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
           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

       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), modprobe(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)