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 themselves, 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_WAITOKorM_NOWAIT. - The list of references has to end with a
NULLvalue.
- The argument flag has to be
M_WAITOKorM_NOWAIT. - The list of references has to end with a
NULLvalue. - 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.\n", arg);
return;
}
printf("Event with argument %p called.\n", arg);
}
ERRORS
Possible errors for the g_post_event()
function:
- [
ENOMEM] - The flag argument was set to
M_NOWAITand 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_NOWAITand 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>.