kgess-mirror/freebsd-src
1
0
Fork 0
mirror of https://git.freebsd.org/src.git synced 2026-01-12 06:54:03 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

kqueue.2: document KQUEUE_CPONFORK

Browse source 
Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D52045
This commit is contained in:
Konstantin Belousov 2025-10-08 06:06:20 +03:00
parent 3613896984
commit a4981edede
1 changed files with 28 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

29
lib/libsys/kqueue.2
View file

@ -97,10 +97,37 @@ 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"
.Bl -tag -width "KQUEUE_CPONFORK"
.It Dv KQUEUE_CLOEXEC
The returned file descriptor is automatically closed on
.Xr execve 2
.It Dv KQUEUE_CPONFORK
When this flag is set, the created kqueue is copied into
the child process on
.Xr fork 2
calls.
The kqueue descriptor index of the new kqueue will be inherited by the child,
that is, the numeric value of the descriptor will remain the same.
.Pp
Copying is deep, that is, each registered event in the original kqueue is
copied (and not shared) into the new kqueue.
This is contrary to how other descriptor types are handled upon
.Xr fork 2 ,
where the copied file descriptor references the same file object
as the source descriptor (shallow copy).
.Pp
By default, in other words, when the flag is not set, kqueues from
the parent are not copied on fork to the child process.
The corresponding file descriptor indeces are unused in the child.
.Pp
Registered events that reference file descriptors which are not
duplicated on fork, are not copied into the new kqueue.
For instance, if the event references a file descriptor opened with the
.Dv O_CLOEXEC
flag set, it is not copied.
Similarly, if event references a kqueue opened without the
.Dv KQUEUE_CPONFORK
flag, the event is not copied.
.El
.Pp
The