _FORK_que_head::pl, and PL__que_get().
int FORK_qusr | ( | FORK_que * | que, | |
FORK_cb_rtn | handler, | |||
FORK_msg_hdr * | msg_hdr | |||
) |
Ques a user composed message.
que | The target fork que. | |
handler | A callback handler. This may be specified as NULL, in which case, the default handler established by FORK_create(), will handle the message. | |
msg_hdr | Pointer to the message to que. It is mandatory that all queued messages are prefaced by a standard message header block |
For the extra work involved in using this routine, the user gets to control his own memory allocation and the exact contents of the message. This means that there is almost no case, other than an internal corruption, under which this routine can fail.
References FORK_K_MSG_TYPE_USR.
int FORK_resume | ( | FORK_fcb * | fcb | ) |
Resumes a previously suspended FORK task.
fcb | The FORK Control Block |
References TASK_resume(), and _FORK_fcb::tcb.
int FORK_suspend | ( | FORK_fcb * | fcb | ) |
Suspends the FORK task.
fcb | The FORK Control Block |
References TASK_suspend(), and _FORK_fcb::tcb.