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$FreeBSD: releng/11.0/share/man/man9/g_event.9 267936 2014-06-26 21:44:30Z bapt $
.Dd January 16, 2004 .Dt G_EVENT 9 .Os .Sh NAME .Nm g_post_event , .Nm g_waitfor_event , .Nm g_cancel_event .Nd "GEOM events management" .Sh SYNOPSIS n geom/geom.h .Ft int .Fn g_post_event "g_event_t *func" "void *arg" "int flag" ... .Ft int .Fn g_waitfor_event "g_event_t *func" "void *arg" "int flag" ... .Ft void .Fn g_cancel_event "void *ref" .Sh 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.
p The .Fn g_post_event function tells the GEOM framework to call function .Fa func with argument .Fa arg from the event queue. The .Fa flag argument is passed to .Xr malloc 9 for memory allocations inside of .Fn g_post_event . The only allowed flags are .Dv M_WAITOK and .Dv 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 .Fn g_cancel_event . The list of references has to end with a .Dv NULL value.
p The .Fn g_waitfor_event function is a blocking version of the .Fn g_post_event function. It waits until the event is finished or canceled and then returns.
p The .Fn g_cancel_event function cancels all event(s) identified by .Fa ref . Cancellation is equivalent to calling the requested function with requested arguments and argument .Fa flag set to .Dv EV_CANCEL . .Sh RESTRICTIONS/CONDITIONS .Fn g_post_event : l -item -offset indent t The argument .Fa flag has to be .Dv M_WAITOK or .Dv M_NOWAIT . t The list of references has to end with a .Dv NULL value. .El
p .Fn g_waitfor_event : l -item -offset indent t The argument .Fa flag has to be .Dv M_WAITOK or .Dv M_NOWAIT . t The list of references has to end with a .Dv NULL value. t The .Fn g_waitfor_event function cannot be called from an event, since doing so would result in a deadlock. .El .Sh RETURN VALUES The .Fn g_post_event and .Fn g_waitfor_event functions return 0 if successful; otherwise an error code is returned. .Sh EXAMPLES Example of a function called from the event queue. d -literal -offset indent 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); } .Ed .Sh ERRORS Possible errors for the .Fn g_post_event function: l -tag -width Er t Bq Er ENOMEM The .Fa flag argument was set to .Dv M_NOWAIT and there was insufficient memory. .El
p Possible errors for the .Fn g_waitfor_event function: l -tag -width Er t Bq Er EAGAIN The event was canceled. t Bq Er ENOMEM The .Fa flag argument was set to .Dv M_NOWAIT and there was insufficient memory. .El .Sh SEE ALSO .Xr geom 4 , .Xr DECLARE_GEOM_CLASS 9 , .Xr g_access 9 , .Xr g_attach 9 , .Xr g_bio 9 , .Xr g_consumer 9 , .Xr g_data 9 , .Xr g_geom 9 , .Xr g_provider 9 , .Xr g_provider_by_name 9 , .Xr g_wither_geom 9 .Sh AUTHORS .An -nosplit This manual page was written by .An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org .