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 function is provided in glibc headers; see NOTES.

DESCRIPTION
       The  delete_module() system call attempts to remove the unused loadable module entry iden‐
       tified 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 cur‐
           rently 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 ref‐
                  erence 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 unin‐
                     terruptible 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_MOD‐
       ULE_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 mod‐
              ule 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.

SEE ALSO
       create_module(2), init_module(2), query_module(2), lsmod(8), modprobe(8), rmmod(8)

COLOPHON
       This  page  is  part of release 3.74 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/.



Linux                                       2014-05-10                           DELETE_MODULE(2)