diff options
| -rw-r--r-- | share/man/man9/Makefile | 6 | ||||
| -rw-r--r-- | share/man/man9/mi_switch.9 | 141 |
2 files changed, 145 insertions, 2 deletions
diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile index fc02edb..bbfe7df 100644 --- a/share/man/man9/Makefile +++ b/share/man/man9/Makefile @@ -1,8 +1,9 @@ -# $Id: Makefile,v 1.23 1997/03/22 19:46:40 mpp Exp $ +# $Id: Makefile,v 1.24 1997/03/22 20:06:58 mpp Exp $ MAN9= MD5.9 at_shutdown.9 at_fork.9 at_exit.9 boot.9 cd.9 copy.9 \ devfs_add_devswf.9 \ - devfs_link.9 fetch.9 ifnet.9 intro.9 inittodr.9 panic.9 psignal.9 \ + devfs_link.9 fetch.9 ifnet.9 intro.9 inittodr.9 mi_switch.9 \ + panic.9 psignal.9 \ resettodr.9 rtalloc.9 rtentry.9 scsiconf.9 sd.9 sleep.9 spl.9 st.9 \ store.9 style.9 time.9 timeout.9 uio.9 \ vnode.9 vget.9 vput.9 vref.9 vrele.9 VOP_ABORTOP.9 VOP_ACCESS.9 \ @@ -24,6 +25,7 @@ MLINKS+= at_shutdown.9 rm_at_shutdown.9 MLINKS+= at_exit.9 rm_at_exit.9 MLINKS+= at_fork.9 rm_at_fork.9 MLINKS+= ifnet.9 ifaddr.9 ifnet.9 ifqueue.9 ifnet.9 if_data.9 +MLINKS+= mi_switch.9 cpu_switch.9 MLINKS+= psignal.9 pgsignal.9 psignal.9 gsignal.9 MLINKS+= rtalloc.9 rtalloc_ign.9 rtalloc.9 rtalloc1.9 MLINKS+= sleep.9 tsleep.9 sleep.9 wakeup.9 diff --git a/share/man/man9/mi_switch.9 b/share/man/man9/mi_switch.9 new file mode 100644 index 0000000..2fc23c6 --- /dev/null +++ b/share/man/man9/mi_switch.9 @@ -0,0 +1,141 @@ +.\" $NetBSD: ctxsw.9,v 1.2 1996/12/02 00:11:31 tls Exp $ +.\" +.\" Copyright (c) 1996 The NetBSD Foundation, Inc. +.\" All rights reserved. +.\" +.\" This code is derived from software contributed to The NetBSD Foundation +.\" by Paul Kranenburg. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the NetBSD +.\" Foundation, Inc. and its contributors. +.\" 4. Neither the name of The NetBSD Foundation nor the names of its +.\" contributors may be used to endorse or promote products derived +.\" from this software without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS +.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED +.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE +.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +.\" POSSIBILITY OF SUCH DAMAGE. +.\" +.Dd Nov 24, 1996 +.Dt mi_switch 9 +.Os FreeBSD +.Sh NAME +.Nm mi_switch , +.Nm cpu_switch +.Nd switch to another process context +.Sh SYNOPSIS +.Ft void +.Fn mi_switch "void" +.Ft void +.Fn cpu_switch "void" +.Sh DESCRIPTION +The +.Fn mi_switch +function implements the machine independent prelude to a process context +switch. It is called from only a few distinguished places in the kernel +code as a result of the principle of non-preemtable kernel mode execution. +The three major uses of +.Nm +can be enumerated as follows: +.Bl -enum -offset indent +.It +from within +.Xr sleep 9 , and +.Xr tsleep 9 +when the current process +voluntarily relinquishes the CPU to wait for some resource to become +available. +.It +after handling a trap +.Pq e.g. a system call, device interrupt +when the kernel prepares a return to user-mode execution. This case is +typically handled by machine dependent trap-handling code after detection +of a change in the signal disposition of the current process, or when a +higher priority process might be available to run. The latter event is +communicated by the machine independent scheduling routines by calling +the machine defined +.Fn need_resched "void" . +.It +in the signal handling code +.Pq see Xr issignal 9 +if a signal is delivered that causes a process to stop. +.El +.Pp +.Fn mi_switch +records the amount of time the current process has been running in the +process structure and checks this value against the CPU time limits +allocated to the process +.Pq see Xr getrlimit 2 . +Exceeding the soft limit results in a +.Dv SIGXCPU +signal to be posted to the process, while exceeding the hard limit will +cause a +.Dv SIGKILL . +After these administrative tasks are done, +.Fn mi_switch +hands over control to the machine dependent routine +.Fn cpu_switch "void" , +which will perform the actual process context switch. +.Pp +.Fn cpu_switch +will make a choice amongst the processes which are ready to run from a +priority queue data-structure. The priority queue consists of an array +.Va qs[NQS] +of queue header structures each of which identifies a list of runnable +processes of equal priority +.Pq see Fa <sys/proc.h> . +A single word +.Va whichqs +containing a bit mask identifying non-empty queues assists in selecting +a process quickly. +.Fn cpu_switch +must remove the first process from the list on the queue +with the highest priority +.Po lower indices in Va sq +indicate higher priority +.Pc , +and assign the address of its process structure to the global variable +.Dv curproc . +If no processes are available on the run queues, +.Fn cpu_switch +shall go into an +.Dq idle +loop. The idle loop must allow interrupts to be taken that will eventually +cause processes to appear again on the run queues. The variable +.Va curproc +should be +.Dv NULL +while +.Fn cpu_switch +waits for this to happen. +.Pp +Note that +.Fn mi_switch +and thus +.Fn cpu_switch +should be called at splhigh(). +.Pp +.Sh SEE ALSO +.Xr issignal 9 , +.Xr spl 9 , +.Xr tsleep 9 , +.Xr wakeup 9 +.Pp |
