Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

DELETE_MODULE

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

NAME

delete_module − unload a kernel module

SYNOPSIS

int delete_module(const char *name, int flags);

Note: No declaration of this function is provided in glibc headers; see NOTES.

DESCRIPTION

The delete_module() system call attempts to remove the unused loadable module entry identified by name. If the module has an exit function, then that function is executed before unloading the module. The 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:

	1.		If there are other loaded modules that depend on (i.e., refer to symbols defined in) this module, then the call fails.
	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.
	3.		If a module has a nonzero reference count, then the behavior depends on the bits set in flags. In normal usage (see NOTES), the O_NONBLOCK flag is always specified, and the O_TRUNC flag may additionally be specified.

The various combinations for flags have the following effect:
flags == O_NONBLOCK

The call returns immediately, with an error.

flags == (O_NONBLOCK | O_TRUNC)

The module is unloaded immediately, regardless of whether it has a nonzero reference count.

(flags & O_NONBLOCK) == 0

If flags does not specify O_NONBLOCK, the following steps occur:

	*		The module is marked so that no new references are permitted.
	*		If the module’s reference count is nonzero, the caller is placed in an uninterruptible sleep state (TASK_UNINTERRUPTIBLE) until the reference count is zero, at which point the call unblocks.
	*		The module is unloaded in the usual way.

The O_TRUNC flag has one further effect on the rules described above. By default, if a module has an init function but no exit function, then an attempt to remove the module will fail. However, if O_TRUNC was specified, this requirement is bypassed.

Using the O_TRUNC flag is dangerous! If the kernel was not built with CONFIG_MODULE_FORCE_UNLOAD, this flag is silently ignored. (Normally, CONFIG_MODULE_FORCE_UNLOAD is enabled.) Using this flag taints the kernel (TAINT_FORCED_RMMOD).

RETURN VALUE

On success, zero is returned. On error, −1 is returned and errno is set appropriately.

ERRORS

	EBUSY		The module is not "live" (i.e., it is still being initialized or is already marked for removal); or, the module has an init function but has no exit function, and O_TRUNC was not specified in flags.
	EFAULT		name refers to a location outside the process’s accessible address space.
	ENOENT		No module by that name exists.
	EPERM		The caller was not privileged (did not have the CAP_SYS_MODULE capability), or module unloading is disabled (see /proc/sys/kernel/modules_disabled in proc(5)).

EWOULDBLOCK

Other modules depend on this module; or, O_NONBLOCK was specified in flags, but the reference count of this module is nonzero and O_TRUNC was not specified in flags.

CONFORMING TO

delete_module() is Linux-specific.

NOTES

The 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 syscall(2).

The uninterruptible sleep that may occur if O_NONBLOCK is omitted from flags is considered undesirable, because the sleeping process is left in an unkillable state. As at Linux 3.7, specifying O_NONBLOCK is optional, but in future kernels it is likely to become mandatory.

Linux 2.4 and earlier
In Linux 2.4 and earlier, the system call took only one argument:

int delete_module(const char *name);

If name is NULL, all unused modules marked auto-clean are removed.

Some further details of differences in the behavior of delete_module() in Linux 2.4 and earlier are not currently explained in this manual page.

COLOPHON

This page is part of release 3.69 of the Linux 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/.

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.