.\" Copyright (C) 2012 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
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-.TH DELETE_MODULE 2 2012-10-24 "Linux" "Linux Programmer's Manual"
+.TH DELETE_MODULE 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
delete_module \- unload a kernel module
.SH SYNOPSIS
.nf
.BI "int delete_module(const char *" name ", int " flags );
.fi
-
+.PP
.IR Note :
-There is no glibc wrapper for this system call; see NOTES.
+No declaration of this system call is provided in glibc headers; see NOTES.
.SH DESCRIPTION
The
.BR delete_module ()
argument is used to modify the behavior of the system call,
as described below.
This system call requires privilege.
-
+.PP
Module removal is attempted according to the following rules:
.IP 1. 4
If there are other loaded modules that depend on
then the call fails.
.IP 2.
Otherwise, if the reference count for the module
-(i.e., the number of processes currently using the module)
+(i.e., the number of processes currently using the module)
is zero, then the module is immediately unloaded.
.IP 3.
If a module has a nonzero reference count,
flag may additionally be specified.
.\" O_TRUNC == KMOD_REMOVE_FORCE in kmod library
.\" O_NONBLOCK == KMOD_REMOVE_NOWAIT in kmod library
-
+.IP
The various combinations for
.I flags
have the following effect:
The
.B O_TRUNC
flag has one further effect on the rules described above.
-By default,
-attempting to remove a module that has an
+By default, if a module has an
.I init
function but no
-.I exit
-function fails.
+.I exit
+function, then an attempt to remove the module fails.
However, if
.BR O_TRUNC
was specified, this requirement is bypassed.
.PP
-Using the
+Using the
.B O_TRUNC
flag is dangerous!
If the kernel was not built with
.BR CONFIG_MODULE_FORCE_UNLOAD ,
this flag is silently ignored.
-(Normally ,
+(Normally,
.BR CONFIG_MODULE_FORCE_UNLOAD
is enabled.)
Using this flag taints the kernel (TAINT_FORCED_RMMOD).
-.SH "RETURN VALUE"
+.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned and
.I errno
.B O_TRUNC
was not specified in
.IR flags .
-
.TP
.B EFAULT
.I name
.BR O_NONBLOCK
was specified in
.IR flags ,
-but the reference count of this module is nonzero and
+but the reference count of this module is nonzero and
.B O_TRUNC
was not specified in
.IR flags .
-.SH "CONFORMING TO"
+.SH CONFORMING TO
.BR delete_module ()
is Linux-specific.
.SH NOTES
-Glibc does not provide a wrapper for this system call; call it using
+The
+.BR delete_module ()
+system call is not supported by glibc.
+No declaration is provided in glibc headers, but, through a quirk of history,
+glibc versions before 2.23 did export an ABI for this system call.
+Therefore, in order to employ this system call,
+it is (before glibc 2.23) sufficient to
+manually declare the interface in your code;
+alternatively, you can invoke the system call using
.BR syscall (2).
-
+.PP
The uninterruptible sleep that may occur if
.BR O_NONBLOCK
is omitted from
is optional, but in future kernels it is likely to become mandatory.
.SS Linux 2.4 and earlier
In Linux 2.4 and earlier, the system call took only one argument:
-
+.PP
.BI " int delete_module(const char *" name );
-
+.PP
If
.I name
is NULL, all unused modules marked auto-clean are removed.
-
+.PP
Some further details of differences in the behavior of
.BR delete_module ()
in Linux 2.4 and earlier are
.I not
currently explained in this manual page.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR create_module (2),
.BR init_module (2),
.BR query_module (2),