G_EVENT(9) BSD Kernel Developer's Manual G_EVENT(9)
NAME
g_post_event, g_waitfor_event, g_cancel_event -- GEOM events management
SYNOPSIS
#include <geom/geom.h>
int
g_post_event(g_event_t *func, void *arg, int flag, ...);
int
g_waitfor_event(g_event_t *func, void *arg, int flag, ...);
void
g_cancel_event(void *ref);
DESCRIPTION
The GEOM framework has its own event queue to inform classes about important events. The event queue can be also used by GEOM classes them-
selves, for example to work around some restrictions in the I/O path, where sleeping, heavy weight tasks, etc. are not permitted.
The g_post_event() function tells the GEOM framework to call function func with argument arg from the event queue. The flag argument is
passed to malloc(9) for memory allocations inside of g_post_event(). The only allowed flags are M_WAITOK and M_NOWAIT. The rest of the
arguments are used as references to identify the event. An event can be canceled by using any of the given references as an argument to
g_cancel_event(). The list of references has to end with a NULL value.
The g_waitfor_event() function is a blocking version of the g_post_event() function. It waits until the event is finished or canceled and
then returns.
The g_cancel_event() function cancels all event(s) identified by ref. Cancellation is equivalent to calling the requested function with
requested arguments and argument flag set to EV_CANCEL.
RESTRICTIONS
/CONDITIONS
g_post_event():
The argument flag has to be M_WAITOK or M_NOWAIT.
The list of references has to end with a NULL value.
g_waitfor_event():
The argument flag has to be M_WAITOK or M_NOWAIT.
The list of references has to end with a NULL value.
The g_waitfor_event() function cannot be called from an event, since doing so would result in a deadlock.
RETURN VALUES
The g_post_event() and g_waitfor_event() functions return 0 if successful; otherwise an error code is returned.
EXAMPLES
Example of a function called from the event queue.
void
example_event(void *arg, int flag)
{
if (flag == EV_CANCEL) {
printf("Event with argument %p canceled.
", arg);
return;
}
printf("Event with argument %p called.
", arg);
}
ERRORS
Possible errors for the g_post_event() function:
[ENOMEM] The flag argument was set to M_NOWAIT and there was insufficient memory.
Possible errors for the g_waitfor_event() function:
[EAGAIN] The event was canceled.
[ENOMEM] The flag argument was set to M_NOWAIT and there was insufficient memory.
SEE ALSO
geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9), g_bio(9), g_consumer(9), g_data(9), g_geom(9), g_provider(9),
g_provider_by_name(9), g_wither_geom(9)
AUTHORS
This manual page was written by Pawel Jakub Dawidek <pjd@FreeBSD.org>.
BSD
January 16, 2004 BSD