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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 3.65 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/.



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