1.\" 2.\" Copyright (c) 2007 3.\" The DragonFly Project. All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in 13.\" the documentation and/or other materials provided with the 14.\" distribution. 15.\" 3. Neither the name of The DragonFly Project nor the names of its 16.\" contributors may be used to endorse or promote products derived 17.\" from this software without specific, prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 22.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 23.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 24.\" INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 25.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 26.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 27.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 28.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 29.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $DragonFly: src/share/man/man9/serializer.9,v 1.5 2008/05/15 09:21:40 swildner Exp $ 33.\" 34.Dd May 15, 2008 35.Os 36.Dt SERIALIZER 9 37.Sh NAME 38.Nm lwkt_serialize_init , 39.Nm lwkt_serialize_enter , 40.Nm lwkt_serialize_adaptive_enter , 41.Nm lwkt_serialize_try , 42.Nm lwkt_serialize_exit , 43.Nm lwkt_serialize_handler_enable , 44.Nm lwkt_serialize_handler_disable , 45.Nm lwkt_serialize_handler_call , 46.Nm lwkt_serialize_handler_try , 47.Nm IS_SERIALIZED 48.Nm ASSERT_SERIALIZED 49.Nm ASSERT_NOT_SERIALIZED 50.Nd generic low level serializer 51.Sh SYNOPSIS 52.In sys/serialize.h 53.Ft void 54.Fn lwkt_serialize_init "lwkt_serialize_t s" 55.Ft void 56.Fn lwkt_serialize_enter "lwkt_serialize_t s" 57.Ft void 58.Fn lwkt_serialize_adaptive_enter "lwkt_serialize_t s" 59.Ft int 60.Fn lwkt_serialize_try "lwkt_serialize_t s" 61.Ft void 62.Fn lwkt_serialize_exit "lwkt_serialize_t s" 63.Ft void 64.Fn lwkt_serialize_handler_enable "lwkt_serialize_t s" 65.Ft void 66.Fn lwkt_serialize_handler_disable "lwkt_serialize_t s" 67.Ft void 68.Fo lwkt_serialize_handler_call 69.Fa "lwkt_serialize_t s" 70.Fa "void (*func)(void *, void *)" 71.Fa "void *arg" 72.Fa "void *frame" 73.Fc 74.Ft int 75.Fo lwkt_serialize_handler_try 76.Fa "lwkt_serialize_t s" 77.Fa "void (*func)(void *, void *)" 78.Fa "void *arg" 79.Fa "void *frame" 80.Fc 81.Fn IS_SERIALIZED "s" 82.Fn ASSERT_SERIALIZED "s" 83.Fn ASSERT_NOT_SERIALIZED "s" 84.Sh DESCRIPTION 85The 86.Nm serializer 87API provides a fast locked-bus-cycle-based serialization facility 88that will serialize across blocking conditions. 89It is very similar to a lock but much faster for the common case. 90.Pp 91This API was initially designed to be a replacement for SPL calls, but 92may be used whenever a low level exclusive lock (serialization) and/or 93interrupt/device interaction is required. 94Unlike tokens this serialization is not safe from deadlocks nor is it 95recursive, and care must be taken when using it. 96Note that 97.Xr tsleep 9 98will not release a serializer that is being held. 99.Pp 100There are two primary facilities \(em the serializer facility itself and 101an integrated non-stackable interrupt handler disablement facility 102used by drivers. 103.Pp 104.Fn lwkt_serialize_init , 105.Fn lwkt_serialize_enter 106and 107.Fn lwkt_serialize_exit 108respectively initialize, hold and release the serializer 109.Fa s . 110.Fn lwkt_serialize_try 111is a non-blocking version of 112.Fn lwkt_serialize_enter . 113.Pp 114.Fn lwkt_serialize_adaptive_enter 115is a special version of 116.Fn lwkt_serialize_enter 117which will try to spin a bit before the current thread is put to sleep 118if the serializer 119.Fa s 120is contended. 121By default, 122.Fn lwkt_serialize_adaptive_enter 123favors spinning over sleeping. 124This behavior can be changed by tuning the 125.Va debug.serialize_bolimit 126and 127.Va debug.serialize_boround 128.Xr sysctl 8 129variables. 130Note that 131.Fn lwkt_serialize_adaptive_enter 132is only available in SMP kernels. 133.Pp 134.Fn lwkt_serialize_handler_disable , 135.Fn lwkt_serialize_handler_enable 136and 137.Fn lwkt_serialize_handler_call 138respectively disable, enable and call an interrupt handler 139.Fa func 140for the serializer 141.Fa s . 142The arguments 143.Fa arg 144and 145.Fa frame 146will be passed to the handler. 147.Fn lwkt_serialize_handler_try 148is a non-blocking version of 149.Fn lwkt_serialize_handler_call . 150.Pp 151The 152.Fn IS_SERIALIZED 153macro tests if the serializer 154.Fa s 155is being held. 156Similarly, the 157.Fn ASSERT_SERIALIZED 158and 159.Fn ASSERT_NOT_SERIALIZED 160macros assert that the serializer 161.Fa s 162is being held/not held. 163.Sh RETURN VALUES 164The 165.Fn lwkt_serialize_try 166and 167.Fn lwkt_serialize_handler_try 168functions return 0 on success and 1 on failure. 169.Sh FILES 170.Pa sys/kern/lwkt_serialize.c 171.Sh SEE ALSO 172.Xr crit_enter 9 , 173.Xr serialize_sleep 9 , 174.Xr spinlock 9 175.Sh HISTORY 176The 177.Nm serializer 178API first appeared in 179.Dx 1.3 . 180.Sh AUTHORS 181.An -nosplit 182The 183.Nm serializer 184API was written by 185.An Matt Dillon . 186This manual page was written by 187.An Hasso Tepper . 188