Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

g_waitfor_event(9) [freebsd man page]

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

Check Out this Related Man Page

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
Man Page