init/Kconfig

   1 config DEFCONFIG_LIST
   2         string
   3         depends on !UML
   4         option defconfig_list
   5         default "/lib/modules/$UNAME_RELEASE/.config"
   6         default "/etc/kernel-config"
   7         default "/boot/config-$UNAME_RELEASE"
   8         default "arch/$ARCH/defconfig"
   9
  10 menu "General setup"
  11
  12 config EXPERIMENTAL
  13         bool "Prompt for development and/or incomplete code/drivers"
  14         ---help---
  15           Some of the various things that Linux supports (such as network
  16           drivers, file systems, network protocols, etc.) can be in a state
  17           of development where the functionality, stability, or the level of
  18           testing is not yet high enough for general use. This is usually
  19           known as the "alpha-test" phase among developers. If a feature is
  20           currently in alpha-test, then the developers usually discourage
  21           uninformed widespread use of this feature by the general public to
  22           avoid "Why doesn't this work?" type mail messages. However, active
  23           testing and use of these systems is welcomed. Just be aware that it
  24           may not meet the normal level of reliability or it may fail to work
  25           in some special cases. Detailed bug reports from people familiar
  26           with the kernel internals are usually welcomed by the developers
  27           (before submitting bug reports, please read the documents
  28           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  29           <file:Documentation/BUG-HUNTING>, and
  30           <file:Documentation/oops-tracing.txt> in the kernel source).
  31
  32           This option will also make obsoleted drivers available. These are
  33           drivers that have been replaced by something else, and/or are
  34           scheduled to be removed in a future kernel release.
  35
  36           Unless you intend to help test and develop a feature or driver that
  37           falls into this category, or you have a situation that requires
  38           using these features, you should probably say N here, which will
  39           cause the configurator to present you with fewer choices. If
  40           you say Y here, you will be offered the choice of using features or
  41           drivers that are currently considered to be in the alpha-test phase.
  42
  43 config BROKEN
  44         bool
  45
  46 config BROKEN_ON_SMP
  47         bool
  48         depends on BROKEN || !SMP
  49         default y
  50
  51 config LOCK_KERNEL
  52         bool
  53         depends on SMP || PREEMPT
  54         default y
  55
  56 config INIT_ENV_ARG_LIMIT
  57         int
  58         default 32 if !UML
  59         default 128 if UML
  60         help
  61           Maximum of each of the number of arguments and environment
  62           variables passed to init from the kernel command line.
  63
  64
  65 config LOCALVERSION
  66         string "Local version - append to kernel release"
  67         help
  68           Append an extra string to the end of your kernel version.
  69           This will show up when you type uname, for example.
  70           The string you set here will be appended after the contents of
  71           any files with a filename matching localversion* in your
  72           object and source tree, in that order.  Your total string can
  73           be a maximum of 64 characters.
  74
  75 config LOCALVERSION_AUTO
  76         bool "Automatically append version information to the version string"
  77         default y
  78         help
  79           This will try to automatically determine if the current tree is a
  80           release tree by looking for git tags that belong to the current
  81           top of tree revision.
  82
  83           A string of the format -gxxxxxxxx will be added to the localversion
  84           if a git-based tree is found.  The string generated by this will be
  85           appended after any matching localversion* files, and after the value
  86           set in CONFIG_LOCALVERSION.
  87
  88           (The actual string used here is the first eight characters produced
  89           by running the command:
  90
  91             $ git rev-parse --verify HEAD
  92
  93           which is done within the script "scripts/setlocalversion".)
  94
  95 config SWAP
  96         bool "Support for paging of anonymous memory (swap)"
  97         depends on MMU && BLOCK
  98         default y
  99         help
 100           This option allows you to choose whether you want to have support
 101           for so called swap devices or swap files in your kernel that are
 102           used to provide more virtual memory than the actual RAM present
 103           in your computer.  If unsure say Y.
 104
 105 config SYSVIPC
 106         bool "System V IPC"
 107         ---help---
 108           Inter Process Communication is a suite of library functions and
 109           system calls which let processes (running programs) synchronize and
 110           exchange information. It is generally considered to be a good thing,
 111           and some programs won't run unless you say Y here. In particular, if
 112           you want to run the DOS emulator dosemu under Linux (read the
 113           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 114           you'll need to say Y here.
 115
 116           You can find documentation about IPC with "info ipc" and also in
 117           section 6.4 of the Linux Programmer's Guide, available from
 118           <http://www.tldp.org/guides.html>.
 119
 120 config SYSVIPC_SYSCTL
 121         bool
 122         depends on SYSVIPC
 123         depends on SYSCTL
 124         default y
 125
 126 config POSIX_MQUEUE
 127         bool "POSIX Message Queues"
 128         depends on NET && EXPERIMENTAL
 129         ---help---
 130           POSIX variant of message queues is a part of IPC. In POSIX message
 131           queues every message has a priority which decides about succession
 132           of receiving it by a process. If you want to compile and run
 133           programs written e.g. for Solaris with use of its POSIX message
 134           queues (functions mq_*) say Y here.
 135
 136           POSIX message queues are visible as a filesystem called 'mqueue'
 137           and can be mounted somewhere if you want to do filesystem
 138           operations on message queues.
 139
 140           If unsure, say Y.
 141
 142 config BSD_PROCESS_ACCT
 143         bool "BSD Process Accounting"
 144         help
 145           If you say Y here, a user level program will be able to instruct the
 146           kernel (via a special system call) to write process accounting
 147           information to a file: whenever a process exits, information about
 148           that process will be appended to the file by the kernel.  The
 149           information includes things such as creation time, owning user,
 150           command name, memory usage, controlling terminal etc. (the complete
 151           list is in the struct acct in <file:include/linux/acct.h>).  It is
 152           up to the user level program to do useful things with this
 153           information.  This is generally a good idea, so say Y.
 154
 155 config BSD_PROCESS_ACCT_V3
 156         bool "BSD Process Accounting version 3 file format"
 157         depends on BSD_PROCESS_ACCT
 158         default n
 159         help
 160           If you say Y here, the process accounting information is written
 161           in a new file format that also logs the process IDs of each
 162           process and it's parent. Note that this file format is incompatible
 163           with previous v0/v1/v2 file formats, so you will need updated tools
 164           for processing it. A preliminary version of these tools is available
 165           at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
 166
 167 config TASKSTATS
 168         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 169         depends on NET
 170         default n
 171         help
 172           Export selected statistics for tasks/processes through the
 173           generic netlink interface. Unlike BSD process accounting, the
 174           statistics are available during the lifetime of tasks/processes as
 175           responses to commands. Like BSD accounting, they are sent to user
 176           space on task exit.
 177
 178           Say N if unsure.
 179
 180 config TASK_DELAY_ACCT
 181         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 182         depends on TASKSTATS
 183         help
 184           Collect information on time spent by a task waiting for system
 185           resources like cpu, synchronous block I/O completion and swapping
 186           in pages. Such statistics can help in setting a task's priorities
 187           relative to other tasks for cpu, io, rss limits etc.
 188
 189           Say N if unsure.
 190
 191 config TASK_XACCT
 192         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 193         depends on TASKSTATS
 194         help
 195           Collect extended task accounting data and send the data
 196           to userland for processing over the taskstats interface.
 197
 198           Say N if unsure.
 199
 200 config TASK_IO_ACCOUNTING
 201         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 202         depends on TASK_XACCT
 203         help
 204           Collect information on the number of bytes of storage I/O which this
 205           task has caused.
 206
 207           Say N if unsure.
 208
 209 config USER_NS
 210         bool "User Namespaces (EXPERIMENTAL)"
 211         default n
 212         depends on EXPERIMENTAL
 213         help
 214           Support user namespaces.  This allows containers, i.e.
 215           vservers, to use user namespaces to provide different
 216           user info for different servers.  If unsure, say N.
 217
 218 config AUDIT
 219         bool "Auditing support"
 220         depends on NET
 221         help
 222           Enable auditing infrastructure that can be used with another
 223           kernel subsystem, such as SELinux (which requires this for
 224           logging of avc messages output).  Does not do system-call
 225           auditing without CONFIG_AUDITSYSCALL.
 226
 227 config AUDITSYSCALL
 228         bool "Enable system-call auditing support"
 229         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64)
 230         default y if SECURITY_SELINUX
 231         help
 232           Enable low-overhead system-call auditing infrastructure that
 233           can be used independently or with another kernel subsystem,
 234           such as SELinux.  To use audit's filesystem watch feature, please
 235           ensure that INOTIFY is configured.
 236
 237 config IKCONFIG
 238         tristate "Kernel .config support"
 239         ---help---
 240           This option enables the complete Linux kernel ".config" file
 241           contents to be saved in the kernel. It provides documentation
 242           of which kernel options are used in a running kernel or in an
 243           on-disk kernel.  This information can be extracted from the kernel
 244           image file with the script scripts/extract-ikconfig and used as
 245           input to rebuild the current kernel or to build another kernel.
 246           It can also be extracted from a running kernel by reading
 247           /proc/config.gz if enabled (below).
 248
 249 config IKCONFIG_PROC
 250         bool "Enable access to .config through /proc/config.gz"
 251         depends on IKCONFIG && PROC_FS
 252         ---help---
 253           This option enables access to the kernel configuration file
 254           through /proc/config.gz.
 255
 256 config LOG_BUF_SHIFT
 257         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 258         range 12 21
 259         default 17 if S390 || LOCKDEP
 260         default 16 if X86_NUMAQ || IA64
 261         default 15 if SMP
 262         default 14
 263         help
 264           Select kernel log buffer size as a power of 2.
 265           Defaults and Examples:
 266                      17 => 128 KB for S/390
 267                      16 => 64 KB for x86 NUMAQ or IA-64
 268                      15 => 32 KB for SMP
 269                      14 => 16 KB for uniprocessor
 270                      13 =>  8 KB
 271                      12 =>  4 KB
 272
 273 config CGROUPS
 274         bool "Control Group support"
 275         help
 276           This option will let you use process cgroup subsystems
 277           such as Cpusets
 278
 279           Say N if unsure.
 280
 281 config CGROUP_DEBUG
 282         bool "Example debug cgroup subsystem"
 283         depends on CGROUPS
 284         help
 285           This option enables a simple cgroup subsystem that
 286           exports useful debugging information about the cgroups
 287           framework
 288
 289           Say N if unsure
 290
 291 config CPUSETS
 292         bool "Cpuset support"
 293         depends on SMP && CGROUPS
 294         help
 295           This option will let you create and manage CPUSETs which
 296           allow dynamically partitioning a system into sets of CPUs and
 297           Memory Nodes and assigning tasks to run only within those sets.
 298           This is primarily useful on large SMP or NUMA systems.
 299
 300           Say N if unsure.
 301
 302 config FAIR_GROUP_SCHED
 303         bool "Fair group CPU scheduler"
 304         default y
 305         depends on EXPERIMENTAL
 306         help
 307           This feature lets CPU scheduler recognize task groups and control CPU
 308           bandwidth allocation to such task groups.
 309
 310 choice
 311         depends on FAIR_GROUP_SCHED
 312         prompt "Basis for grouping tasks"
 313         default FAIR_USER_SCHED
 314
 315 config FAIR_USER_SCHED
 316         bool "user id"
 317         help
 318           This option will choose userid as the basis for grouping
 319           tasks, thus providing equal CPU bandwidth to each user.
 320
 321 endchoice
 322
 323 config SYSFS_DEPRECATED
 324         bool "Create deprecated sysfs files"
 325         default y
 326         help
 327           This option creates deprecated symlinks such as the
 328           "device"-link, the <subsystem>:<name>-link, and the
 329           "bus"-link. It may also add deprecated key in the
 330           uevent environment.
 331           None of these features or values should be used today, as
 332           they export driver core implementation details to userspace
 333           or export properties which can't be kept stable across kernel
 334           releases.
 335
 336           If enabled, this option will also move any device structures
 337           that belong to a class, back into the /sys/class hierarchy, in
 338           order to support older versions of udev.
 339
 340           If you are using a distro that was released in 2006 or later,
 341           it should be safe to say N here.
 342
 343 config PROC_PID_CPUSET
 344         bool "Include legacy /proc/<pid>/cpuset file"
 345         depends on CPUSETS
 346         default y
 347
 348 config CGROUP_CPUACCT
 349         bool "Simple CPU accounting cgroup subsystem"
 350         depends on CGROUPS
 351         help
 352           Provides a simple Resource Controller for monitoring the
 353           total CPU consumed by the tasks in a cgroup
 354
 355 config RELAY
 356         bool "Kernel->user space relay support (formerly relayfs)"
 357         help
 358           This option enables support for relay interface support in
 359           certain file systems (such as debugfs).
 360           It is designed to provide an efficient mechanism for tools and
 361           facilities to relay large amounts of data from kernel space to
 362           user space.
 363
 364           If unsure, say N.
 365
 366 config BLK_DEV_INITRD
 367         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 368         depends on BROKEN || !FRV
 369         help
 370           The initial RAM filesystem is a ramfs which is loaded by the
 371           boot loader (loadlin or lilo) and that is mounted as root
 372           before the normal boot procedure. It is typically used to
 373           load modules needed to mount the "real" root file system,
 374           etc. See <file:Documentation/initrd.txt> for details.
 375
 376           If RAM disk support (BLK_DEV_RAM) is also included, this
 377           also enables initial RAM disk (initrd) support and adds
 378           15 Kbytes (more on some other architectures) to the kernel size.
 379
 380           If unsure say Y.
 381
 382 if BLK_DEV_INITRD
 383
 384 source "usr/Kconfig"
 385
 386 endif
 387
 388 config CC_OPTIMIZE_FOR_SIZE
 389         bool "Optimize for size (Look out for broken compilers!)"
 390         default y
 391         depends on ARM || H8300 || SUPERH || EXPERIMENTAL
 392         help
 393           Enabling this option will pass "-Os" instead of "-O2" to gcc
 394           resulting in a smaller kernel.
 395
 396           WARNING: some versions of gcc may generate incorrect code with this
 397           option.  If problems are observed, a gcc upgrade may be needed.
 398
 399           If unsure, say N.
 400
 401 config SYSCTL
 402         bool
 403
 404 menuconfig EMBEDDED
 405         bool "Configure standard kernel features (for small systems)"
 406         help
 407           This option allows certain base kernel options and settings
 408           to be disabled or tweaked. This is for specialized
 409           environments which can tolerate a "non-standard" kernel.
 410           Only use this if you really know what you are doing.
 411
 412 config UID16
 413         bool "Enable 16-bit UID system calls" if EMBEDDED
 414         depends on ARM || BFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
 415         default y
 416         help
 417           This enables the legacy 16-bit UID syscall wrappers.
 418
 419 config SYSCTL_SYSCALL
 420         bool "Sysctl syscall support" if EMBEDDED
 421         default y
 422         select SYSCTL
 423         ---help---
 424           sys_sysctl uses binary paths that have been found challenging
 425           to properly maintain and use.  The interface in /proc/sys
 426           using paths with ascii names is now the primary path to this
 427           information.
 428
 429           Almost nothing using the binary sysctl interface so if you are
 430           trying to save some space it is probably safe to disable this,
 431           making your kernel marginally smaller.
 432
 433           If unsure say Y here.
 434
 435 config KALLSYMS
 436          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 437          default y
 438          help
 439            Say Y here to let the kernel print out symbolic crash information and
 440            symbolic stack backtraces. This increases the size of the kernel
 441            somewhat, as all symbols have to be loaded into the kernel image.
 442
 443 config KALLSYMS_ALL
 444         bool "Include all symbols in kallsyms"
 445         depends on DEBUG_KERNEL && KALLSYMS
 446         help
 447            Normally kallsyms only contains the symbols of functions, for nicer
 448            OOPS messages.  Some debuggers can use kallsyms for other
 449            symbols too: say Y here to include all symbols, if you need them
 450            and you don't care about adding 300k to the size of your kernel.
 451
 452            Say N.
 453
 454 config KALLSYMS_EXTRA_PASS
 455         bool "Do an extra kallsyms pass"
 456         depends on KALLSYMS
 457         help
 458            If kallsyms is not working correctly, the build will fail with
 459            inconsistent kallsyms data.  If that occurs, log a bug report and
 460            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 461            Always say N here unless you find a bug in kallsyms, which must be
 462            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 463            you wait for kallsyms to be fixed.
 464
 465
 466 config HOTPLUG
 467         bool "Support for hot-pluggable devices" if EMBEDDED
 468         default y
 469         help
 470           This option is provided for the case where no hotplug or uevent
 471           capabilities is wanted by the kernel.  You should only consider
 472           disabling this option for embedded systems that do not use modules, a
 473           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 474
 475 config PRINTK
 476         default y
 477         bool "Enable support for printk" if EMBEDDED
 478         help
 479           This option enables normal printk support. Removing it
 480           eliminates most of the message strings from the kernel image
 481           and makes the kernel more or less silent. As this makes it
 482           very difficult to diagnose system problems, saying N here is
 483           strongly discouraged.
 484
 485 config BUG
 486         bool "BUG() support" if EMBEDDED
 487         default y
 488         help
 489           Disabling this option eliminates support for BUG and WARN, reducing
 490           the size of your kernel image and potentially quietly ignoring
 491           numerous fatal conditions. You should only consider disabling this
 492           option for embedded systems with no facilities for reporting errors.
 493           Just say Y.
 494
 495 config ELF_CORE
 496         default y
 497         bool "Enable ELF core dumps" if EMBEDDED
 498         help
 499           Enable support for generating core dumps. Disabling saves about 4k.
 500
 501 config BASE_FULL
 502         default y
 503         bool "Enable full-sized data structures for core" if EMBEDDED
 504         help
 505           Disabling this option reduces the size of miscellaneous core
 506           kernel data structures. This saves memory on small machines,
 507           but may reduce performance.
 508
 509 config FUTEX
 510         bool "Enable futex support" if EMBEDDED
 511         default y
 512         select RT_MUTEXES
 513         help
 514           Disabling this option will cause the kernel to be built without
 515           support for "fast userspace mutexes".  The resulting kernel may not
 516           run glibc-based applications correctly.
 517
 518 config ANON_INODES
 519         bool
 520
 521 config EPOLL
 522         bool "Enable eventpoll support" if EMBEDDED
 523         default y
 524         select ANON_INODES
 525         help
 526           Disabling this option will cause the kernel to be built without
 527           support for epoll family of system calls.
 528
 529 config SIGNALFD
 530         bool "Enable signalfd() system call" if EMBEDDED
 531         select ANON_INODES
 532         default y
 533         help
 534           Enable the signalfd() system call that allows to receive signals
 535           on a file descriptor.
 536
 537           If unsure, say Y.
 538
 539 config TIMERFD
 540         bool "Enable timerfd() system call" if EMBEDDED
 541         select ANON_INODES
 542         depends on BROKEN
 543         default y
 544         help
 545           Enable the timerfd() system call that allows to receive timer
 546           events on a file descriptor.
 547
 548           If unsure, say Y.
 549
 550 config EVENTFD
 551         bool "Enable eventfd() system call" if EMBEDDED
 552         select ANON_INODES
 553         default y
 554         help
 555           Enable the eventfd() system call that allows to receive both
 556           kernel notification (ie. KAIO) or userspace notifications.
 557
 558           If unsure, say Y.
 559
 560 config SHMEM
 561         bool "Use full shmem filesystem" if EMBEDDED
 562         default y
 563         depends on MMU
 564         help
 565           The shmem is an internal filesystem used to manage shared memory.
 566           It is backed by swap and manages resource limits. It is also exported
 567           to userspace as tmpfs if TMPFS is enabled. Disabling this
 568           option replaces shmem and tmpfs with the much simpler ramfs code,
 569           which may be appropriate on small systems without swap.
 570
 571 config VM_EVENT_COUNTERS
 572         default y
 573         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 574         help
 575           VM event counters are needed for event counts to be shown.
 576           This option allows the disabling of the VM event counters
 577           on EMBEDDED systems.  /proc/vmstat will only show page counts
 578           if VM event counters are disabled.
 579
 580 config SLUB_DEBUG
 581         default y
 582         bool "Enable SLUB debugging support" if EMBEDDED
 583         depends on SLUB
 584         help
 585           SLUB has extensive debug support features. Disabling these can
 586           result in significant savings in code size. This also disables
 587           SLUB sysfs support. /sys/slab will not exist and there will be
 588           no support for cache validation etc.
 589
 590 choice
 591         prompt "Choose SLAB allocator"
 592         default SLUB
 593         help
 594            This option allows to select a slab allocator.
 595
 596 config SLAB
 597         bool "SLAB"
 598         help
 599           The regular slab allocator that is established and known to work
 600           well in all environments. It organizes cache hot objects in
 601           per cpu and per node queues. SLAB is the default choice for
 602           a slab allocator.
 603
 604 config SLUB
 605         bool "SLUB (Unqueued Allocator)"
 606         help
 607            SLUB is a slab allocator that minimizes cache line usage
 608            instead of managing queues of cached objects (SLAB approach).
 609            Per cpu caching is realized using slabs of objects instead
 610            of queues of objects. SLUB can use memory efficiently
 611            and has enhanced diagnostics.
 612
 613 config SLOB
 614         depends on EMBEDDED
 615         bool "SLOB (Simple Allocator)"
 616         help
 617            SLOB replaces the SLAB allocator with a drastically simpler
 618            allocator.  SLOB is more space efficient than SLAB but does not
 619            scale well (single lock for all operations) and is also highly
 620            susceptible to fragmentation. SLUB can accomplish a higher object
 621            density. It is usually better to use SLUB instead of SLOB.
 622
 623 endchoice
 624
 625 endmenu         # General setup
 626
 627 config RT_MUTEXES
 628         boolean
 629         select PLIST
 630
 631 config TINY_SHMEM
 632         default !SHMEM
 633         bool
 634
 635 config BASE_SMALL
 636         int
 637         default 0 if BASE_FULL
 638         default 1 if !BASE_FULL
 639
 640 menuconfig MODULES
 641         bool "Enable loadable module support"
 642         help
 643           Kernel modules are small pieces of compiled code which can
 644           be inserted in the running kernel, rather than being
 645           permanently built into the kernel.  You use the "modprobe"
 646           tool to add (and sometimes remove) them.  If you say Y here,
 647           many parts of the kernel can be built as modules (by
 648           answering M instead of Y where indicated): this is most
 649           useful for infrequently used options which are not required
 650           for booting.  For more information, see the man pages for
 651           modprobe, lsmod, modinfo, insmod and rmmod.
 652
 653           If you say Y here, you will need to run "make
 654           modules_install" to put the modules under /lib/modules/
 655           where modprobe can find them (you may need to be root to do
 656           this).
 657
 658           If unsure, say Y.
 659
 660 config MODULE_UNLOAD
 661         bool "Module unloading"
 662         depends on MODULES
 663         help
 664           Without this option you will not be able to unload any
 665           modules (note that some modules may not be unloadable
 666           anyway), which makes your kernel slightly smaller and
 667           simpler.  If unsure, say Y.
 668
 669 config MODULE_FORCE_UNLOAD
 670         bool "Forced module unloading"
 671         depends on MODULE_UNLOAD && EXPERIMENTAL
 672         help
 673           This option allows you to force a module to unload, even if the
 674           kernel believes it is unsafe: the kernel will remove the module
 675           without waiting for anyone to stop using it (using the -f option to
 676           rmmod).  This is mainly for kernel developers and desperate users.
 677           If unsure, say N.
 678
 679 config MODVERSIONS
 680         bool "Module versioning support"
 681         depends on MODULES
 682         help
 683           Usually, you have to use modules compiled with your kernel.
 684           Saying Y here makes it sometimes possible to use modules
 685           compiled for different kernels, by adding enough information
 686           to the modules to (hopefully) spot any changes which would
 687           make them incompatible with the kernel you are running.  If
 688           unsure, say N.
 689
 690 config MODULE_SRCVERSION_ALL
 691         bool "Source checksum for all modules"
 692         depends on MODULES
 693         help
 694           Modules which contain a MODULE_VERSION get an extra "srcversion"
 695           field inserted into their modinfo section, which contains a
 696           sum of the source files which made it.  This helps maintainers
 697           see exactly which source was used to build a module (since
 698           others sometimes change the module source without updating
 699           the version).  With this option, such a "srcversion" field
 700           will be created for all modules.  If unsure, say N.
 701
 702 config KMOD
 703         bool "Automatic kernel module loading"
 704         depends on MODULES
 705         help
 706           Normally when you have selected some parts of the kernel to
 707           be created as kernel modules, you must load them (using the
 708           "modprobe" command) before you can use them. If you say Y
 709           here, some parts of the kernel will be able to load modules
 710           automatically: when a part of the kernel needs a module, it
 711           runs modprobe with the appropriate arguments, thereby
 712           loading the module if it is available.  If unsure, say Y.
 713
 714 config STOP_MACHINE
 715         bool
 716         default y
 717         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 718         help
 719           Need stop_machine() primitive.
 720
 721 source "block/Kconfig"
 722
 723 config PREEMPT_NOTIFIERS
 724         bool