lib/Kconfig.debug

   1
   2 config PRINTK_TIME
   3         bool "Show timing information on printks"
   4         depends on PRINTK
   5         help
   6           Selecting this option causes time stamps of the printk()
   7           messages to be added to the output of the syslog() system
   8           call and at the console.
   9
  10           The timestamp is always recorded internally, and exported
  11           to /dev/kmsg. This flag just specifies if the timestamp should
  12           be included, not that the timestamp is recorded.
  13
  14           The behavior is also controlled by the kernel command line
  15           parameter printk.time=1. See Documentation/kernel-parameters.txt
  16
  17 config DEFAULT_MESSAGE_LOGLEVEL
  18         int "Default message log level (1-7)"
  19         range 1 7
  20         default "4"
  21         help
  22           Default log level for printk statements with no specified priority.
  23
  24           This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
  25           that are auditing their logs closely may want to set it to a lower
  26           priority.
  27
  28 config ENABLE_WARN_DEPRECATED
  29         bool "Enable __deprecated logic"
  30         default y
  31         help
  32           Enable the __deprecated logic in the kernel build.
  33           Disable this to suppress the "warning: 'foo' is deprecated
  34           (declared at kernel/power/somefile.c:1234)" messages.
  35
  36 config ENABLE_MUST_CHECK
  37         bool "Enable __must_check logic"
  38         default y
  39         help
  40           Enable the __must_check logic in the kernel build.  Disable this to
  41           suppress the "warning: ignoring return value of 'foo', declared with
  42           attribute warn_unused_result" messages.
  43
  44 config FRAME_WARN
  45         int "Warn for stack frames larger than (needs gcc 4.4)"
  46         range 0 8192
  47         default 1024 if !64BIT
  48         default 2048 if 64BIT
  49         help
  50           Tell gcc to warn at build time for stack frames larger than this.
  51           Setting this too low will cause a lot of warnings.
  52           Setting it to 0 disables the warning.
  53           Requires gcc 4.4
  54
  55 config MAGIC_SYSRQ
  56         bool "Magic SysRq key"
  57         depends on !UML
  58         help
  59           If you say Y here, you will have some control over the system even
  60           if the system crashes for example during kernel debugging (e.g., you
  61           will be able to flush the buffer cache to disk, reboot the system
  62           immediately or dump some status information). This is accomplished
  63           by pressing various keys while holding SysRq (Alt+PrintScreen). It
  64           also works on a serial console (on PC hardware at least), if you
  65           send a BREAK and then within 5 seconds a command keypress. The
  66           keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
  67           unless you really know what this hack does.
  68
  69 config STRIP_ASM_SYMS
  70         bool "Strip assembler-generated symbols during link"
  71         default n
  72         help
  73           Strip internal assembler-generated symbols during a link (symbols
  74           that look like '.Lxxx') so they don't pollute the output of
  75           get_wchan() and suchlike.
  76
  77 config UNUSED_SYMBOLS
  78         bool "Enable unused/obsolete exported symbols"
  79         default y if X86
  80         help
  81           Unused but exported symbols make the kernel needlessly bigger.  For
  82           that reason most of these unused exports will soon be removed.  This
  83           option is provided temporarily to provide a transition period in case
  84           some external kernel module needs one of these symbols anyway. If you
  85           encounter such a case in your module, consider if you are actually
  86           using the right API.  (rationale: since nobody in the kernel is using
  87           this in a module, there is a pretty good chance it's actually the
  88           wrong interface to use).  If you really need the symbol, please send a
  89           mail to the linux kernel mailing list mentioning the symbol and why
  90           you really need it, and what the merge plan to the mainline kernel for
  91           your module is.
  92
  93 config DEBUG_FS
  94         bool "Debug Filesystem"
  95         help
  96           debugfs is a virtual file system that kernel developers use to put
  97           debugging files into.  Enable this option to be able to read and
  98           write to these files.
  99
 100           For detailed documentation on the debugfs API, see
 101           Documentation/DocBook/filesystems.
 102
 103           If unsure, say N.
 104
 105 config HEADERS_CHECK
 106         bool "Run 'make headers_check' when building vmlinux"
 107         depends on !UML
 108         help
 109           This option will extract the user-visible kernel headers whenever
 110           building the kernel, and will run basic sanity checks on them to
 111           ensure that exported files do not attempt to include files which
 112           were not exported, etc.
 113
 114           If you're making modifications to header files which are
 115           relevant for userspace, say 'Y', and check the headers
 116           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
 117           your build tree), to make sure they're suitable.
 118
 119 config DEBUG_SECTION_MISMATCH
 120         bool "Enable full Section mismatch analysis"
 121         help
 122           The section mismatch analysis checks if there are illegal
 123           references from one section to another section.
 124           During linktime or runtime, some sections are dropped;
 125           any use of code/data previously in these sections would
 126           most likely result in an oops.
 127           In the code, functions and variables are annotated with
 128           __init, __devinit, etc. (see the full list in include/linux/init.h),
 129           which results in the code/data being placed in specific sections.
 130           The section mismatch analysis is always performed after a full
 131           kernel build, and enabling this option causes the following
 132           additional steps to occur:
 133           - Add the option -fno-inline-functions-called-once to gcc commands.
 134             When inlining a function annotated with __init in a non-init
 135             function, we would lose the section information and thus
 136             the analysis would not catch the illegal reference.
 137             This option tells gcc to inline less (but it does result in
 138             a larger kernel).
 139           - Run the section mismatch analysis for each module/built-in.o file.
 140             When we run the section mismatch analysis on vmlinux.o, we
 141             lose valueble information about where the mismatch was
 142             introduced.
 143             Running the analysis for each module/built-in.o file
 144             tells where the mismatch happens much closer to the
 145             source. The drawback is that the same mismatch is
 146             reported at least twice.
 147           - Enable verbose reporting from modpost in order to help resolve
 148             the section mismatches that are reported.
 149
 150 config DEBUG_KERNEL
 151         bool "Kernel debugging"
 152         help
 153           Say Y here if you are developing drivers or trying to debug and
 154           identify kernel problems.
 155
 156 config DEBUG_SHIRQ
 157         bool "Debug shared IRQ handlers"
 158         depends on DEBUG_KERNEL && GENERIC_HARDIRQS
 159         help
 160           Enable this to generate a spurious interrupt as soon as a shared
 161           interrupt handler is registered, and just before one is deregistered.
 162           Drivers ought to be able to handle interrupts coming in at those
 163           points; some don't and need to be caught.
 164
 165 config LOCKUP_DETECTOR
 166         bool "Detect Hard and Soft Lockups"
 167         depends on DEBUG_KERNEL && !S390
 168         help
 169           Say Y here to enable the kernel to act as a watchdog to detect
 170           hard and soft lockups.
 171
 172           Softlockups are bugs that cause the kernel to loop in kernel
 173           mode for more than 20 seconds, without giving other tasks a
 174           chance to run.  The current stack trace is displayed upon
 175           detection and the system will stay locked up.
 176
 177           Hardlockups are bugs that cause the CPU to loop in kernel mode
 178           for more than 10 seconds, without letting other interrupts have a
 179           chance to run.  The current stack trace is displayed upon detection
 180           and the system will stay locked up.
 181
 182           The overhead should be minimal.  A periodic hrtimer runs to
 183           generate interrupts and kick the watchdog task every 4 seconds.
 184           An NMI is generated every 10 seconds or so to check for hardlockups.
 185
 186           The frequency of hrtimer and NMI events and the soft and hard lockup
 187           thresholds can be controlled through the sysctl watchdog_thresh.
 188
 189 config HARDLOCKUP_DETECTOR
 190         def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
 191                  !HAVE_NMI_WATCHDOG
 192
 193 config BOOTPARAM_HARDLOCKUP_PANIC
 194         bool "Panic (Reboot) On Hard Lockups"
 195         depends on LOCKUP_DETECTOR
 196         help
 197           Say Y here to enable the kernel to panic on "hard lockups",
 198           which are bugs that cause the kernel to loop in kernel
 199           mode with interrupts disabled for more than 10 seconds (configurable
 200           using the watchdog_thresh sysctl).
 201
 202           Say N if unsure.
 203
 204 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
 205         int
 206         depends on LOCKUP_DETECTOR
 207         range 0 1
 208         default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
 209         default 1 if BOOTPARAM_HARDLOCKUP_PANIC
 210
 211 config BOOTPARAM_SOFTLOCKUP_PANIC
 212         bool "Panic (Reboot) On Soft Lockups"
 213         depends on LOCKUP_DETECTOR
 214         help
 215           Say Y here to enable the kernel to panic on "soft lockups",
 216           which are bugs that cause the kernel to loop in kernel
 217           mode for more than 20 seconds (configurable using the watchdog_thresh
 218           sysctl), without giving other tasks a chance to run.
 219
 220           The panic can be used in combination with panic_timeout,
 221           to cause the system to reboot automatically after a
 222           lockup has been detected. This feature is useful for
 223           high-availability systems that have uptime guarantees and
 224           where a lockup must be resolved ASAP.
 225
 226           Say N if unsure.
 227
 228 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
 229         int
 230         depends on LOCKUP_DETECTOR
 231         range 0 1
 232         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
 233         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 234
 235 config DETECT_HUNG_TASK
 236         bool "Detect Hung Tasks"
 237         depends on DEBUG_KERNEL
 238         default LOCKUP_DETECTOR
 239         help
 240           Say Y here to enable the kernel to detect "hung tasks",
 241           which are bugs that cause the task to be stuck in
 242           uninterruptible "D" state indefinitiley.
 243
 244           When a hung task is detected, the kernel will print the
 245           current stack trace (which you should report), but the
 246           task will stay in uninterruptible state. If lockdep is
 247           enabled then all held locks will also be reported. This
 248           feature has negligible overhead.
 249
 250 config DEFAULT_HUNG_TASK_TIMEOUT
 251         int "Default timeout for hung task detection (in seconds)"
 252         depends on DETECT_HUNG_TASK
 253         default 120
 254         help
 255           This option controls the default timeout (in seconds) used
 256           to determine when a task has become non-responsive and should
 257           be considered hung.
 258
 259           It can be adjusted at runtime via the kernel.hung_task_timeout_secs
 260           sysctl or by writing a value to
 261           /proc/sys/kernel/hung_task_timeout_secs.
 262
 263           A timeout of 0 disables the check.  The default is two minutes.
 264           Keeping the default should be fine in most cases.
 265
 266 config BOOTPARAM_HUNG_TASK_PANIC
 267         bool "Panic (Reboot) On Hung Tasks"
 268         depends on DETECT_HUNG_TASK
 269         help
 270           Say Y here to enable the kernel to panic on "hung tasks",
 271           which are bugs that cause the kernel to leave a task stuck
 272           in uninterruptible "D" state.
 273
 274           The panic can be used in combination with panic_timeout,
 275           to cause the system to reboot automatically after a
 276           hung task has been detected. This feature is useful for
 277           high-availability systems that have uptime guarantees and
 278           where a hung tasks must be resolved ASAP.
 279
 280           Say N if unsure.
 281
 282 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
 283         int
 284         depends on DETECT_HUNG_TASK
 285         range 0 1
 286         default 0 if !BOOTPARAM_HUNG_TASK_PANIC
 287         default 1 if BOOTPARAM_HUNG_TASK_PANIC
 288
 289 config SCHED_DEBUG
 290         bool "Collect scheduler debugging info"
 291         depends on DEBUG_KERNEL && PROC_FS
 292         default y
 293         help
 294           If you say Y here, the /proc/sched_debug file will be provided
 295           that can help debug the scheduler. The runtime overhead of this
 296           option is minimal.
 297
 298 config SCHEDSTATS
 299         bool "Collect scheduler statistics"
 300         depends on DEBUG_KERNEL && PROC_FS
 301         help
 302           If you say Y here, additional code will be inserted into the
 303           scheduler and related routines to collect statistics about
 304           scheduler behavior and provide them in /proc/schedstat.  These
 305           stats may be useful for both tuning and debugging the scheduler
 306           If you aren't debugging the scheduler or trying to tune a specific
 307           application, you can say N to avoid the very slight overhead
 308           this adds.
 309
 310 config TIMER_STATS
 311         bool "Collect kernel timers statistics"
 312         depends on DEBUG_KERNEL && PROC_FS
 313         help
 314           If you say Y here, additional code will be inserted into the
 315           timer routines to collect statistics about kernel timers being
 316           reprogrammed. The statistics can be read from /proc/timer_stats.
 317           The statistics collection is started by writing 1 to /proc/timer_stats,
 318           writing 0 stops it. This feature is useful to collect information
 319           about timer usage patterns in kernel and userspace. This feature
 320           is lightweight if enabled in the kernel config but not activated
 321           (it defaults to deactivated on bootup and will only be activated
 322           if some application like powertop activates it explicitly).
 323
 324 config DEBUG_OBJECTS
 325         bool "Debug object operations"
 326         depends on DEBUG_KERNEL
 327         help
 328           If you say Y here, additional code will be inserted into the
 329           kernel to track the life time of various objects and validate
 330           the operations on those objects.
 331
 332 config DEBUG_OBJECTS_SELFTEST
 333         bool "Debug objects selftest"
 334         depends on DEBUG_OBJECTS
 335         help
 336           This enables the selftest of the object debug code.
 337
 338 config DEBUG_OBJECTS_FREE
 339         bool "Debug objects in freed memory"
 340         depends on DEBUG_OBJECTS
 341         help
 342           This enables checks whether a k/v free operation frees an area
 343           which contains an object which has not been deactivated
 344           properly. This can make kmalloc/kfree-intensive workloads
 345           much slower.
 346
 347 config DEBUG_OBJECTS_TIMERS
 348         bool "Debug timer objects"
 349         depends on DEBUG_OBJECTS
 350         help
 351           If you say Y here, additional code will be inserted into the
 352           timer routines to track the life time of timer objects and
 353           validate the timer operations.
 354
 355 config DEBUG_OBJECTS_WORK
 356         bool "Debug work objects"
 357         depends on DEBUG_OBJECTS
 358         help
 359           If you say Y here, additional code will be inserted into the
 360           work queue routines to track the life time of work objects and
 361           validate the work operations.
 362
 363 config DEBUG_OBJECTS_RCU_HEAD
 364         bool "Debug RCU callbacks objects"
 365         depends on DEBUG_OBJECTS
 366         help
 367           Enable this to turn on debugging of RCU list heads (call_rcu() usage).
 368
 369 config DEBUG_OBJECTS_PERCPU_COUNTER
 370         bool "Debug percpu counter objects"
 371         depends on DEBUG_OBJECTS
 372         help
 373           If you say Y here, additional code will be inserted into the
 374           percpu counter routines to track the life time of percpu counter
 375           objects and validate the percpu counter operations.
 376
 377 config DEBUG_OBJECTS_ENABLE_DEFAULT
 378         int "debug_objects bootup default value (0-1)"
 379         range 0 1
 380         default "1"
 381         depends on DEBUG_OBJECTS
 382         help
 383           Debug objects boot parameter default value
 384
 385 config DEBUG_SLAB
 386         bool "Debug slab memory allocations"
 387         depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
 388         help
 389           Say Y here to have the kernel do limited verification on memory
 390           allocation as well as poisoning memory on free to catch use of freed
 391           memory. This can make kmalloc/kfree-intensive workloads much slower.
 392
 393 config DEBUG_SLAB_LEAK
 394         bool "Memory leak debugging"
 395         depends on DEBUG_SLAB
 396
 397 config SLUB_DEBUG_ON
 398         bool "SLUB debugging on by default"
 399         depends on SLUB && SLUB_DEBUG && !KMEMCHECK
 400         default n
 401         help
 402           Boot with debugging on by default. SLUB boots by default with
 403           the runtime debug capabilities switched off. Enabling this is
 404           equivalent to specifying the "slub_debug" parameter on boot.
 405           There is no support for more fine grained debug control like
 406           possible with slub_debug=xxx. SLUB debugging may be switched
 407           off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
 408           "slub_debug=-".
 409
 410 config SLUB_STATS
 411         default n
 412         bool "Enable SLUB performance statistics"
 413         depends on SLUB && SYSFS
 414         help
 415           SLUB statistics are useful to debug SLUBs allocation behavior in
 416           order find ways to optimize the allocator. This should never be
 417           enabled for production use since keeping statistics slows down
 418           the allocator by a few percentage points. The slabinfo command
 419           supports the determination of the most active slabs to figure
 420           out which slabs are relevant to a particular load.
 421           Try running: slabinfo -DA
 422
 423 config DEBUG_KMEMLEAK
 424         bool "Kernel memory leak detector"
 425         depends on DEBUG_KERNEL && EXPERIMENTAL && \
 426                 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
 427
 428         select DEBUG_FS
 429         select STACKTRACE if STACKTRACE_SUPPORT
 430         select KALLSYMS
 431         select CRC32
 432         help
 433           Say Y here if you want to enable the memory leak
 434           detector. The memory allocation/freeing is traced in a way
 435           similar to the Boehm's conservative garbage collector, the
 436           difference being that the orphan objects are not freed but
 437           only shown in /sys/kernel/debug/kmemleak. Enabling this
 438           feature will introduce an overhead to memory
 439           allocations. See Documentation/kmemleak.txt for more
 440           details.
 441
 442           Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
 443           of finding leaks due to the slab objects poisoning.
 444
 445           In order to access the kmemleak file, debugfs needs to be
 446           mounted (usually at /sys/kernel/debug).
 447
 448 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 449         int "Maximum kmemleak early log entries"
 450         depends on DEBUG_KMEMLEAK
 451         range 200 40000
 452         default 400
 453         help
 454           Kmemleak must track all the memory allocations to avoid
 455           reporting false positives. Since memory may be allocated or
 456           freed before kmemleak is initialised, an early log buffer is
 457           used to store these actions. If kmemleak reports "early log
 458           buffer exceeded", please increase this value.
 459
 460 config DEBUG_KMEMLEAK_TEST
 461         tristate "Simple test for the kernel memory leak detector"
 462         depends on DEBUG_KMEMLEAK && m
 463         help
 464           This option enables a module that explicitly leaks memory.
 465
 466           If unsure, say N.
 467
 468 config DEBUG_KMEMLEAK_DEFAULT_OFF
 469         bool "Default kmemleak to off"
 470         depends on DEBUG_KMEMLEAK
 471         help
 472           Say Y here to disable kmemleak by default. It can then be enabled
 473           on the command line via kmemleak=on.
 474
 475 config DEBUG_PREEMPT
 476         bool "Debug preemptible kernel"
 477         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
 478         default y
 479         help
 480           If you say Y here then the kernel will use a debug variant of the
 481           commonly used smp_processor_id() function and will print warnings
 482           if kernel code uses it in a preemption-unsafe way. Also, the kernel
 483           will detect preemption count underflows.
 484
 485 config DEBUG_RT_MUTEXES
 486         bool "RT Mutex debugging, deadlock detection"
 487         depends on DEBUG_KERNEL && RT_MUTEXES
 488         help
 489          This allows rt mutex semantics violations and rt mutex related
 490          deadlocks (lockups) to be detected and reported automatically.
 491
 492 config DEBUG_PI_LIST
 493         bool
 494         default y
 495         depends on DEBUG_RT_MUTEXES
 496
 497 config RT_MUTEX_TESTER
 498         bool "Built-in scriptable tester for rt-mutexes"
 499         depends on DEBUG_KERNEL && RT_MUTEXES
 500         help
 501           This option enables a rt-mutex tester.
 502
 503 config DEBUG_SPINLOCK
 504         bool "Spinlock and rw-lock debugging: basic checks"
 505         depends on DEBUG_KERNEL
 506         select UNINLINE_SPIN_UNLOCK
 507         help
 508           Say Y here and build SMP to catch missing spinlock initialization
 509           and certain other kinds of spinlock errors commonly made.  This is
 510           best used in conjunction with the NMI watchdog so that spinlock
 511           deadlocks are also debuggable.
 512
 513 config DEBUG_MUTEXES
 514         bool "Mutex debugging: basic checks"
 515         depends on DEBUG_KERNEL
 516         help
 517          This feature allows mutex semantics violations to be detected and
 518          reported.
 519
 520 config DEBUG_LOCK_ALLOC
 521         bool "Lock debugging: detect incorrect freeing of live locks"
 522         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 523         select DEBUG_SPINLOCK
 524         select DEBUG_MUTEXES
 525         select LOCKDEP
 526         help
 527          This feature will check whether any held lock (spinlock, rwlock,
 528          mutex or rwsem) is incorrectly freed by the kernel, via any of the
 529          memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
 530          vfree(), etc.), whether a live lock is incorrectly reinitialized via
 531          spin_lock_init()/mutex_init()/etc., or whether there is any lock
 532          held during task exit.
 533
 534 config PROVE_LOCKING
 535         bool "Lock debugging: prove locking correctness"
 536         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 537         select LOCKDEP
 538         select DEBUG_SPINLOCK
 539         select DEBUG_MUTEXES
 540         select DEBUG_LOCK_ALLOC
 541         select TRACE_IRQFLAGS
 542         default n
 543         help
 544          This feature enables the kernel to prove that all locking
 545          that occurs in the kernel runtime is mathematically
 546          correct: that under no circumstance could an arbitrary (and
 547          not yet triggered) combination of observed locking
 548          sequences (on an arbitrary number of CPUs, running an
 549          arbitrary number of tasks and interrupt contexts) cause a
 550          deadlock.
 551
 552          In short, this feature enables the kernel to report locking
 553          related deadlocks before they actually occur.
 554
 555          The proof does not depend on how hard and complex a
 556          deadlock scenario would be to trigger: how many
 557          participant CPUs, tasks and irq-contexts would be needed
 558          for it to trigger. The proof also does not depend on
 559          timing: if a race and a resulting deadlock is possible
 560          theoretically (no matter how unlikely the race scenario
 561          is), it will be proven so and will immediately be
 562          reported by the kernel (once the event is observed that
 563          makes the deadlock theoretically possible).
 564
 565          If a deadlock is impossible (i.e. the locking rules, as
 566          observed by the kernel, are mathematically correct), the
 567          kernel reports nothing.
 568
 569          NOTE: this feature can also be enabled for rwlocks, mutexes
 570          and rwsems - in which case all dependencies between these
 571          different locking variants are observed and mapped too, and
 572          the proof of observed correctness is also maintained for an
 573          arbitrary combination of these separate locking variants.
 574
 575          For more details, see Documentation/lockdep-design.txt.
 576
 577 config PROVE_RCU
 578         bool "RCU debugging: prove RCU correctness"
 579         depends on PROVE_LOCKING
 580         default n
 581         help
 582          This feature enables lockdep extensions that check for correct
 583          use of RCU APIs.  This is currently under development.  Say Y
 584          if you want to debug RCU usage or help work on the PROVE_RCU
 585          feature.
 586
 587          Say N if you are unsure.
 588
 589 config PROVE_RCU_REPEATEDLY
 590         bool "RCU debugging: don't disable PROVE_RCU on first splat"
 591         depends on PROVE_RCU
 592         default n
 593         help
 594          By itself, PROVE_RCU will disable checking upon issuing the
 595          first warning (or "splat").  This feature prevents such
 596          disabling, allowing multiple RCU-lockdep warnings to be printed
 597          on a single reboot.
 598
 599          Say Y to allow multiple RCU-lockdep warnings per boot.
 600
 601          Say N if you are unsure.
 602
 603 config SPARSE_RCU_POINTER
 604         bool "RCU debugging: sparse-based checks for pointer usage"
 605         default n
 606         help
 607          This feature enables the __rcu sparse annotation for
 608          RCU-protected pointers.  This annotation will cause sparse
 609          to flag any non-RCU used of annotated pointers.  This can be
 610          helpful when debugging RCU usage.  Please note that this feature
 611          is not intended to enforce code cleanliness; it is instead merely
 612          a debugging aid.
 613
 614          Say Y to make sparse flag questionable use of RCU-protected pointers
 615
 616          Say N if you are unsure.
 617
 618 config LOCKDEP
 619         bool
 620         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 621         select STACKTRACE
 622         select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
 623         select KALLSYMS
 624         select KALLSYMS_ALL
 625
 626 config LOCK_STAT
 627         bool "Lock usage statistics"
 628         depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
 629         select LOCKDEP
 630         select DEBUG_SPINLOCK
 631         select DEBUG_MUTEXES
 632         select DEBUG_LOCK_ALLOC
 633         default n
 634         help
 635          This feature enables tracking lock contention points
 636
 637          For more details, see Documentation/lockstat.txt
 638
 639          This also enables lock events required by "perf lock",
 640          subcommand of perf.
 641          If you want to use "perf lock", you also need to turn on
 642          CONFIG_EVENT_TRACING.
 643
 644          CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
 645          (CONFIG_LOCKDEP defines "acquire" and "release" events.)
 646
 647 config DEBUG_LOCKDEP
 648         bool "Lock dependency engine debugging"
 649         depends on DEBUG_KERNEL && LOCKDEP
 650         help
 651           If you say Y here, the lock dependency engine will do
 652           additional runtime checks to debug itself, at the price
 653           of more runtime overhead.
 654
 655 config TRACE_IRQFLAGS
 656         bool
 657         help
 658           Enables hooks to interrupt enabling and disabling for
 659           either tracing or lock debugging.
 660
 661 config DEBUG_ATOMIC_SLEEP
 662         bool "Sleep inside atomic section checking"
 663         select PREEMPT_COUNT
 664         depends on DEBUG_KERNEL
 665         help
 666           If you say Y here, various routines which may sleep will become very
 667           noisy if they are called inside atomic sections: when a spinlock is
 668           held, inside an rcu read side critical section, inside preempt disabled
 669           sections, inside an interrupt, etc...
 670
 671 config DEBUG_LOCKING_API_SELFTESTS
 672         bool "Locking API boot-time self-tests"
 673         depends on DEBUG_KERNEL
 674         help
 675           Say Y here if you want the kernel to run a short self-test during
 676           bootup. The self-test checks whether common types of locking bugs
 677           are detected by debugging mechanisms or not. (if you disable
 678           lock debugging then those bugs wont be detected of course.)
 679           The following locking APIs are covered: spinlocks, rwlocks,
 680           mutexes and rwsems.
 681
 682 config STACKTRACE
 683         bool
 684         depends on STACKTRACE_SUPPORT
 685
 686 config DEBUG_STACK_USAGE
 687         bool "Stack utilization instrumentation"
 688         depends on DEBUG_KERNEL
 689         help
 690           Enables the display of the minimum amount of free stack which each
 691           task has ever had available in the sysrq-T and sysrq-P debug output.
 692
 693           This option will slow down process creation somewhat.
 694
 695 config DEBUG_KOBJECT
 696         bool "kobject debugging"
 697         depends on DEBUG_KERNEL
 698         help
 699           If you say Y here, some extra kobject debugging messages will be sent
 700           to the syslog.
 701
 702 config DEBUG_HIGHMEM
 703         bool "Highmem debugging"
 704         depends on DEBUG_KERNEL && HIGHMEM
 705         help
 706           This options enables addition error checking for high memory systems.
 707           Disable for production systems.
 708
 709 config DEBUG_BUGVERBOSE
 710         bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
 711         depends on BUG
 712         depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
 713                    FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE
 714         default y
 715         help
 716           Say Y here to make BUG() panics output the file name and line number
 717           of the BUG call as well as the EIP and oops trace.  This aids
 718           debugging but costs about 70-100K of memory.
 719
 720 config DEBUG_INFO
 721         bool "Compile the kernel with debug info"
 722         depends on DEBUG_KERNEL
 723         help
 724           If you say Y here the resulting kernel image will include
 725           debugging info resulting in a larger kernel image.
 726           This adds debug symbols to the kernel and modules (gcc -g), and
 727           is needed if you intend to use kernel crashdump or binary object
 728           tools like crash, kgdb, LKCD, gdb, etc on the kernel.
 729           Say Y here only if you plan to debug the kernel.
 730
 731           If unsure, say N.
 732
 733 config DEBUG_INFO_REDUCED
 734         bool "Reduce debugging information"
 735         depends on DEBUG_INFO
 736         help
 737           If you say Y here gcc is instructed to generate less debugging
 738           information for structure types. This means that tools that
 739           need full debugging information (like kgdb or systemtap) won't
 740           be happy. But if you merely need debugging information to
 741           resolve line numbers there is no loss. Advantage is that
 742           build directory object sizes shrink dramatically over a full
 743           DEBUG_INFO build and compile times are reduced too.
 744           Only works with newer gcc versions.
 745
 746 config DEBUG_VM
 747         bool "Debug VM"
 748         depends on DEBUG_KERNEL
 749         help
 750           Enable this to turn on extended checks in the virtual-memory system
 751           that may impact performance.
 752
 753           If unsure, say N.
 754
 755 config DEBUG_VIRTUAL
 756         bool "Debug VM translations"
 757         depends on DEBUG_KERNEL && X86
 758         help
 759           Enable some costly sanity checks in virtual to page code. This can
 760           catch mistakes with virt_to_page() and friends.
 761
 762           If unsure, say N.
 763
 764 config DEBUG_NOMMU_REGIONS
 765         bool "Debug the global anon/private NOMMU mapping region tree"
 766         depends on DEBUG_KERNEL && !MMU
 767         help
 768           This option causes the global tree of anonymous and private mapping
 769           regions to be regularly checked for invalid topology.
 770
 771 config DEBUG_WRITECOUNT
 772         bool "Debug filesystem writers count"
 773         depends on DEBUG_KERNEL
 774         help
 775           Enable this to catch wrong use of the writers count in struct
 776           vfsmount.  This will increase the size of each file struct by
 777           32 bits.
 778
 779           If unsure, say N.
 780
 781 config DEBUG_MEMORY_INIT
 782         bool "Debug memory initialisation" if EXPERT
 783         default !EXPERT
 784         help
 785           Enable this for additional checks during memory initialisation.
 786           The sanity checks verify aspects of the VM such as the memory model
 787           and other information provided by the architecture. Verbose
 788           information will be printed at KERN_DEBUG loglevel depending
 789           on the mminit_loglevel= command-line option.
 790
 791           If unsure, say Y
 792
 793 config DEBUG_LIST
 794         bool "Debug linked list manipulation"
 795         depends on DEBUG_KERNEL
 796         help
 797           Enable this to turn on extended checks in the linked-list
 798           walking routines.
 799
 800           If unsure, say N.
 801
 802 config TEST_LIST_SORT
 803         bool "Linked list sorting test"
 804         depends on DEBUG_KERNEL
 805         help
 806           Enable this to turn on 'list_sort()' function test. This test is
 807           executed only once during system boot, so affects only boot time.
 808
 809           If unsure, say N.
 810
 811 config DEBUG_SG
 812         bool "Debug SG table operations"
 813         depends on DEBUG_KERNEL
 814         help
 815           Enable this to turn on checks on scatter-gather tables. This can
 816           help find problems with drivers that do not properly initialize
 817           their sg tables.
 818
 819           If unsure, say N.
 820
 821 config DEBUG_NOTIFIERS
 822         bool "Debug notifier call chains"
 823         depends on DEBUG_KERNEL
 824         help
 825           Enable this to turn on sanity checking for notifier call chains.
 826           This is most useful for kernel developers to make sure that
 827           modules properly unregister themselves from notifier chains.
 828           This is a relatively cheap check but if you care about maximum
 829           performance, say N.
 830
 831 config DEBUG_CREDENTIALS
 832         bool "Debug credential management"
 833         depends on DEBUG_KERNEL
 834         help
 835           Enable this to turn on some debug checking for credential
 836           management.  The additional code keeps track of the number of
 837           pointers from task_structs to any given cred struct, and checks to
 838           see that this number never exceeds the usage count of the cred
 839           struct.
 840
 841           Furthermore, if SELinux is enabled, this also checks that the
 842           security pointer in the cred struct is never seen to be invalid.
 843
 844           If unsure, say N.
 845
 846 #
 847 # Select this config option from the architecture Kconfig, if it
 848 # is preferred to always offer frame pointers as a config
 849 # option on the architecture (regardless of KERNEL_DEBUG):
 850 #
 851 config ARCH_WANT_FRAME_POINTERS
 852         bool
 853         help
 854
 855 config FRAME_POINTER
 856         bool "Compile the kernel with frame pointers"
 857         depends on DEBUG_KERNEL && \
 858                 (CRIS || M68K || FRV || UML || \
 859                  AVR32 || SUPERH || BLACKFIN || MN10300) || \
 860                 ARCH_WANT_FRAME_POINTERS
 861         default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 862         help
 863           If you say Y here the resulting kernel image will be slightly
 864           larger and slower, but it gives very useful debugging information
 865           in case of kernel bugs. (precise oopses/stacktraces/warnings)
 866
 867 config BOOT_PRINTK_DELAY
 868         bool "Delay each boot printk message by N milliseconds"
 869         depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
 870         help
 871           This build option allows you to read kernel boot messages
 872           by inserting a short delay after each one.  The delay is
 873           specified in milliseconds on the kernel command line,
 874           using "boot_delay=N".
 875
 876           It is likely that you would also need to use "lpj=M" to preset
 877           the "loops per jiffie" value.
 878           See a previous boot log for the "lpj" value to use for your
 879           system, and then set "lpj=M" before setting "boot_delay=N".
 880           NOTE:  Using this option may adversely affect SMP systems.
 881           I.e., processors other than the first one may not boot up.
 882           BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
 883           what it believes to be lockup conditions.
 884
 885 config RCU_TORTURE_TEST
 886         tristate "torture tests for RCU"
 887         depends on DEBUG_KERNEL
 888         default n
 889         help
 890           This option provides a kernel module that runs torture tests
 891           on the RCU infrastructure.  The kernel module may be built
 892           after the fact on the running kernel to be tested, if desired.
 893
 894           Say Y here if you want RCU torture tests to be built into
 895           the kernel.
 896           Say M if you want the RCU torture tests to build as a module.
 897           Say N if you are unsure.
 898
 899 config RCU_TORTURE_TEST_RUNNABLE
 900         bool "torture tests for RCU runnable by default"
 901         depends on RCU_TORTURE_TEST = y
 902         default n
 903         help
 904           This option provides a way to build the RCU torture tests
 905           directly into the kernel without them starting up at boot
 906           time.  You can use /proc/sys/kernel/rcutorture_runnable
 907           to manually override this setting.  This /proc file is
 908           available only when the RCU torture tests have been built
 909           into the kernel.
 910
 911           Say Y here if you want the RCU torture tests to start during
 912           boot (you probably don't).
 913           Say N here if you want the RCU torture tests to start only
 914           after being manually enabled via /proc.
 915
 916 config RCU_CPU_STALL_TIMEOUT
 917         int "RCU CPU stall timeout in seconds"
 918         depends on TREE_RCU || TREE_PREEMPT_RCU
 919         range 3 300
 920         default 60
 921         help
 922           If a given RCU grace period extends more than the specified
 923           number of seconds, a CPU stall warning is printed.  If the
 924           RCU grace period persists, additional CPU stall warnings are
 925           printed at more widely spaced intervals.
 926
 927 config RCU_CPU_STALL_VERBOSE
 928         bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
 929         depends on TREE_PREEMPT_RCU
 930         default y
 931         help
 932           This option causes RCU to printk detailed per-task information
 933           for any tasks that are stalling the current RCU grace period.
 934
 935           Say N if you are unsure.
 936
 937           Say Y if you want to enable such checks.
 938
 939 config RCU_CPU_STALL_INFO
 940         bool "Print additional diagnostics on RCU CPU stall"
 941         depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
 942         default n
 943         help
 944           For each stalled CPU that is aware of the current RCU grace
 945           period, print out additional per-CPU diagnostic information
 946           regarding scheduling-clock ticks, idle state, and,
 947           for RCU_FAST_NO_HZ kernels, idle-entry state.
 948
 949           Say N if you are unsure.
 950
 951           Say Y if you want to enable such diagnostics.
 952
 953 config RCU_TRACE
 954         bool "Enable tracing for RCU"
 955         depends on DEBUG_KERNEL
 956         help
 957           This option provides tracing in RCU which presents stats
 958           in debugfs for debugging RCU implementation.
 959
 960           Say Y here if you want to enable RCU tracing
 961           Say N if you are unsure.
 962
 963 config KPROBES_SANITY_TEST
 964         bool "Kprobes sanity tests"
 965         depends on DEBUG_KERNEL
 966         depends on KPROBES
 967         default n
 968         help
 969           This option provides for testing basic kprobes functionality on
 970           boot. A sample kprobe, jprobe and kretprobe are inserted and
 971           verified for functionality.
 972
 973           Say N if you are unsure.
 974
 975 config BACKTRACE_SELF_TEST
 976         tristate "Self test for the backtrace code"
 977         depends on DEBUG_KERNEL
 978         default n
 979         help
 980           This option provides a kernel module that can be used to test
 981           the kernel stack backtrace code. This option is not useful
 982           for distributions or general kernels, but only for kernel
 983           developers working on architecture code.
 984
 985           Note that if you want to also test saved backtraces, you will
 986           have to enable STACKTRACE as well.
 987
 988           Say N if you are unsure.
 989
 990 config DEBUG_BLOCK_EXT_DEVT
 991         bool "Force extended block device numbers and spread them"
 992         depends on DEBUG_KERNEL
 993         depends on BLOCK
 994         default n
 995         help
 996           BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
 997           SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
 998           YOU ARE DOING.  Distros, please enable this and fix whatever
 999           is broken.
1000
1001           Conventionally, block device numbers are allocated from
1002           predetermined contiguous area.  However, extended block area
1003           may introduce non-contiguous block device numbers.  This
1004           option forces most block device numbers to be allocated from
1005           the extended space and spreads them to discover kernel or
1006           userland code paths which assume predetermined contiguous
1007           device number allocation.
1008
1009           Note that turning on this debug option shuffles all the
1010           device numbers for all IDE and SCSI devices including libata
1011           ones, so root partition specified using device number
1012           directly (via rdev or root=MAJ:MIN) won't work anymore.
1013           Textual device names (root=/dev/sdXn) will continue to work.
1014
1015           Say N if you are unsure.
1016
1017 config DEBUG_FORCE_WEAK_PER_CPU
1018         bool "Force weak per-cpu definitions"
1019         depends on DEBUG_KERNEL
1020         help
1021           s390 and alpha require percpu variables in modules to be
1022           defined weak to work around addressing range issue which
1023           puts the following two restrictions on percpu variable
1024           definitions.
1025
1026           1. percpu symbols must be unique whether static or not
1027           2. percpu variables can't be defined inside a function
1028
1029           To ensure that generic code follows the above rules, this
1030           option forces all percpu variables to be defined as weak.
1031
1032 config DEBUG_PER_CPU_MAPS
1033         bool "Debug access to per_cpu maps"
1034         depends on DEBUG_KERNEL
1035         depends on SMP
1036         help
1037           Say Y to verify that the per_cpu map being accessed has
1038           been set up. This adds a fair amount of code to kernel memory
1039           and decreases performance.
1040
1041           Say N if unsure.
1042
1043 config LKDTM
1044         tristate "Linux Kernel Dump Test Tool Module"
1045         depends on DEBUG_FS
1046         depends on BLOCK
1047         default n
1048         help
1049         This module enables testing of the different dumping mechanisms by
1050         inducing system failures at predefined crash points.
1051         If you don't need it: say N
1052         Choose M here to compile this code as a module. The module will be
1053         called lkdtm.
1054
1055         Documentation on how to use the module can be found in
1056         Documentation/fault-injection/provoke-crashes.txt
1057
1058 config CPU_NOTIFIER_ERROR_INJECT
1059         tristate "CPU notifier error injection module"
1060         depends on HOTPLUG_CPU && DEBUG_KERNEL
1061         help
1062           This option provides a kernel module that can be used to test
1063           the error handling of the cpu notifiers
1064
1065           To compile this code as a module, choose M here: the module will
1066           be called cpu-notifier-error-inject.
1067
1068           If unsure, say N.
1069
1070 config FAULT_INJECTION
1071         bool "Fault-injection framework"
1072         depends on DEBUG_KERNEL
1073         help
1074           Provide fault-injection framework.
1075           For more details, see Documentation/fault-injection/.
1076
1077 config FAILSLAB
1078         bool "Fault-injection capability for kmalloc"
1079         depends on FAULT_INJECTION
1080         depends on SLAB || SLUB
1081         help
1082           Provide fault-injection capability for kmalloc.
1083
1084 config FAIL_PAGE_ALLOC
1085         bool "Fault-injection capabilitiy for alloc_pages()"
1086         depends on FAULT_INJECTION
1087         help
1088           Provide fault-injection capability for alloc_pages().
1089
1090 config FAIL_MAKE_REQUEST
1091         bool "Fault-injection capability for disk IO"
1092         depends on FAULT_INJECTION && BLOCK
1093         help
1094           Provide fault-injection capability for disk IO.
1095
1096 config FAIL_IO_TIMEOUT
1097         bool "Fault-injection capability for faking disk interrupts"
1098         depends on FAULT_INJECTION && BLOCK
1099         help
1100           Provide fault-injection capability on end IO handling. This
1101           will make the block layer "forget" an interrupt as configured,
1102           thus exercising the error handling.
1103
1104           Only works with drivers that use the generic timeout handling,
1105           for others it wont do anything.
1106
1107 config FAIL_MMC_REQUEST
1108         bool "Fault-injection capability for MMC IO"
1109         select DEBUG_FS
1110         depends on FAULT_INJECTION && MMC
1111         help
1112           Provide fault-injection capability for MMC IO.
1113           This will make the mmc core return data errors. This is
1114           useful to test the error handling in the mmc block device
1115           and to test how the mmc host driver handles retries from
1116           the block device.
1117
1118 config FAULT_INJECTION_DEBUG_FS
1119         bool "Debugfs entries for fault-injection capabilities"
1120         depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1121         help
1122           Enable configuration of fault-injection capabilities via debugfs.
1123
1124 config FAULT_INJECTION_STACKTRACE_FILTER
1125         bool "stacktrace filter for fault-injection capabilities"
1126         depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1127         depends on !X86_64
1128         select STACKTRACE
1129         select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1130         help
1131           Provide stacktrace filter for fault-injection capabilities
1132
1133 config LATENCYTOP
1134         bool "Latency measuring infrastructure"
1135         depends on HAVE_LATENCYTOP_SUPPORT
1136         depends on DEBUG_KERNEL
1137         depends on STACKTRACE_SUPPORT
1138         depends on PROC_FS
1139         select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1140         select KALLSYMS
1141         select KALLSYMS_ALL
1142         select STACKTRACE
1143         select SCHEDSTATS
1144         select SCHED_DEBUG
1145         help
1146           Enable this option if you want to use the LatencyTOP tool
1147           to find out which userspace is blocking on what kernel operations.
1148
1149 source mm/Kconfig.debug
1150 source kernel/trace/Kconfig
1151
1152 config PROVIDE_OHCI1394_DMA_INIT
1153         bool "Remote debugging over FireWire early on boot"
1154         depends on PCI && X86
1155         help
1156           If you want to debug problems which hang or crash the kernel early
1157           on boot and the crashing machine has a FireWire port, you can use
1158           this feature to remotely access the memory of the crashed machine
1159           over FireWire. This employs remote DMA as part of the OHCI1394
1160           specification which is now the standard for FireWire controllers.
1161
1162           With remote DMA, you can monitor the printk buffer remotely using
1163           firescope and access all memory below 4GB using fireproxy from gdb.
1164           Even controlling a kernel debugger is possible using remote DMA.
1165
1166           Usage:
1167
1168           If ohci1394_dma=early is used as boot parameter, it will initialize
1169           all OHCI1394 controllers which are found in the PCI config space.
1170
1171           As all changes to the FireWire bus such as enabling and disabling
1172           devices cause a bus reset and thereby disable remote DMA for all
1173           devices, be sure to have the cable plugged and FireWire enabled on
1174           the debugging host before booting the debug target for debugging.
1175
1176           This code (~1k) is freed after boot. By then, the firewire stack
1177           in charge of the OHCI-1394 controllers should be used instead.
1178
1179           See Documentation/debugging-via-ohci1394.txt for more information.
1180
1181 config FIREWIRE_OHCI_REMOTE_DMA
1182         bool "Remote debugging over FireWire with firewire-ohci"
1183         depends on FIREWIRE_OHCI
1184         help
1185           This option lets you use the FireWire bus for remote debugging
1186           with help of the firewire-ohci driver. It enables unfiltered
1187           remote DMA in firewire-ohci.
1188           See Documentation/debugging-via-ohci1394.txt for more information.
1189
1190           If unsure, say N.
1191
1192 config BUILD_DOCSRC
1193         bool "Build targets in Documentation/ tree"
1194         depends on HEADERS_CHECK
1195         help
1196           This option attempts to build objects from the source files in the
1197           kernel Documentation/ tree.
1198
1199           Say N if you are unsure.
1200
1201 config DYNAMIC_DEBUG
1202         bool "Enable dynamic printk() support"
1203         default n
1204         depends on PRINTK
1205         depends on DEBUG_FS
1206         help
1207
1208           Compiles debug level messages into the kernel, which would not
1209           otherwise be available at runtime. These messages can then be
1210           enabled/disabled based on various levels of scope - per source file,
1211           function, module, format string, and line number. This mechanism
1212           implicitly compiles in all pr_debug() and dev_dbg() calls, which
1213           enlarges the kernel text size by about 2%.
1214
1215           If a source file is compiled with DEBUG flag set, any
1216           pr_debug() calls in it are enabled by default, but can be
1217           disabled at runtime as below.  Note that DEBUG flag is
1218           turned on by many CONFIG_*DEBUG* options.
1219
1220           Usage:
1221
1222           Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1223           which is contained in the 'debugfs' filesystem. Thus, the debugfs
1224           filesystem must first be mounted before making use of this feature.
1225           We refer the control file as: <debugfs>/dynamic_debug/control. This
1226           file contains a list of the debug statements that can be enabled. The
1227           format for each line of the file is:
1228
1229                 filename:lineno [module]function flags format
1230
1231           filename : source file of the debug statement
1232           lineno : line number of the debug statement
1233           module : module that contains the debug statement
1234           function : function that contains the debug statement
1235           flags : '=p' means the line is turned 'on' for printing
1236           format : the format used for the debug statement
1237
1238           From a live system:
1239
1240                 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1241                 # filename:lineno [module]function flags format
1242                 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
1243                 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
1244                 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
1245
1246           Example usage:
1247
1248                 // enable the message at line 1603 of file svcsock.c
1249                 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1250                                                 <debugfs>/dynamic_debug/control
1251
1252                 // enable all the messages in file svcsock.c
1253                 nullarbor:~ # echo -n 'file svcsock.c +p' >
1254                                                 <debugfs>/dynamic_debug/control
1255
1256                 // enable all the messages in the NFS server module
1257                 nullarbor:~ # echo -n 'module nfsd +p' >
1258                                                 <debugfs>/dynamic_debug/control
1259
1260                 // enable all 12 messages in the function svc_process()
1261                 nullarbor:~ # echo -n 'func svc_process +p' >
1262                                                 <debugfs>/dynamic_debug/control
1263
1264                 // disable all 12 messages in the function svc_process()
1265                 nullarbor:~ # echo -n 'func svc_process -p' >
1266                                                 <debugfs>/dynamic_debug/control
1267
1268           See Documentation/dynamic-debug-howto.txt for additional information.
1269
1270 config DMA_API_DEBUG
1271         bool "Enable debugging of DMA-API usage"
1272         depends on HAVE_DMA_API_DEBUG
1273         help
1274           Enable this option to debug the use of the DMA API by device drivers.
1275           With this option you will be able to detect common bugs in device
1276           drivers like double-freeing of DMA mappings or freeing mappings that
1277           were never allocated.
1278           This option causes a performance degredation.  Use only if you want
1279           to debug device drivers. If unsure, say N.
1280
1281 config ATOMIC64_SELFTEST
1282         bool "Perform an atomic64_t self-test at boot"
1283         help
1284           Enable this option to test the atomic64_t functions at boot.
1285
1286           If unsure, say N.
1287
1288 config ASYNC_RAID6_TEST
1289         tristate "Self test for hardware accelerated raid6 recovery"
1290         depends on ASYNC_RAID6_RECOV
1291         select ASYNC_MEMCPY
1292         ---help---
1293           This is a one-shot self test that permutes through the
1294           recovery of all the possible two disk failure scenarios for a
1295           N-disk array.  Recovery is performed with the asynchronous
1296           raid6 recovery routines, and will optionally use an offload
1297           engine if one is available.
1298
1299           If unsure, say N.
1300
1301 source "samples/Kconfig"
1302
1303 source "lib/Kconfig.kgdb"
1304
1305 source "lib/Kconfig.kmemcheck"
1306
1307 config TEST_KSTRTOX
1308         tristate "Test kstrto*() family of functions at runtime"