SERIALIZER(9) BSD Kernel Developer's Manual SERIALIZER(9)NAME
lwkt_serialize_init, lwkt_serialize_enter, lwkt_serialize_adaptive_enter,
lwkt_serialize_try, lwkt_serialize_exit, lwkt_serialize_handler_enable,
lwkt_serialize_handler_disable, lwkt_serialize_handler_call,
lwkt_serialize_handler_try, ASSERT_SERIALIZED ASSERT_NOT_SERIALIZED —
generic low level serializer
SYNOPSIS
#include <sys/serialize.h>
void
lwkt_serialize_init(lwkt_serialize_t s);
void
lwkt_serialize_enter(lwkt_serialize_t s);
void
lwkt_serialize_adaptive_enter(lwkt_serialize_t s);
int
lwkt_serialize_try(lwkt_serialize_t s);
void
lwkt_serialize_exit(lwkt_serialize_t s);
void
lwkt_serialize_handler_enable(lwkt_serialize_t s);
void
lwkt_serialize_handler_disable(lwkt_serialize_t s);
void
lwkt_serialize_handler_call(lwkt_serialize_t s,
void (*func)(void *, void *), void *arg, void *frame);
int
lwkt_serialize_handler_try(lwkt_serialize_t s,
void (*func)(void *, void *), void *arg, void *frame);
ASSERT_SERIALIZED(s);
ASSERT_NOT_SERIALIZED(s);
DESCRIPTION
The serializer API provides a fast locked-bus-cycle-based serialization
facility that will serialize across blocking conditions. It is very sim‐
ilar to a lock but much faster for the common case.
This API was initially designed to be a replacement for SPL calls, but
may be used whenever a low level exclusive lock (serialization) and/or
interrupt/device interaction is required. Unlike tokens this serializa‐
tion is not safe from deadlocks nor is it recursive, and care must be
taken when using it. Note that tsleep(9) will not release a serializer
that is being held.
There are two primary facilities — the serializer facility itself and an
integrated non-stackable interrupt handler disablement facility used by
drivers.
lwkt_serialize_init(), lwkt_serialize_enter() and lwkt_serialize_exit()
respectively initialize, hold and release the serializer s.
lwkt_serialize_try() is a non-blocking version of lwkt_serialize_enter().
lwkt_serialize_adaptive_enter() is a special version of
lwkt_serialize_enter() which will try to spin a bit before the current
thread is put to sleep if the serializer s is contended. By default,
lwkt_serialize_adaptive_enter() favors spinning over sleeping. This
behavior can be changed by tuning the debug.serialize_bolimit and
debug.serialize_boround sysctl(8) variables. Note that
lwkt_serialize_adaptive_enter() is only available in SMP kernels.
lwkt_serialize_handler_disable(), lwkt_serialize_handler_enable() and
lwkt_serialize_handler_call() respectively disable, enable and call an
interrupt handler func for the serializer s. The arguments arg and frame
will be passed to the handler. lwkt_serialize_handler_try() is a non-
blocking version of lwkt_serialize_handler_call().
The ASSERT_SERIALIZED() and ASSERT_NOT_SERIALIZED() macros assert that
the serializer s is being held/not held.
RETURN VALUES
The lwkt_serialize_try() and lwkt_serialize_handler_try() functions
return 0 on success and 1 on failure.
FILES
The serializer itself is implemented in /sys/kern/lwkt_serialize.c. The
header file /sys/sys/serialize.h describes the public interface and the
structure of a serializer.
SEE ALSOcrit_enter(9), spinlock(9), zsleep(9)HISTORY
The serializer API first appeared in DragonFly 1.3.
AUTHORS
The serializer API was written by Matt Dillon. This manual page was
written by Hasso Tepper.
BSD April 10, 2010 BSD
