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-.TH DELETE_MODULE 2 2014-05-10 "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
-
-.IR Note :
-No declaration of this function is provided in glibc headers; see NOTES.
-.SH DESCRIPTION
-The
-.BR delete_module ()
-system call attempts to remove the unused loadable module entry
-identified by
-.IR name .
-If the module has an
-.I exit
-function, then that function is executed before unloading the module.
-The
-.IR flags
-argument is used to modify the behavior of the system call,
-as described below.
-This system call requires privilege.
-
-Module removal is attempted according to the following rules:
-.IP 1. 4
-If there are other loaded modules that depend on
-(i.e., refer to symbols defined in) this module,
-then the call fails.
-.IP 2.
-Otherwise, if the reference count for 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,
-then the behavior depends on the bits set in
-.IR flags .
-In normal usage (see NOTES), the
-.BR O_NONBLOCK
-flag is always specified, and the
-.BR O_TRUNC
-flag may additionally be specified.
-.\" O_TRUNC == KMOD_REMOVE_FORCE in kmod library
-.\" O_NONBLOCK == KMOD_REMOVE_NOWAIT in kmod library
-
-The various combinations for
-.I flags
-have the following effect:
-.RS 4
-.TP
-.B flags == O_NONBLOCK
-The call returns immediately, with an error.
-.TP
-.B flags == (O_NONBLOCK | O_TRUNC)
-The module is unloaded immediately,
-regardless of whether it has a nonzero reference count.
-.TP
-.B (flags & O_NONBLOCK) == 0
-If
-.I flags
-does not specify
-.BR O_NONBLOCK ,
-the following steps occur:
-.RS
-.IP * 3
-The module is marked so that no new references are permitted.
-.IP *
-If the module's reference count is nonzero,
-the caller is placed in an uninterruptible sleep state
-.RB ( TASK_UNINTERRUPTIBLE )
-until the reference count is zero, at which point the call unblocks.
-.IP *
-The module is unloaded in the usual way.
-.RE
-.RE
-.PP
-The
-.B O_TRUNC
-flag has one further effect on the rules described above.
-By default, if a module has an
-.I init
-function but no
-.I exit
-function, then an attempt to remove the module will fail.
-However, if
-.BR O_TRUNC
-was specified, this requirement is bypassed.
-.PP
-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,
-.BR CONFIG_MODULE_FORCE_UNLOAD
-is enabled.)
-Using this flag taints the kernel (TAINT_FORCED_RMMOD).
-.SH RETURN VALUE
-On success, zero is returned.
-On error, \-1 is returned and
-.I errno
-is set appropriately.
-.SH ERRORS
-.TP
-.B EBUSY
-The module is not "live"
-(i.e., it is still being initialized or is already marked for removal);
-or, the module has
-an
-.I init
-function but has no
-.I exit
-function, and
-.B O_TRUNC
-was not specified in
-.IR flags .
-.TP
-.B EFAULT
-.I name
-refers to a location outside the process's accessible address space.
-.TP
-.B ENOENT
-No module by that name exists.
-.TP
-.B EPERM
-The caller was not privileged
-(did not have the
-.B CAP_SYS_MODULE
-capability),
-or module unloading is disabled
-(see
-.IR /proc/sys/kernel/modules_disabled
-in
-.BR proc (5)).
-.TP
-.B EWOULDBLOCK
-Other modules depend on this module;
-or,
-.BR O_NONBLOCK
-was specified in
-.IR flags ,
-but the reference count of this module is nonzero and
-.B O_TRUNC
-was not specified in
-.IR flags .
-.SH CONFORMING TO
-.BR delete_module ()
-is Linux-specific.
-.SH NOTES
-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 does export an ABI for this system call.
-Therefore, in order to employ this system call,
-it is sufficient to manually declare the interface in your code;
-alternatively, you can invoke the system call using
-.BR syscall (2).
-
-The uninterruptible sleep that may occur if
-.BR O_NONBLOCK
-is omitted from
-.IR flags
-is considered undesirable, because the sleeping process is left
-in an unkillable state.
-As at Linux 3.7, specifying
-.BR O_NONBLOCK
-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:
-
-.BI " int delete_module(const char *" name );
-
-If
-.I name
-is NULL, all unused modules marked auto-clean are removed.
-
-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
-.BR create_module (2),
-.BR init_module (2),
-.BR query_module (2),
-.BR lsmod (8),
-.BR modprobe (8),
-.BR rmmod (8)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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