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diff --git a/static/netbsd/man9/ltsleep.9 b/static/netbsd/man9/ltsleep.9 new file mode 100644 index 00000000..0c727004 --- /dev/null +++ b/static/netbsd/man9/ltsleep.9 @@ -0,0 +1,284 @@ +.\" $NetBSD: ltsleep.9,v 1.20 2024/05/07 15:40:15 christos Exp $ +.\" +.\" Copyright (c) 1996, 2002, 2007 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. +.\" +.\" 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 May 7, 2024 +.Dt LTSLEEP 9 +.Os +.Sh NAME +.Nm ltsleep , +.Nm mtsleep , +.Nm tsleep , +.Nm wakeup +.Nd process context sleep and wakeup +.Sh SYNOPSIS +.In sys/proc.h +.Ft int +.Fn "mtsleep" "wchan_t ident" "pri_t priority" "const char *wmesg" "int timo" "kmutex_t *mtx" +.Ft int +.Fn "tsleep" "wchan_t ident" "pri_t priority" "const char *wmesg" "int timo" +.Ft void +.Fn "wakeup" "wchan_t ident" +.Sh DESCRIPTION +.Em The interfaces described in this manual page are obsolete +.Em and will be removed from a future version of the system. +.Pp +.Em The +.Em Fn ltsleep +.Em interface has been obsoleted and removed from the system. +.Pp +.Em Please see the +.Xr condvar 9 , +.Xr mutex 9 , +.Em and +.Xr rwlock 9 +.Em manual pages for information on kernel synchronisation primitives. +.Pp +These functions implement voluntary context switching. +.Fn tsleep +and +.Fn mtsleep +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. +.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 \(em after it has acquired a +context again \(em retry the action that blocked its operation to see +if the +.Dq blocking +condition has cleared. +.Pp +The +.Fn tsleep +and +.Fn mtsleep +functions take 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 mtsleep +function takes an additional argument and flag: +.Bl -tag -width priority +.It Fa mtx +A +.Xr mutex 9 +representing the lock protecting the data-structures. +On entry +.Fn mtsleep +will release the lock and re-acquire the lock on return. +.It Fa priority +If the flag +.Dv PNORELOCK +is OR'ed into +.Fa priority +then +.Fn mtsleep +will not re-acquire the lock. +.El +.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 tsleep +or +.Fn mtsleep . +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. +.Sh RETURN VALUES +.Fn tsleep +and +.Fn mtsleep +return 0 if they return as a result of a +.Fn wakeup . +If a +.Fn tsleep +and +.Fn mtsleep +return 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 +and +.Fn mtsleep +return because of a timeout, the return value is +.Er EWOULDBLOCK . +.Sh MIGRATING TO CONDVAR +Note the conversion from tsleep/wakeup into +.Xr condvar 9 +should not be done mechanically i.e. +.Dq blindly . +Code logic should be understood before changing, and it may also need to be +revisited for the change. +Please also read the +.Xr condvar 9 +man page. +.Pp +The +.Fn tsleep +and +.Fn mtsleep , +and +.Fn wakeup +pairs should generally be replaced by +.Xr cv_wait 9 / +.Xr cv_wait_sig 9 / +.Xr cv_timedwait 9 / +.Xr cv_timedwait_sig 9 +and +.Xr cv_signal 9 / +.Xr cv_broadcast 9 +pairs. +The +.Fn cv_wait* +variant to use can be determined from looking at the corresponding +.Fn tsleep +usage. +.Pp +There are two arguments of interest: +.Ar timo +and +.Ar priority . +The +.Ar priority +value may have OR'ed the flag +.Dv PCATCH . +.Pp +The +.Dv PCATCH +flag means that the blocking thread should be awoken on signal, and +the sleep call should be replaced with +.Xr cv_wait_sig 9 . +.Pp +The +.Ar timo +value, if it is not zero, indicates how long to sleep, and +the sleep call should be replaced with +.Xr cv_timedwait 9 . +.Pp +If both the +.Dv PCATCH +flag and a non-zero +.Ar timo +value are specified, then +.Xr cv_timedwait_sig 9 +should be used. +.Pp +A +.Xr mutex 9 +(interlock) must be held across +.Fn cv_wait +and +.Fn cv_broadcast +calls, in order to protect state. +Most old code will require the addition of locking, whereas some will +require amending to remove +.Dv PNORELOCK . +.Sh SEE ALSO +.Xr sigaction 2 , +.Xr condvar 9 , +.Xr hz 9 , +.Xr kpause 9 , +.Xr mutex 9 , +.Xr rwlock 9 +.Sh HISTORY +The sleep/wakeup process synchronization mechanism is very old. +It appeared in a very early version of Unix. +.Fn tsleep +appeared in +.Bx 4.4 . +.Fn ltsleep +appeared in +.Nx 1.5 . |