delete_module man page on ElementaryOS

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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: There is no glibc wrapper for this system call; 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
       Glibc does not provide a wrapper for this system call;  call  it	 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 3.54 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux				  2012-11-08		      DELETE_MODULE(2)
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