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g_post_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

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G_CONSUMER(9)						   BSD Kernel Developer's Manual					     G_CONSUMER(9)

NAME
g_new_consumer, g_destroy_consumer -- GEOM consumers management SYNOPSIS
#include <geom/geom.h> struct g_consumer * g_new_consumer(struct g_geom *gp); void g_destroy_consumer(struct g_consumer *cp); DESCRIPTION
A GEOM consumer is the backdoor through which a geom connects to another GEOM provider and through which I/O requests are sent. The g_new_consumer() function creates a new consumer on geom gp. Before using the new consumer, it has to be attached to a provider with g_attach(9) and opened with g_access(9). The g_destroy_consumer() function destroys the given consumer and cancels all related pending events. This function is the last stage of killing an unwanted consumer. RESTRICTIONS
/CONDITIONS g_new_consumer(): The geom gp has to have an orphan method defined. The topology lock has to be held. g_destroy_consumer(): The consumer must not be attached to a provider. The access count has to be 0. The topology lock has to be held. RETURN VALUES
The g_new_consumer() function returns a pointer to the newly created consumer. EXAMPLES
Create consumer, attach it to given provider, gain read access and clean up. void some_function(struct g_geom *mygeom, struct g_provider *pp) { struct g_consumer *cp; g_topology_assert(); /* Create new consumer on 'mygeom' geom. */ cp = g_new_consumer(mygeom); /* Attach newly created consumer to given provider. */ if (g_attach(cp, pp) != 0) { g_destroy_consumer(cp); return; } /* Open provider for reading through our consumer. */ if (g_access(cp, 1, 0, 0) != 0) { g_detach(cp); g_destroy_consumer(cp); return; } g_topology_unlock(); /* * Read data from provider. */ g_topology_lock(); /* Disconnect from provider (release access count). */ g_access(cp, -1, 0, 0); /* Detach from provider. */ g_detach(cp); /* Destroy consumer. */ g_destroy_consumer(cp); } SEE ALSO
geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9), g_bio(9), g_data(9), g_event(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
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