delete_module - unload a kernel module
int delete_module(const char *name, int flags);
: No declaration of this system call is provided in glibc headers;
() 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
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:
- If there are other loaded modules that depend on (i.e., refer to symbols
defined in) this module, then the call fails.
- Otherwise, if the reference count for the module (i.e., the number of
processes currently using the module) is zero, then the module is
- 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
- (flags & O_NONBLOCK) == 0
- If flags does not specify O_NONBLOCK, the following steps
- 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.
flag has one further effect on the rules described above. By
default, if a module has an init
function but no exit
then an attempt to remove the module fails. However, if O_TRUNC
specified, this requirement is bypassed.
Using the O_TRUNC
flag is dangerous! If the kernel was not built with
, this flag is silently ignored. (Normally,
is enabled.) Using this flag taints the
On success, zero is returned. On error, -1 is returned and errno
- 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
- name refers to a location outside the process's accessible address
- No module by that name exists.
- 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)).
- 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.
() is Linux-specific.
() 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 syscall
The uninterruptible sleep that may occur if O_NONBLOCK
is omitted from
is considered undesirable, because the sleeping process is left
in an unkillable state. As at Linux 3.7, specifying O_NONBLOCK
optional, but in future kernels it is likely to become mandatory.
In Linux 2.4 and earlier, the system call took only one argument:
int delete_module(const char *name);
is NULL, all unused modules marked auto-clean are removed.
Some further details of differences in the behavior of delete_module
Linux 2.4 and earlier are not
currently explained in this manual page.