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diff --git a/lib/libsys/kqueue.2 b/lib/libsys/kqueue.2 new file mode 100644 index 000000000000..d6e949baa24c --- /dev/null +++ b/lib/libsys/kqueue.2 @@ -0,0 +1,904 @@ +.\" Copyright (c) 2000 Jonathan Lemon +.\" All rights reserved. +.\" +.\" 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 ``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 AUTHOR 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 March 26, 2023 +.Dt KQUEUE 2 +.Os +.Sh NAME +.Nm kqueue , +.Nm kevent +.Nd kernel event notification mechanism +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/event.h +.Ft int +.Fn kqueue "void" +.Ft int +.Fn kqueuex "u_int flags" +.Ft int +.Fn kqueue1 "int flags" +.Ft int +.Fo kevent +.Fa "int kq" +.Fa "const struct kevent *changelist" +.Fa "int nchanges" +.Fa "struct kevent *eventlist" +.Fa "int nevents" +.Fa "const struct timespec *timeout" +.Fc +.Fn EV_SET "kev" ident filter flags fflags data udata +.Sh DESCRIPTION +The +.Fn kqueue +system call +provides a generic method of notifying the user when an event +happens or a condition holds, based on the results of small +pieces of kernel code termed filters. +A kevent is identified by the (ident, filter) pair; there may only +be one unique kevent per kqueue. +.Pp +The filter is executed upon the initial registration of a kevent +in order to detect whether a preexisting condition is present, and is also +executed whenever an event is passed to the filter for evaluation. +If the filter determines that the condition should be reported, +then the kevent is placed on the kqueue for the user to retrieve. +.Pp +The filter is also run when the user attempts to retrieve the kevent +from the kqueue. +If the filter indicates that the condition that triggered +the event no longer holds, the kevent is removed from the kqueue and +is not returned. +.Pp +Multiple events which trigger the filter do not result in multiple +kevents being placed on the kqueue; instead, the filter will aggregate +the events into a single struct kevent. +Calling +.Fn close +on a file descriptor will remove any kevents that reference the descriptor. +.Pp +The +.Fn kqueue +system call +creates a new kernel event queue and returns a descriptor. +The queue is not inherited by a child created with +.Xr fork 2 . +However, if +.Xr rfork 2 +is called without the +.Dv RFFDG +flag, then the descriptor table is shared, +which will allow sharing of the kqueue between two processes. +.Pp +The +.Fn kqueuex +system call also creates a new kernel event queue, and additionally takes +a +.Fa flags +argument, which is a bitwise-inclusive OR of the following flags: +.Bl -tag -width "KQUEUE_CLOEXEC" +.It Dv KQUEUE_CLOEXEC +The returned file descriptor is automatically closed on +.Xr execve 2 +.El +.Pp +The +.Fn kqueue +system call is equivalent to calling +.Fn kqueuex +with +.Fa flags +set to 0. +.Pp +The +.Fn kqueue1 +function exists for compatibility with +.Nx . +The +.Fa flags +argument accepts zero or more of the following values: +.Bl -tag -width O_CLOEXEC +.It Dv O_CLOEXEC +The returned file descriptor is automatically closed on +.Xr execve 2 +.El +.Pp +The +.Fn kevent +system call +is used to register events with the queue, and return any pending +events to the user. +The +.Fa changelist +argument +is a pointer to an array of +.Va kevent +structures, as defined in +.In sys/event.h . +All changes contained in the +.Fa changelist +are applied before any pending events are read from the queue. +The +.Fa nchanges +argument +gives the size of +.Fa changelist . +The +.Fa eventlist +argument +is a pointer to an array of kevent structures. +The +.Fa nevents +argument +determines the size of +.Fa eventlist . +When +.Fa nevents +is zero, +.Fn kevent +will return immediately even if there is a +.Fa timeout +specified unlike +.Xr select 2 . +If +.Fa timeout +is a non-NULL pointer, it specifies a maximum interval to wait +for an event, which will be interpreted as a struct timespec. +If +.Fa timeout +is a NULL pointer, +.Fn kevent +waits indefinitely. +To effect a poll, the +.Fa timeout +argument should be non-NULL, pointing to a zero-valued +.Va timespec +structure. +The same array may be used for the +.Fa changelist +and +.Fa eventlist . +.Pp +The +.Fn EV_SET +macro is provided for ease of initializing a +kevent structure. +.Pp +The +.Va kevent +structure is defined as: +.Bd -literal +struct kevent { + uintptr_t ident; /* identifier for this event */ + short filter; /* filter for event */ + u_short flags; /* action flags for kqueue */ + u_int fflags; /* filter flag value */ + int64_t data; /* filter data value */ + void *udata; /* opaque user data identifier */ + uint64_t ext[4]; /* extensions */ +}; +.Ed +.Pp +The fields of +.Fa struct kevent +are: +.Bl -tag -width "Fa filter" +.It Fa ident +Value used to identify this event. +The exact interpretation is determined by the attached filter, +but often is a file descriptor. +.It Fa filter +Identifies the kernel filter used to process this event. +The pre-defined +system filters are described below. +.It Fa flags +Actions to perform on the event. +.It Fa fflags +Filter-specific flags. +.It Fa data +Filter-specific data value. +.It Fa udata +Opaque user-defined value passed through the kernel unchanged. +.It Fa ext +Extended data passed to and from kernel. +The meaning of the +.Fa ext[0] +and +.Fa ext[1] +members is defined by the filter. +If a filter does not use them, +these members are passed through the kernel unchanged. +The +.Fa ext[2] +and +.Fa ext[3] +members are always passed through the kernel unchanged, +providing additional user-defined values. +.El +.Pp +The +.Va flags +field can contain the following values: +.Bl -tag -width EV_KEEPUDATA +.It Dv EV_ADD +Adds the event to the kqueue. +Re-adding an existing event +will modify the parameters of the original event, and not result +in a duplicate entry. +Adding an event automatically enables it, +unless overridden by the EV_DISABLE flag. +.It Dv EV_ENABLE +Permit +.Fn kevent +to return the event if it is triggered. +.It Dv EV_DISABLE +Disable the event so +.Fn kevent +will not return it. +The filter itself is not disabled. +.It Dv EV_DISPATCH +Disable the event source immediately after delivery of an event. +See +.Dv EV_DISABLE +above. +.It Dv EV_DELETE +Removes the event from the kqueue. +Events which are attached to +file descriptors are automatically deleted on the last close of +the descriptor. +.It Dv EV_RECEIPT +This flag is useful for making bulk changes to a kqueue without draining +any pending events. +When passed as input, it forces +.Dv EV_ERROR +to always be returned. +When a filter is successfully added the +.Va data +field will be zero. +Note that if this flag is encountered and there is no remaining space in +.Fa eventlist +to hold the +.Dv EV_ERROR +event, then subsequent changes will not get processed. +.It Dv EV_ONESHOT +Return only the first occurrence of the filter +being triggered. +After the user retrieves the event from the kqueue, +it is deleted. +.It Dv EV_CLEAR +Reset the state of the event after it is retrieved by the user. +This is useful for filters which report state transitions +instead of the current state. +Note that some filters may automatically +set this flag internally. +.It Dv EV_EOF +Filters may set this flag to indicate filter-specific EOF condition. +.It Dv EV_ERROR +See +.Sx RETURN VALUES +below. +.It Dv EV_KEEPUDATA +Preserve the +.Fa udata +associated with an existing event. +This allows other aspects of the event to be modified without requiring the +caller to know the +.Fa udata +value previously registered with the event. +This is especially useful with +.Dv NOTE_TRIGGER +or +.Dv EV_ENABLE . +This flag may not be used with +.Dv EV_ADD . +.El +.Pp +The predefined system filters are listed below. +Arguments may be passed to and from the filter via the +.Va fflags +and +.Va data +fields in the kevent structure. +.Bl -tag -width "Dv EVFILT_PROCDESC" +.It Dv EVFILT_READ +Takes a descriptor as the identifier, and returns whenever +there is data available to read. +The behavior of the filter is slightly different depending +on the descriptor type. +.Bl -tag -width 2n +.It Sockets +Sockets which have previously been passed to +.Xr listen 2 +return when there is an incoming connection pending. +.Va data +contains the size of the listen backlog. +.Pp +Other socket descriptors return when there is data to be read, +subject to the +.Dv SO_RCVLOWAT +value of the socket buffer. +This may be overridden with a per-filter low water mark at the +time the filter is added by setting the +.Dv NOTE_LOWAT +flag in +.Va fflags , +and specifying the new low water mark in +.Va data . +On return, +.Va data +contains the number of bytes of protocol data available to read. +.Pp +If the read direction of the socket has shutdown, then the filter +also sets +.Dv EV_EOF +in +.Va flags , +and returns the socket error (if any) in +.Va fflags . +It is possible for EOF to be returned (indicating the connection is gone) +while there is still data pending in the socket buffer. +.It Vnodes +Returns when the file pointer is not at the end of file. +.Va data +contains the offset from current position to end of file, +and may be negative. +.Pp +This behavior is different from +.Xr poll 2 , +where read events are triggered for regular files unconditionally. +This event can be triggered unconditionally by setting the +.Dv NOTE_FILE_POLL +flag in +.Va fflags . +.It "Fifos, Pipes" +Returns when the there is data to read; +.Va data +contains the number of bytes available. +.Pp +When the last writer disconnects, the filter will set +.Dv EV_EOF +in +.Va flags . +This will be cleared by the filter when a new writer connects, +at which point the +filter will resume waiting for data to become available before +returning. +.It "BPF devices" +Returns when the BPF buffer is full, the BPF timeout has expired, or +when the BPF has +.Dq immediate mode +enabled and there is any data to read; +.Va data +contains the number of bytes available. +.It Eventfds +Returns when the counter is greater than 0; +.Va data +contains the counter value, which must be cast to +.Vt uint64_t . +.It Kqueues +Returns when pending events are present on the queue; +.Va data +contains the number of events available. +.El +.It Dv EVFILT_WRITE +Takes a descriptor as the identifier, and returns whenever +it is possible to write to the descriptor. +For sockets, pipes +and fifos, +.Va data +will contain the amount of space remaining in the write buffer. +The filter will set +.Dv EV_EOF +when the reader disconnects, and for the fifo case, this will be cleared +when a new reader connects. +Note that this filter is not supported for vnodes. +.Pp +For sockets, the low water mark and socket error handling is +identical to the +.Dv EVFILT_READ +case. +.Pp +For eventfds, +.Va data +will contain the maximum value that can be added to the counter +without blocking. +.Pp +For BPF devices, when the descriptor is attached to an interface the filter +always indicates that it is possible to write and +.Va data +will contain the MTU size of the underlying interface. +.It Dv EVFILT_EMPTY +Takes a descriptor as the identifier, and returns whenever +there is no remaining data in the write buffer. +.It Dv EVFILT_AIO +Events for this filter are not registered with +.Fn kevent +directly but are registered via the +.Va aio_sigevent +member of an asynchronous I/O request when it is scheduled via an +asynchronous I/O system call such as +.Fn aio_read . +The filter returns under the same conditions as +.Fn aio_error . +For more details on this filter see +.Xr sigevent 3 and +.Xr aio 4 . +.It Dv EVFILT_VNODE +Takes a file descriptor as the identifier and the events to watch for in +.Va fflags , +and returns when one or more of the requested events occurs on the descriptor. +The events to monitor are: +.Bl -tag -width "Dv NOTE_CLOSE_WRITE" +.It Dv NOTE_ATTRIB +The file referenced by the descriptor had its attributes changed. +.It Dv NOTE_CLOSE +A file descriptor referencing the monitored file, was closed. +The closed file descriptor did not have write access. +.It Dv NOTE_CLOSE_WRITE +A file descriptor referencing the monitored file, was closed. +The closed file descriptor had write access. +.Pp +This note, as well as +.Dv NOTE_CLOSE , +are not activated when files are closed forcibly by +.Xr unmount 2 or +.Xr revoke 2 . +Instead, +.Dv NOTE_REVOKE +is sent for such events. +.It Dv NOTE_DELETE +The +.Fn unlink +system call was called on the file referenced by the descriptor. +.It Dv NOTE_EXTEND +For regular file, the file referenced by the descriptor was extended. +.Pp +For directory, reports that a directory entry was added or removed, +as the result of rename operation. +The +.Dv NOTE_EXTEND +event is not reported when a name is changed inside the directory. +.It Dv NOTE_LINK +The link count on the file changed. +In particular, the +.Dv NOTE_LINK +event is reported if a subdirectory was created or deleted inside +the directory referenced by the descriptor. +.It Dv NOTE_OPEN +The file referenced by the descriptor was opened. +.It Dv NOTE_READ +A read occurred on the file referenced by the descriptor. +.It Dv NOTE_RENAME +The file referenced by the descriptor was renamed. +.It Dv NOTE_REVOKE +Access to the file was revoked via +.Xr revoke 2 +or the underlying file system was unmounted. +.It Dv NOTE_WRITE +A write occurred on the file referenced by the descriptor. +.El +.Pp +On return, +.Va fflags +contains the events which triggered the filter. +.It Dv EVFILT_PROC +Takes the process ID to monitor as the identifier and the events to watch for +in +.Va fflags , +and returns when the process performs one or more of the requested events. +If a process can normally see another process, it can attach an event to it. +The events to monitor are: +.Bl -tag -width "Dv NOTE_TRACKERR" +.It Dv NOTE_EXIT +The process has exited. +The exit status will be stored in +.Va data +in the same format as the status returned by +.Xr wait 2 . +.It Dv NOTE_FORK +The process has called +.Fn fork . +.It Dv NOTE_EXEC +The process has executed a new process via +.Xr execve 2 +or a similar call. +.It Dv NOTE_TRACK +Follow a process across +.Fn fork +calls. +The parent process registers a new kevent to monitor the child process +using the same +.Va fflags +as the original event. +The child process will signal an event with +.Dv NOTE_CHILD +set in +.Va fflags +and the parent PID in +.Va data . +.Pp +If the parent process fails to register a new kevent +.Pq usually due to resource limitations , +it will signal an event with +.Dv NOTE_TRACKERR +set in +.Va fflags , +and the child process will not signal a +.Dv NOTE_CHILD +event. +.El +.Pp +On return, +.Va fflags +contains the events which triggered the filter. +.It Dv EVFILT_PROCDESC +Takes the process descriptor created by +.Xr pdfork 2 +to monitor as the identifier and the events to watch for in +.Va fflags , +and returns when the associated process performs one or more of the +requested events. +The events to monitor are: +.Bl -tag -width "Dv NOTE_EXIT" +.It Dv NOTE_EXIT +The process has exited. +The exit status will be stored in +.Va data . +.El +.Pp +On return, +.Va fflags +contains the events which triggered the filter. +.It Dv EVFILT_SIGNAL +Takes the signal number to monitor as the identifier and returns +when the given signal is delivered to the process. +This coexists with the +.Fn signal +and +.Fn sigaction +facilities, and has a lower precedence. +The filter will record +all attempts to deliver a signal to a process, even if the signal has +been marked as +.Dv SIG_IGN , +except for the +.Dv SIGCHLD +signal, which, if ignored, will not be recorded by the filter. +Event notification happens after normal +signal delivery processing. +.Va data +returns the number of times the signal has occurred since the last call to +.Fn kevent . +This filter automatically sets the +.Dv EV_CLEAR +flag internally. +.It Dv EVFILT_TIMER +Establishes an arbitrary timer identified by +.Va ident . +When adding a timer, +.Va data +specifies the moment to fire the timer (for +.Dv NOTE_ABSTIME ) +or the timeout period. +The timer will be periodic unless +.Dv EV_ONESHOT +or +.Dv NOTE_ABSTIME +is specified. +On return, +.Va data +contains the number of times the timeout has expired since the last call to +.Fn kevent . +For non-monotonic timers, this filter automatically sets the +.Dv EV_CLEAR +flag internally. +.Pp +The filter accepts the following flags in the +.Va fflags +argument: +.Bl -tag -width "Dv NOTE_MSECONDS" +.It Dv NOTE_SECONDS +.Va data +is in seconds. +.It Dv NOTE_MSECONDS +.Va data +is in milliseconds. +.It Dv NOTE_USECONDS +.Va data +is in microseconds. +.It Dv NOTE_NSECONDS +.Va data +is in nanoseconds. +.It Dv NOTE_ABSTIME +The specified expiration time is absolute. +.El +.Pp +If +.Va fflags +is not set, the default is milliseconds. +On return, +.Va fflags +contains the events which triggered the filter. +.Pp +Periodic timers with a specified timeout of 0 will be silently adjusted to +timeout after 1 of the time units specified by the requested precision in +.Va fflags . +If an absolute time is specified that has already passed, then it is treated as +if the current time were specified and the event will fire as soon as possible. +.Pp +If an existing timer is re-added, the existing timer will be +effectively canceled (throwing away any undelivered record of previous +timer expiration) and re-started using the new parameters contained in +.Va data +and +.Va fflags . +.Pp +There is a system wide limit on the number of timers +which is controlled by the +.Va kern.kq_calloutmax +sysctl. +.It Dv EVFILT_USER +Establishes a user event identified by +.Va ident +which is not associated with any kernel mechanism but is triggered by +user level code. +The lower 24 bits of the +.Va fflags +may be used for user defined flags and manipulated using the following: +.Bl -tag -width "Dv NOTE_FFLAGSMASK" +.It Dv NOTE_FFNOP +Ignore the input +.Va fflags . +.It Dv NOTE_FFAND +Bitwise AND +.Va fflags . +.It Dv NOTE_FFOR +Bitwise OR +.Va fflags . +.It Dv NOTE_FFCOPY +Copy +.Va fflags . +.It Dv NOTE_FFCTRLMASK +Control mask for +.Va fflags . +.It Dv NOTE_FFLAGSMASK +User defined flag mask for +.Va fflags . +.El +.Pp +A user event is triggered for output with the following: +.Bl -tag -width "Dv NOTE_FFLAGSMASK" +.It Dv NOTE_TRIGGER +Cause the event to be triggered. +.El +.Pp +On return, +.Va fflags +contains the users defined flags in the lower 24 bits. +.El +.Sh CANCELLATION BEHAVIOUR +If +.Fa nevents +is non-zero, i.e., the function is potentially blocking, the call +is a cancellation point. +Otherwise, i.e., if +.Fa nevents +is zero, the call is not cancellable. +Cancellation can only occur before any changes are made to the kqueue, +or when the call was blocked and no changes to the queue were requested. +.Sh RETURN VALUES +The +.Fn kqueue +system call +creates a new kernel event queue and returns a file descriptor. +If there was an error creating the kernel event queue, a value of -1 is +returned and errno set. +.Pp +The +.Fn kevent +system call +returns the number of events placed in the +.Fa eventlist , +up to the value given by +.Fa nevents . +If an error occurs while processing an element of the +.Fa changelist +and there is enough room in the +.Fa eventlist , +then the event will be placed in the +.Fa eventlist +with +.Dv EV_ERROR +set in +.Va flags +and the system error in +.Va data . +Otherwise, +.Dv -1 +will be returned, and +.Dv errno +will be set to indicate the error condition. +If the time limit expires, then +.Fn kevent +returns 0. +.Sh EXAMPLES +.Bd -literal -compact +#include <sys/event.h> +#include <err.h> +#include <fcntl.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +int +main(int argc, char **argv) +{ + struct kevent event; /* Event we want to monitor */ + struct kevent tevent; /* Event triggered */ + int kq, fd, ret; + + if (argc != 2) + err(EXIT_FAILURE, "Usage: %s path\en", argv[0]); + fd = open(argv[1], O_RDONLY); + if (fd == -1) + err(EXIT_FAILURE, "Failed to open '%s'", argv[1]); + + /* Create kqueue. */ + kq = kqueue(); + if (kq == -1) + err(EXIT_FAILURE, "kqueue() failed"); + + /* Initialize kevent structure. */ + EV_SET(&event, fd, EVFILT_VNODE, EV_ADD | EV_CLEAR, NOTE_WRITE, + 0, NULL); + /* Attach event to the kqueue. */ + ret = kevent(kq, &event, 1, NULL, 0, NULL); + if (ret == -1) + err(EXIT_FAILURE, "kevent register"); + + for (;;) { + /* Sleep until something happens. */ + ret = kevent(kq, NULL, 0, &tevent, 1, NULL); + if (ret == -1) { + err(EXIT_FAILURE, "kevent wait"); + } else if (ret > 0) { + if (tevent.flags & EV_ERROR) + errx(EXIT_FAILURE, "Event error: %s", strerror(event.data)); + else + printf("Something was written in '%s'\en", argv[1]); + } + } + + /* kqueues are destroyed upon close() */ + (void)close(kq); + (void)close(fd); +} +.Ed +.Sh ERRORS +The +.Fn kqueue +system call fails if: +.Bl -tag -width Er +.It Bq Er ENOMEM +The kernel failed to allocate enough memory for the kernel queue. +.It Bq Er ENOMEM +The +.Dv RLIMIT_KQUEUES +rlimit +(see +.Xr getrlimit 2 ) +for the current user would be exceeded. +.It Bq Er EMFILE +The per-process descriptor table is full. +.It Bq Er ENFILE +The system file table is full. +.El +.Pp +The +.Fn kevent +system call fails if: +.Bl -tag -width Er +.It Bq Er EACCES +The process does not have permission to register a filter. +.It Bq Er EFAULT +There was an error reading or writing the +.Va kevent +structure. +.It Bq Er EBADF +The specified descriptor is invalid. +.It Bq Er EINTR +A signal was delivered before the timeout expired and before any +events were placed on the kqueue for return. +.It Bq Er EINTR +A cancellation request was delivered to the thread, but not yet handled. +.It Bq Er EINVAL +The specified time limit or filter is invalid. +.It Bq Er EINVAL +The specified length of the event or change lists is negative. +.It Bq Er ENOENT +The event could not be found to be modified or deleted. +.It Bq Er ENOMEM +No memory was available to register the event +or, in the special case of a timer, the maximum number of +timers has been exceeded. +This maximum is configurable via the +.Va kern.kq_calloutmax +sysctl. +.It Bq Er ESRCH +The specified process to attach to does not exist. +.El +.Pp +When +.Fn kevent +call fails with +.Er EINTR +error, all changes in the +.Fa changelist +have been applied. +.Sh SEE ALSO +.Xr aio_error 2 , +.Xr aio_read 2 , +.Xr aio_return 2 , +.Xr poll 2 , +.Xr read 2 , +.Xr select 2 , +.Xr sigaction 2 , +.Xr write 2 , +.Xr pthread_setcancelstate 3 , +.Xr signal 3 +.Rs +.%A Jonathan Lemon +.%T "Kqueue: A Generic and Scalable Event Notification Facility" +.%I USENIX Association +.%B Proceedings of the FREENIX Track: 2001 USENIX Annual Technical Conference +.%D June 25-30, 2001 +.\".http://www.usenix.org/event/usenix01/freenix01/full_papers/lemon/lemon.pdf +.Re +.Sh HISTORY +The +.Fn kqueue +and +.Fn kevent +system calls first appeared in +.Fx 4.1 . +The +.Fn kqueuex +system call +and +.Fn kevent1 +function first appeared in +.Fx 14.0 . +.Sh AUTHORS +The +.Fn kqueue +system and this manual page were written by +.An Jonathan Lemon Aq Mt jlemon@FreeBSD.org . +.Sh BUGS +.Pp +In versions older than +.Fx 12.0 , +.In sys/event.h +failed to parse without including +.In sys/types.h +manually. |