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G_EVENT(9) 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); struct g_event * g_alloc_event(int flag); void g_post_event_ep(g_event_t *func, void *arg, struct g_event *ep, ...); DESCRIPTION The GEOM framework has its own event queue to inform classes about im- portant 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 ar- guments 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 can- celed and then returns. The g_post_event_ep() function posts the event with a pre-allocated struct g_event. An event may be pre-allocated with g_alloc_event(). The g_cancel_event() function cancels all event(s) identified by ref. Cancellation is equivalent to calling the requested function with re- quested 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. g_alloc_event(): The argument flag has to be M_WAITOK or M_NOWAIT. The returned struct g_event * must be freed with g_free() if g_post_event_ep() is not called. RETURN VALUES The g_post_event() and g_waitfor_event() functions return 0 if success- ful; 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_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>. FreeBSD 14.3 July 23, 2021 G_EVENT(9)
NAME | SYNOPSIS | DESCRIPTION | RESTRICTIONS/CONDITIONS | RETURN VALUES | EXAMPLES | ERRORS | SEE ALSO | AUTHORS
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