Documentation/feature-removal-schedule.txt

   1 The following is a list of files and features that are going to be
   2 removed in the kernel source tree.  Every entry should contain what
   3 exactly is going away, why it is happening, and who is going to be doing
   4 the work.  When the feature is removed from the kernel, it should also
   5 be removed from this file.
   6
   7 ---------------------------
   8
   9 What:   PRISM54
  10 When:   2.6.34
  11
  12 Why:    prism54 FullMAC PCI / Cardbus devices used to be supported only by the
  13         prism54 wireless driver. After Intersil stopped selling these
  14         devices in preference for the newer more flexible SoftMAC devices
  15         a SoftMAC device driver was required and prism54 did not support
  16         them. The p54pci driver now exists and has been present in the kernel for
  17         a while. This driver supports both SoftMAC devices and FullMAC devices.
  18         The main difference between these devices was the amount of memory which
  19         could be used for the firmware. The SoftMAC devices support a smaller
  20         amount of memory. Because of this the SoftMAC firmware fits into FullMAC
  21         devices's memory. p54pci supports not only PCI / Cardbus but also USB
  22         and SPI. Since p54pci supports all devices prism54 supports
  23         you will have a conflict. I'm not quite sure how distributions are
  24         handling this conflict right now. prism54 was kept around due to
  25         claims users may experience issues when using the SoftMAC driver.
  26         Time has passed users have not reported issues. If you use prism54
  27         and for whatever reason you cannot use p54pci please let us know!
  28         E-mail us at: linux-wireless@vger.kernel.org
  29
  30         For more information see the p54 wiki page:
  31
  32         http://wireless.kernel.org/en/users/Drivers/p54
  33
  34 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  35
  36 ---------------------------
  37
  38 What:   IRQF_SAMPLE_RANDOM
  39 Check:  IRQF_SAMPLE_RANDOM
  40 When:   July 2009
  41
  42 Why:    Many of IRQF_SAMPLE_RANDOM users are technically bogus as entropy
  43         sources in the kernel's current entropy model. To resolve this, every
  44         input point to the kernel's entropy pool needs to better document the
  45         type of entropy source it actually is. This will be replaced with
  46         additional add_*_randomness functions in drivers/char/random.c
  47
  48 Who:    Robin Getz <rgetz@blackfin.uclinux.org> & Matt Mackall <mpm@selenic.com>
  49
  50 ---------------------------
  51
  52 What:   Deprecated snapshot ioctls
  53 When:   2.6.36
  54
  55 Why:    The ioctls in kernel/power/user.c were marked as deprecated long time
  56         ago. Now they notify users about that so that they need to replace
  57         their userspace. After some more time, remove them completely.
  58
  59 Who:    Jiri Slaby <jirislaby@gmail.com>
  60
  61 ---------------------------
  62
  63 What:   The ieee80211_regdom module parameter
  64 When:   March 2010 / desktop catchup
  65
  66 Why:    This was inherited by the CONFIG_WIRELESS_OLD_REGULATORY code,
  67         and currently serves as an option for users to define an
  68         ISO / IEC 3166 alpha2 code for the country they are currently
  69         present in. Although there are userspace API replacements for this
  70         through nl80211 distributions haven't yet caught up with implementing
  71         decent alternatives through standard GUIs. Although available as an
  72         option through iw or wpa_supplicant its just a matter of time before
  73         distributions pick up good GUI options for this. The ideal solution
  74         would actually consist of intelligent designs which would do this for
  75         the user automatically even when travelling through different countries.
  76         Until then we leave this module parameter as a compromise.
  77
  78         When userspace improves with reasonable widely-available alternatives for
  79         this we will no longer need this module parameter. This entry hopes that
  80         by the super-futuristically looking date of "March 2010" we will have
  81         such replacements widely available.
  82
  83 Who:    Luis R. Rodriguez <lrodriguez@atheros.com>
  84
  85 ---------------------------
  86
  87 What:   dev->power.power_state
  88 When:   July 2007
  89 Why:    Broken design for runtime control over driver power states, confusing
  90         driver-internal runtime power management with:  mechanisms to support
  91         system-wide sleep state transitions; event codes that distinguish
  92         different phases of swsusp "sleep" transitions; and userspace policy
  93         inputs.  This framework was never widely used, and most attempts to
  94         use it were broken.  Drivers should instead be exposing domain-specific
  95         interfaces either to kernel or to userspace.
  96 Who:    Pavel Machek <pavel@ucw.cz>
  97
  98 ---------------------------
  99
 100 What:   Video4Linux obsolete drivers using V4L1 API
 101 When:   kernel 2.6.39
 102 Files:  drivers/staging/se401/* drivers/staging/usbvideo/*
 103 Check:  drivers/staging/se401/se401.c drivers/staging/usbvideo/usbvideo.c
 104 Why:    There are some drivers still using V4L1 API, despite all efforts we've done
 105         to migrate. Those drivers are for obsolete hardware that the old maintainer
 106         didn't care (or not have the hardware anymore), and that no other developer
 107         could find any hardware to buy. They probably have no practical usage today,
 108         and people with such old hardware could probably keep using an older version
 109         of the kernel. Those drivers will be moved to staging on 2.6.38 and, if nobody
 110         cares enough to port and test them with V4L2 API, they'll be removed on 2.6.39.
 111 Who:    Mauro Carvalho Chehab <mchehab@infradead.org>
 112
 113 ---------------------------
 114
 115 What:   Video4Linux: Remove obsolete ioctl's
 116 When:   kernel 2.6.39
 117 Files:  include/media/videodev2.h
 118 Why:    Some ioctl's were defined wrong on 2.6.2 and 2.6.6, using the wrong
 119         type of R/W arguments. They were fixed, but the old ioctl names are
 120         still there, maintained to avoid breaking binary compatibility:
 121           #define VIDIOC_OVERLAY_OLD    _IOWR('V', 14, int)
 122           #define VIDIOC_S_PARM_OLD     _IOW('V', 22, struct v4l2_streamparm)
 123           #define VIDIOC_S_CTRL_OLD     _IOW('V', 28, struct v4l2_control)
 124           #define VIDIOC_G_AUDIO_OLD    _IOWR('V', 33, struct v4l2_audio)
 125           #define VIDIOC_G_AUDOUT_OLD   _IOWR('V', 49, struct v4l2_audioout)
 126           #define VIDIOC_CROPCAP_OLD    _IOR('V', 58, struct v4l2_cropcap)
 127         There's no sense on preserving those forever, as it is very doubtful
 128         that someone would try to use a such old binary with a modern kernel.
 129         Removing them will allow us to remove some magic done at the V4L ioctl
 130         handler.
 131
 132 Who:    Mauro Carvalho Chehab <mchehab@infradead.org>
 133
 134 ---------------------------
 135
 136 What:   sys_sysctl
 137 When:   September 2010
 138 Option: CONFIG_SYSCTL_SYSCALL
 139 Why:    The same information is available in a more convenient from
 140         /proc/sys, and none of the sysctl variables appear to be
 141         important performance wise.
 142
 143         Binary sysctls are a long standing source of subtle kernel
 144         bugs and security issues.
 145
 146         When I looked several months ago all I could find after
 147         searching several distributions were 5 user space programs and
 148         glibc (which falls back to /proc/sys) using this syscall.
 149
 150         The man page for sysctl(2) documents it as unusable for user
 151         space programs.
 152
 153         sysctl(2) is not generally ABI compatible to a 32bit user
 154         space application on a 64bit and a 32bit kernel.
 155
 156         For the last several months the policy has been no new binary
 157         sysctls and no one has put forward an argument to use them.
 158
 159         Binary sysctls issues seem to keep happening appearing so
 160         properly deprecating them (with a warning to user space) and a
 161         2 year grace warning period will mean eventually we can kill
 162         them and end the pain.
 163
 164         In the mean time individual binary sysctls can be dealt with
 165         in a piecewise fashion.
 166
 167 Who:    Eric Biederman <ebiederm@xmission.com>
 168
 169 ---------------------------
 170
 171 What:   /proc/<pid>/oom_adj
 172 When:   August 2012
 173 Why:    /proc/<pid>/oom_adj allows userspace to influence the oom killer's
 174         badness heuristic used to determine which task to kill when the kernel
 175         is out of memory.
 176
 177         The badness heuristic has since been rewritten since the introduction of
 178         this tunable such that its meaning is deprecated.  The value was
 179         implemented as a bitshift on a score generated by the badness()
 180         function that did not have any precise units of measure.  With the
 181         rewrite, the score is given as a proportion of available memory to the
 182         task allocating pages, so using a bitshift which grows the score
 183         exponentially is, thus, impossible to tune with fine granularity.
 184
 185         A much more powerful interface, /proc/<pid>/oom_score_adj, was
 186         introduced with the oom killer rewrite that allows users to increase or
 187         decrease the badness() score linearly.  This interface will replace
 188         /proc/<pid>/oom_adj.
 189
 190         A warning will be emitted to the kernel log if an application uses this
 191         deprecated interface.  After it is printed once, future warnings will be
 192         suppressed until the kernel is rebooted.
 193
 194 ---------------------------
 195
 196 What:   remove EXPORT_SYMBOL(kernel_thread)
 197 When:   August 2006
 198 Files:  arch/*/kernel/*_ksyms.c
 199 Check:  kernel_thread
 200 Why:    kernel_thread is a low-level implementation detail.  Drivers should
 201         use the <linux/kthread.h> API instead which shields them from
 202         implementation details and provides a higherlevel interface that
 203         prevents bugs and code duplication
 204 Who:    Christoph Hellwig <hch@lst.de>
 205
 206 ---------------------------
 207
 208 What:   Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
 209         (temporary transition config option provided until then)
 210         The transition config option will also be removed at the same time.
 211 When:   before 2.6.19
 212 Why:    Unused symbols are both increasing the size of the kernel binary
 213         and are often a sign of "wrong API"
 214 Who:    Arjan van de Ven <arjan@linux.intel.com>
 215
 216 ---------------------------
 217
 218 What:   PHYSDEVPATH, PHYSDEVBUS, PHYSDEVDRIVER in the uevent environment
 219 When:   October 2008
 220 Why:    The stacking of class devices makes these values misleading and
 221         inconsistent.
 222         Class devices should not carry any of these properties, and bus
 223         devices have SUBSYTEM and DRIVER as a replacement.
 224 Who:    Kay Sievers <kay.sievers@suse.de>
 225
 226 ---------------------------
 227
 228 What:   ACPI procfs interface
 229 When:   July 2008
 230 Why:    ACPI sysfs conversion should be finished by January 2008.
 231         ACPI procfs interface will be removed in July 2008 so that
 232         there is enough time for the user space to catch up.
 233 Who:    Zhang Rui <rui.zhang@intel.com>
 234
 235 ---------------------------
 236
 237 What:   /proc/acpi/button
 238 When:   August 2007
 239 Why:    /proc/acpi/button has been replaced by events to the input layer
 240         since 2.6.20.
 241 Who:    Len Brown <len.brown@intel.com>
 242
 243 ---------------------------
 244
 245 What:   /proc/acpi/event
 246 When:   February 2008
 247 Why:    /proc/acpi/event has been replaced by events via the input layer
 248         and netlink since 2.6.23.
 249 Who:    Len Brown <len.brown@intel.com>
 250
 251 ---------------------------
 252
 253 What:   i386/x86_64 bzImage symlinks
 254 When:   April 2010
 255
 256 Why:    The i386/x86_64 merge provides a symlink to the old bzImage
 257         location so not yet updated user space tools, e.g. package
 258         scripts, do not break.
 259 Who:    Thomas Gleixner <tglx@linutronix.de>
 260
 261 ---------------------------
 262
 263 What:   GPIO autorequest on gpio_direction_{input,output}() in gpiolib
 264 When:   February 2010
 265 Why:    All callers should use explicit gpio_request()/gpio_free().
 266         The autorequest mechanism in gpiolib was provided mostly as a
 267         migration aid for legacy GPIO interfaces (for SOC based GPIOs).
 268         Those users have now largely migrated.  Platforms implementing
 269         the GPIO interfaces without using gpiolib will see no changes.
 270 Who:    David Brownell <dbrownell@users.sourceforge.net>
 271 ---------------------------
 272
 273 What:   b43 support for firmware revision < 410
 274 When:   The schedule was July 2008, but it was decided that we are going to keep the
 275         code as long as there are no major maintanance headaches.
 276         So it _could_ be removed _any_ time now, if it conflicts with something new.
 277 Why:    The support code for the old firmware hurts code readability/maintainability
 278         and slightly hurts runtime performance. Bugfixes for the old firmware
 279         are not provided by Broadcom anymore.
 280 Who:    Michael Buesch <mb@bu3sch.de>
 281
 282 ---------------------------
 283
 284 What:   /sys/o2cb symlink
 285 When:   January 2010
 286 Why:    /sys/fs/o2cb is the proper location for this information - /sys/o2cb
 287         exists as a symlink for backwards compatibility for old versions of
 288         ocfs2-tools. 2 years should be sufficient time to phase in new versions
 289         which know to look in /sys/fs/o2cb.
 290 Who:    ocfs2-devel@oss.oracle.com
 291
 292 ---------------------------
 293
 294 What:   Ability for non root users to shm_get hugetlb pages based on mlock
 295         resource limits
 296 When:   2.6.31
 297 Why:    Non root users need to be part of /proc/sys/vm/hugetlb_shm_group or
 298         have CAP_IPC_LOCK to be able to allocate shm segments backed by
 299         huge pages.  The mlock based rlimit check to allow shm hugetlb is
 300         inconsistent with mmap based allocations.  Hence it is being
 301         deprecated.
 302 Who:    Ravikiran Thirumalai <kiran@scalex86.org>
 303
 304 ---------------------------
 305
 306 What:   CONFIG_THERMAL_HWMON
 307 When:   January 2009
 308 Why:    This option was introduced just to allow older lm-sensors userspace
 309         to keep working over the upgrade to 2.6.26. At the scheduled time of
 310         removal fixed lm-sensors (2.x or 3.x) should be readily available.
 311 Who:    Rene Herman <rene.herman@gmail.com>
 312
 313 ---------------------------
 314
 315 What:   Code that is now under CONFIG_WIRELESS_EXT_SYSFS
 316         (in net/core/net-sysfs.c)
 317 When:   After the only user (hal) has seen a release with the patches
 318         for enough time, probably some time in 2010.
 319 Why:    Over 1K .text/.data size reduction, data is available in other
 320         ways (ioctls)
 321 Who:    Johannes Berg <johannes@sipsolutions.net>
 322
 323 ---------------------------
 324
 325 What:   sysfs ui for changing p4-clockmod parameters
 326 When:   September 2009
 327 Why:    See commits 129f8ae9b1b5be94517da76009ea956e89104ce8 and
 328         e088e4c9cdb618675874becb91b2fd581ee707e6.
 329         Removal is subject to fixing any remaining bugs in ACPI which may
 330         cause the thermal throttling not to happen at the right time.
 331 Who:    Dave Jones <davej@redhat.com>, Matthew Garrett <mjg@redhat.com>
 332
 333 -----------------------------
 334
 335 What:   __do_IRQ all in one fits nothing interrupt handler
 336 When:   2.6.32
 337 Why:    __do_IRQ was kept for easy migration to the type flow handlers.
 338         More than two years of migration time is enough.
 339 Who:    Thomas Gleixner <tglx@linutronix.de>
 340
 341 -----------------------------
 342
 343 What:   fakephp and associated sysfs files in /sys/bus/pci/slots/
 344 When:   2011
 345 Why:    In 2.6.27, the semantics of /sys/bus/pci/slots was redefined to
 346         represent a machine's physical PCI slots. The change in semantics
 347         had userspace implications, as the hotplug core no longer allowed
 348         drivers to create multiple sysfs files per physical slot (required
 349         for multi-function devices, e.g.). fakephp was seen as a developer's
 350         tool only, and its interface changed. Too late, we learned that
 351         there were some users of the fakephp interface.
 352
 353         In 2.6.30, the original fakephp interface was restored. At the same
 354         time, the PCI core gained the ability that fakephp provided, namely
 355         function-level hot-remove and hot-add.
 356
 357         Since the PCI core now provides the same functionality, exposed in:
 358
 359                 /sys/bus/pci/rescan
 360                 /sys/bus/pci/devices/.../remove
 361                 /sys/bus/pci/devices/.../rescan
 362
 363         there is no functional reason to maintain fakephp as well.
 364
 365         We will keep the existing module so that 'modprobe fakephp' will
 366         present the old /sys/bus/pci/slots/... interface for compatibility,
 367         but users are urged to migrate their applications to the API above.
 368
 369         After a reasonable transition period, we will remove the legacy
 370         fakephp interface.
 371 Who:    Alex Chiang <achiang@hp.com>
 372
 373 ---------------------------
 374
 375 What:   CONFIG_RFKILL_INPUT
 376 When:   2.6.33
 377 Why:    Should be implemented in userspace, policy daemon.
 378 Who:    Johannes Berg <johannes@sipsolutions.net>
 379
 380 ----------------------------
 381
 382 What:   sound-slot/service-* module aliases and related clutters in
 383         sound/sound_core.c
 384 When:   August 2010
 385 Why:    OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
 386         (14) and requests modules using custom sound-slot/service-*
 387         module aliases.  The only benefit of doing this is allowing
 388         use of custom module aliases which might as well be considered
 389         a bug at this point.  This preemptive claiming prevents
 390         alternative OSS implementations.
 391
 392         Till the feature is removed, the kernel will be requesting
 393         both sound-slot/service-* and the standard char-major-* module
 394         aliases and allow turning off the pre-claiming selectively via
 395         CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
 396         kernel parameter.
 397
 398         After the transition phase is complete, both the custom module
 399         aliases and switches to disable it will go away.  This removal
 400         will also allow making ALSA OSS emulation independent of
 401         sound_core.  The dependency will be broken then too.
 402 Who:    Tejun Heo <tj@kernel.org>
 403
 404 ----------------------------
 405
 406 What:   Support for lcd_switch and display_get in asus-laptop driver
 407 When:   March 2010
 408 Why:    These two features use non-standard interfaces. There are the
 409         only features that really need multiple path to guess what's
 410         the right method name on a specific laptop.
 411
 412         Removing them will allow to remove a lot of code an significantly
 413         clean the drivers.
 414
 415         This will affect the backlight code which won't be able to know
 416         if the backlight is on or off. The platform display file will also be
 417         write only (like the one in eeepc-laptop).
 418
 419         This should'nt affect a lot of user because they usually know
 420         when their display is on or off.
 421
 422 Who:    Corentin Chary <corentin.chary@gmail.com>
 423
 424 ----------------------------
 425
 426 What:   sysfs-class-rfkill state file
 427 When:   Feb 2014
 428 Files:  net/rfkill/core.c
 429 Why:    Documented as obsolete since Feb 2010. This file is limited to 3
 430         states while the rfkill drivers can have 4 states.
 431 Who:    anybody or Florian Mickler <florian@mickler.org>
 432
 433 ----------------------------
 434
 435 What:   sysfs-class-rfkill claim file
 436 When:   Feb 2012
 437 Files:  net/rfkill/core.c
 438 Why:    It is not possible to claim an rfkill driver since 2007. This is
 439         Documented as obsolete since Feb 2010.
 440 Who:    anybody or Florian Mickler <florian@mickler.org>
 441
 442 ----------------------------
 443
 444 What:   capifs
 445 When:   February 2011
 446 Files:  drivers/isdn/capi/capifs.*
 447 Why:    udev fully replaces this special file system that only contains CAPI
 448         NCCI TTY device nodes. User space (pppdcapiplugin) works without
 449         noticing the difference.
 450 Who:    Jan Kiszka <jan.kiszka@web.de>
 451
 452 ----------------------------
 453
 454 What:   KVM paravirt mmu host support
 455 When:   January 2011
 456 Why:    The paravirt mmu host support is slower than non-paravirt mmu, both
 457         on newer and older hardware.  It is already not exposed to the guest,
 458         and kept only for live migration purposes.
 459 Who:    Avi Kivity <avi@redhat.com>
 460
 461 ----------------------------
 462
 463 What:   iwlwifi 50XX module parameters
 464 When:   2.6.40
 465 Why:    The "..50" modules parameters were used to configure 5000 series and
 466         up devices; different set of module parameters also available for 4965
 467         with same functionalities. Consolidate both set into single place
 468         in drivers/net/wireless/iwlwifi/iwl-agn.c
 469
 470 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 471
 472 ----------------------------
 473
 474 What:   iwl4965 alias support
 475 When:   2.6.40
 476 Why:    Internal alias support has been present in module-init-tools for some
 477         time, the MODULE_ALIAS("iwl4965") boilerplate aliases can be removed
 478         with no impact.
 479
 480 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 481
 482 ---------------------------
 483
 484 What:   xt_NOTRACK
 485 Files:  net/netfilter/xt_NOTRACK.c
 486 When:   April 2011
 487 Why:    Superseded by xt_CT
 488 Who:    Netfilter developer team <netfilter-devel@vger.kernel.org>
 489
 490 ----------------------------
 491
 492 What:   IRQF_DISABLED
 493 When:   2.6.36
 494 Why:    The flag is a NOOP as we run interrupt handlers with interrupts disabled
 495 Who:    Thomas Gleixner <tglx@linutronix.de>
 496
 497 ----------------------------
 498
 499 What:   The acpi_sleep=s4_nonvs command line option
 500 When:   2.6.37
 501 Files:  arch/x86/kernel/acpi/sleep.c
 502 Why:    superseded by acpi_sleep=nonvs
 503 Who:    Rafael J. Wysocki <rjw@sisk.pl>
 504
 505 ----------------------------
 506
 507 What:   PCI DMA unmap state API
 508 When:   August 2012
 509 Why:    PCI DMA unmap state API (include/linux/pci-dma.h) was replaced
 510         with DMA unmap state API (DMA unmap state API can be used for
 511         any bus).
 512 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 513
 514 ----------------------------
 515
 516 What:   DMA_xxBIT_MASK macros
 517 When:   Jun 2011
 518 Why:    DMA_xxBIT_MASK macros were replaced with DMA_BIT_MASK() macros.
 519 Who:    FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
 520
 521 ----------------------------
 522
 523 What:   namespace cgroup (ns_cgroup)
 524 When:   2.6.38
 525 Why:    The ns_cgroup leads to some problems:
 526         * cgroup creation is out-of-control
 527         * cgroup name can conflict when pids are looping
 528         * it is not possible to have a single process handling
 529         a lot of namespaces without falling in a exponential creation time
 530         * we may want to create a namespace without creating a cgroup
 531
 532         The ns_cgroup is replaced by a compatibility flag 'clone_children',
 533         where a newly created cgroup will copy the parent cgroup values.
 534         The userspace has to manually create a cgroup and add a task to
 535         the 'tasks' file.
 536 Who:    Daniel Lezcano <daniel.lezcano@free.fr>
 537
 538 ----------------------------
 539
 540 What:   iwlwifi disable_hw_scan module parameters
 541 When:   2.6.40
 542 Why:    Hareware scan is the prefer method for iwlwifi devices for
 543         scanning operation. Remove software scan support for all the
 544         iwlwifi devices.
 545
 546 Who:    Wey-Yi Guy <wey-yi.w.guy@intel.com>
 547
 548 ----------------------------
 549
 550 What:   access to nfsd auth cache through sys_nfsservctl or '.' files
 551         in the 'nfsd' filesystem.
 552 When:   2.6.40
 553 Why:    This is a legacy interface which have been replaced by a more
 554         dynamic cache.  Continuing to maintain this interface is an
 555         unnecessary burden.
 556 Who:    NeilBrown <neilb@suse.de>
 557
 558 ----------------------------
 559
 560 What:   i2c_adapter.id
 561 When:   June 2011
 562 Why:    This field is deprecated. I2C device drivers shouldn't change their
 563         behavior based on the underlying I2C adapter. Instead, the I2C
 564         adapter driver should instantiate the I2C devices and provide the
 565         needed platform-specific information.
 566 Who:    Jean Delvare <khali@linux-fr.org>
 567
 568 ----------------------------
 569
 570 What:   cancel_rearming_delayed_work[queue]()
 571 When:   2.6.39
 572
 573 Why:    The functions have been superceded by cancel_delayed_work_sync()
 574         quite some time ago.  The conversion is trivial and there is no
 575         in-kernel user left.
 576 Who:    Tejun Heo <tj@kernel.org>
 577
 578 ----------------------------