procmgr_event_notify()

Ask to be notified of system-wide events

Synopsis:

#include <sys/procmgr.h>

int procmgr_event_notify
            ( unsigned flags,
              const struct sigevent * event );

Arguments:

flags

Flags currently defined in <sys/procmgr.h> are:

PROCMGR_EVENT_DAEMON_DEATH -- notify the caller when any process in session 1 dies. This is most useful for watching for the death of daemon processes that use procmgr_daemon() to put themselves in session 1 as well as close and redirect file descriptors. As a result of this closing and redirecting, the death of daemons are difficult to detect otherwise.

Notification is via the given event, so no information is provided as to which process died. Once you've received the event, you'll need to do something else to find out if processes you care about had died. You can do this by walking through the list of all processes, looking for specific process IDs or process names. If you don't find one, then it has died. The sample code below demonstrates how this can be done.

PROCMGR_EVENT_PATHSPACE -- notify the caller when a resource manager adds or removes an entry (i.e. mountpoint) to or from the pathname space. This is generally associated with resource manager calls to resmgr_attach() and resmgr_detach(). Terminating a resource manager process also generates this event if the mouthpoints have not been detached.

This flag was added in the QNX Momentics 6.3.0 SP2.
PROCMGR_EVENT_SYNC -- notify the caller of any calls to sync() the filesystems.

Setting flags to 0 (zero) unarms the event.

event

A pointer to a sigevent structure that specifies how you want to notified.

/*
 * This demonstrates procmgr_event_notify() with the 
 * PROCMGR_DAEMON_DEATH flag. This flag allows you to 
 * be notified if any process in session 1 dies.  
 * Daemons are processes that do things that make
 * their death hard to detect (they become daemons by calling
 * procmgr_daemon()).  One of the things that happens is that
 * daemons end up in session 1.  Hence, the usefulness of the
 * PROCMGR_DAEMON_DEATH flag.
 *
 * When you are notified, you're not told who died.
 * It's up to you to know who should be running.  Once notified,
 * you could then walk through the list of which processes are
 * still running and see if all the expected processes are still
 * running. If you know the process id of the processes you
 * are watching out for then this is easiest.  If you don't know
 * the process id then your next option may be by process name.
 * The code below does a lookup by process name.
 */

#include <devctl.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/neutrino.h>
#include <sys/procfs.h>
#include <sys/procmgr.h>

static int check_if_running( char *process );

#define DAEMON_DIED_CODE   (_PULSE_CODE_MINAVAIL)

struct dinfo_s {
    procfs_debuginfo    info;
    char                pathbuffer[PATH_MAX];
};

int
main( int argc, char **argv )
{
    char            *daemon_to_watch;
    int             chid, coid, rcvid;
    struct sigevent event;
    struct _pulse   msg;
    
    if (argc != 2) {
        printf( "use: %s process_to_watch_for\n", argv[0] );
        exit( EXIT_FAILURE );
    }
    
    daemon_to_watch = argv[1];   /* the process to watch for */
    
    chid = ChannelCreate( 0 );
    coid = ConnectAttach( 0, 0, chid, _NTO_SIDE_CHANNEL, 0 );
    SIGEV_PULSE_INIT( &event, coid, SIGEV_PULSE_PRIO_INHERIT,
                      DAEMON_DIED_CODE, 0 );

    /*
     * Ask to be notified via a pulse whenever a 
     * daemon process dies
     */
     
    if (procmgr_event_notify( PROCMGR_EVENT_DAEMON_DEATH, 
                              &event ) == -1) {
        fprintf( stderr, "procmgr_event_notify() failed" );
        exit( EXIT_FAILURE );
    }

    while (1) {
        rcvid = MsgReceive( chid, &msg, sizeof(msg), NULL );
        if (rcvid != 0) {
            /* not a pulse; could be an unexpected message or
               error */
            exit( EXIT_FAILURE );
        }
        
        if (check_if_running( daemon_to_watch ) == 0)
            printf( "%s is no longer running\n", daemon_to_watch);
    }    
    return 0;
}

/*
 * check_if_running - This will walk through all processes 
 * to see if this particular one is still running.
 */
 
static int
check_if_running( char *process )
{
    DIR             *dirp;
    struct dirent   *dire;
    char            buffer[20];
    int             fd, status;
    pid_t           pid;
    struct dinfo_s  dinfo;
    
    if ((dirp = opendir( "/proc" )) == NULL) {
        perror( "Could not open '/proc'" );
        return -1;
    }
    while (1) {
        if ((dire = readdir( dirp )) == NULL)
            break;
        if (isdigit( dire->d_name[0] )) {
            pid = strtoul( dire->d_name, NULL, 0 );
    
            sprintf( buffer, "/proc/%d/as", pid );
            if ((fd = open( buffer, O_RDONLY )) != NULL) {
                status = devctl( fd, DCMD_PROC_MAPDEBUG_BASE,
                                 &dinfo, sizeof(dinfo), NULL );
                if (status == EOK) {
                    if (!strcmp( process,
                                 basename( dinfo.info.path ) ))
                    {
                        closedir (dirp);

                        /* You should close fd to prevent memory leaking */
                        close(fd); 
                       
                        return 1;
                    }
                } /* else some errors are expected, e.g. procnto
                     has no MAPDEBUG info and there is a timing
                     issue  with getting info on the process
                     that died, ignore errors */
                close( fd );
            }
        }
    }
    closedir( dirp );
    return 0;
}

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

procmgr_event_notify

procmgr_event_notify()

Synopsis:

Arguments:

Library:

Description:

Returns:

Examples:

Classification:

See also: