DELETE_MODULE(2)	   Linux Programmer's Manual	      DELETE_MODULE(2)



NAME
       delete_module - unload a kernel module

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

       Note:  No declaration of this system call 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 addi-
	   tionally 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  per-
		     mitted.

		  *  If the module's reference count is nonzero, the caller is
		     placed in an uninterruptible sleep	 state	(TASK_UNINTER-
		     RUPTIBLE)	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 func-
	      tion  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/ker-
	      nel/modules_disabled in proc(5)).

       EWOULDBLOCK
	      Other  modules  depend on this module; or, O_NONBLOCK was speci-
	      fied 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 declara-
       tion 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; alter-
       natively, 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.

SEE ALSO
       create_module(2),   init_module(2),   query_module(2),  lsmod(8),  mod-
       probe(8), rmmod(8)

COLOPHON
       This page is part of release 4.10 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
       https://www.kernel.org/doc/man-pages/.



Linux				  2016-03-15		      DELETE_MODULE(2)