DELETE_MODULE(2)          (2017-09-15)           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 mod-
          ule 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 speci-
              fied, and the O_TRUNC flag may additionally be speci-
              fied.

              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.

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                   *  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 func-
          tion but no exit function, then an attempt to remove the
          module fails.  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 ini-
               tialized 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 acces-
               sible 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 dis-
               abled (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

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          The delete_module() system call is not supported by glibc.
          No declaration 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; 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 5.10 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/.

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