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diff --git a/share/man/man9/sleep.9 b/share/man/man9/sleep.9 new file mode 100644 index 00000000000..a30bb43c95a --- /dev/null +++ b/share/man/man9/sleep.9 @@ -0,0 +1,183 @@ +.\" $NetBSD: sleep.9,v 1.11 1999/03/24 06:15:12 mycroft 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 FOUNDATION 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 June 23, 1996 +.Dt SLEEP 9 +.Os +.Sh NAME +.Nm sleep , +.Nm tsleep , +.Nm wakeup +.Nd process context sleep and wakeup +.Sh SYNOPSIS +.Fd #include <sys/types.h> +.Fd #include <sys/proc.h> +.Ft int +.Fn "tsleep" "void *ident" "int priority" "const char *wmesg" "int timo" +.Ft void +.Fn "sleep" "void *ident" "int priority" +.Ft void +.Fn "wakeup" "void *ident" +.Sh DESCRIPTION +These functions implement voluntary context switching. +.Fn tsleep +and +.Fn sleep +are used throughout the kernel whenever processing in the current context +can not continue for any of the following reasons: +.Bl -bullet -offset indent +.It +The current process needs to await the results of a pending I/O operation. +.It +The current process needs resources +.Pq e.g. memory +which are temporarily unavailable. +.It +The current process wants access to data structures which are locked by +other processes. +.El +.Pp +The function +.Fn wakeup +is used to notify sleeping processes of possible changes to the condition +that caused them to go to sleep. +Typically, an awakened process will -- after it has acquired a context +again -- retry the action that blocked its operation to see if the +.Dq blocking +condition has cleared. +.Pp +The +.Va bpendsleep +label can be used as a break-point to debug a process coming back from +.Fn tsleep . +.Pp +The +.Fn tsleep +function takes the following arguments: +.Bl -tag -width priority +.It Fa ident +An identifier of the +.Dq wait channel +representing the resource for which the current process needs to wait. +This typically is the virtual address of some kernel data structure related +to the resource for which the process is contending. +The same identifier must be used in a call to +.Fn wakeup +to get the process going again. +.Fa ident +should not be +.Dv NULL . +.It Fa priority +The process priority to be used when the process is awakened and put on +the queue of runnable processes. +This mechanism is used to optimize +.Dq throughput +of processes executing in kernel mode. +If the flag +.Dv PCATCH +is OR'ed into +.Fa priority +the process checks for posted signals before and after sleeping. +.It Fa wmesg +A pointer to a character string indicating the reason a process is sleeping. +The kernel does not use the string, but makes it available +.Pq through the process structure field Li p_wmesg +for user level utilities such as +.Xr ps 1 . +.It Fa timo +If non-zero, the process will sleep for at most +.Li timo/hz +seconds. +If this amount of time elapses and no +.Fn wakeup "ident" +has occurred, and no signal +.Pq if Dv PCATCH No was set +was posted, +.Fn tsleep +will return +.Er EWOULDBLOCK . +.El +.Pp +The +.Fn sleep +function puts the process in an uninterruptible sleep. +It is functionally equivalent to: +.Bd -literal -offset indent +tsleep(ident, priority & PRIMASK, 0, 0) +.Ed +.Pp +The +.Fn wakeup +function will mark all processes which are currently sleeping on the identifier +.Fa ident +as runnable. +Eventually, each of the processes will resume execution in the kernel +context, causing a return from +.Fn [t]sleep . +Note that processes returning from sleep should always re-evaluate the +conditions that blocked them, since a call to +.Fn wakeup +merely signals a +.Em possible +change to the blocking conditions. +For example, when two or more processes are waiting for an exclusive lock, +only one of them will succeed in acquiring the lock when it is released. +All others will have to go back to sleep and wait for the next opportunity. +.Sh RETURN VALUES +.Fn tsleep +returns 0 if it returns as a result of a +.Fn wakeup . +If a +.Fn tsleep +returns as a result of a signal, the return value is +.Er ERESTART +if the signal has the +.Dv SA_RESTART +property +.Pq see Xr sigaction 2 , +and +.Er EINTR +otherwise. +If +.Fn tsleep +returns as a result of a timeout, the return value is +.Er EWOULDBLOCK . +.Sh CODE REFERENCES +These functions are implemented in the file +.Pa sys/kern/kern_synch.c . +.Sh SEE ALSO +.Xr hz 9 , +.Xr timeout 9 |