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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.
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.
14 The behavior is also controlled by the kernel command line
15 parameter printk.time=1. See Documentation/kernel-parameters.txt
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.
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.
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.
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.
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
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.
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.
77 config READABLE_ASM
78 bool "Generate readable assembler code"
79 depends on DEBUG_KERNEL
80 help
81 Disable some compiler optimizations that tend to generate human unreadable
82 assembler output. This may make the kernel slightly slower, but it helps
83 to keep kernel developers who have to stare a lot at assembler listings
84 sane.
86 config UNUSED_SYMBOLS
87 bool "Enable unused/obsolete exported symbols"
88 default y if X86
89 help
90 Unused but exported symbols make the kernel needlessly bigger. For
91 that reason most of these unused exports will soon be removed. This
92 option is provided temporarily to provide a transition period in case
93 some external kernel module needs one of these symbols anyway. If you
94 encounter such a case in your module, consider if you are actually
95 using the right API. (rationale: since nobody in the kernel is using
96 this in a module, there is a pretty good chance it's actually the
97 wrong interface to use). If you really need the symbol, please send a
98 mail to the linux kernel mailing list mentioning the symbol and why
99 you really need it, and what the merge plan to the mainline kernel for
100 your module is.
102 config DEBUG_FS
103 bool "Debug Filesystem"
104 help
105 debugfs is a virtual file system that kernel developers use to put
106 debugging files into. Enable this option to be able to read and
107 write to these files.
109 For detailed documentation on the debugfs API, see
110 Documentation/DocBook/filesystems.
112 If unsure, say N.
114 config HEADERS_CHECK
115 bool "Run 'make headers_check' when building vmlinux"
116 depends on !UML
117 help
118 This option will extract the user-visible kernel headers whenever
119 building the kernel, and will run basic sanity checks on them to
120 ensure that exported files do not attempt to include files which
121 were not exported, etc.
123 If you're making modifications to header files which are
124 relevant for userspace, say 'Y', and check the headers
125 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
126 your build tree), to make sure they're suitable.
128 config DEBUG_SECTION_MISMATCH
129 bool "Enable full Section mismatch analysis"
130 help
131 The section mismatch analysis checks if there are illegal
132 references from one section to another section.
133 During linktime or runtime, some sections are dropped;
134 any use of code/data previously in these sections would
135 most likely result in an oops.
136 In the code, functions and variables are annotated with
137 __init, __devinit, etc. (see the full list in include/linux/init.h),
138 which results in the code/data being placed in specific sections.
139 The section mismatch analysis is always performed after a full
140 kernel build, and enabling this option causes the following
141 additional steps to occur:
142 - Add the option -fno-inline-functions-called-once to gcc commands.
143 When inlining a function annotated with __init in a non-init
144 function, we would lose the section information and thus
145 the analysis would not catch the illegal reference.
146 This option tells gcc to inline less (but it does result in
147 a larger kernel).
148 - Run the section mismatch analysis for each module/built-in.o file.
149 When we run the section mismatch analysis on vmlinux.o, we
150 lose valueble information about where the mismatch was
151 introduced.
152 Running the analysis for each module/built-in.o file
153 tells where the mismatch happens much closer to the
154 source. The drawback is that the same mismatch is
155 reported at least twice.
156 - Enable verbose reporting from modpost in order to help resolve
157 the section mismatches that are reported.
159 config DEBUG_KERNEL
160 bool "Kernel debugging"
161 help
162 Say Y here if you are developing drivers or trying to debug and
163 identify kernel problems.
165 config DEBUG_SHIRQ
166 bool "Debug shared IRQ handlers"
167 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
168 help
169 Enable this to generate a spurious interrupt as soon as a shared
170 interrupt handler is registered, and just before one is deregistered.
171 Drivers ought to be able to handle interrupts coming in at those
172 points; some don't and need to be caught.
174 config LOCKUP_DETECTOR
175 bool "Detect Hard and Soft Lockups"
176 depends on DEBUG_KERNEL && !S390
177 help
178 Say Y here to enable the kernel to act as a watchdog to detect
179 hard and soft lockups.
181 Softlockups are bugs that cause the kernel to loop in kernel
182 mode for more than 20 seconds, without giving other tasks a
183 chance to run. The current stack trace is displayed upon
184 detection and the system will stay locked up.
186 Hardlockups are bugs that cause the CPU to loop in kernel mode
187 for more than 10 seconds, without letting other interrupts have a
188 chance to run. The current stack trace is displayed upon detection
189 and the system will stay locked up.
191 The overhead should be minimal. A periodic hrtimer runs to
192 generate interrupts and kick the watchdog task every 4 seconds.
193 An NMI is generated every 10 seconds or so to check for hardlockups.
195 The frequency of hrtimer and NMI events and the soft and hard lockup
196 thresholds can be controlled through the sysctl watchdog_thresh.
198 config HARDLOCKUP_DETECTOR
199 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
200 !HAVE_NMI_WATCHDOG
202 config BOOTPARAM_HARDLOCKUP_PANIC
203 bool "Panic (Reboot) On Hard Lockups"
204 depends on LOCKUP_DETECTOR
205 help
206 Say Y here to enable the kernel to panic on "hard lockups",
207 which are bugs that cause the kernel to loop in kernel
208 mode with interrupts disabled for more than 10 seconds (configurable
209 using the watchdog_thresh sysctl).
211 Say N if unsure.
213 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
214 int
215 depends on LOCKUP_DETECTOR
216 range 0 1
217 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
218 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
220 config BOOTPARAM_SOFTLOCKUP_PANIC
221 bool "Panic (Reboot) On Soft Lockups"
222 depends on LOCKUP_DETECTOR
223 help
224 Say Y here to enable the kernel to panic on "soft lockups",
225 which are bugs that cause the kernel to loop in kernel
226 mode for more than 20 seconds (configurable using the watchdog_thresh
227 sysctl), without giving other tasks a chance to run.
229 The panic can be used in combination with panic_timeout,
230 to cause the system to reboot automatically after a
231 lockup has been detected. This feature is useful for
232 high-availability systems that have uptime guarantees and
233 where a lockup must be resolved ASAP.
235 Say N if unsure.
237 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
238 int
239 depends on LOCKUP_DETECTOR
240 range 0 1
241 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
242 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
244 config DETECT_HUNG_TASK
245 bool "Detect Hung Tasks"
246 depends on DEBUG_KERNEL
247 default LOCKUP_DETECTOR
248 help
249 Say Y here to enable the kernel to detect "hung tasks",
250 which are bugs that cause the task to be stuck in
251 uninterruptible "D" state indefinitiley.
253 When a hung task is detected, the kernel will print the
254 current stack trace (which you should report), but the
255 task will stay in uninterruptible state. If lockdep is
256 enabled then all held locks will also be reported. This
257 feature has negligible overhead.
259 config DEFAULT_HUNG_TASK_TIMEOUT
260 int "Default timeout for hung task detection (in seconds)"
261 depends on DETECT_HUNG_TASK
262 default 120
263 help
264 This option controls the default timeout (in seconds) used
265 to determine when a task has become non-responsive and should
266 be considered hung.
268 It can be adjusted at runtime via the kernel.hung_task_timeout_secs
269 sysctl or by writing a value to
270 /proc/sys/kernel/hung_task_timeout_secs.
272 A timeout of 0 disables the check. The default is two minutes.
273 Keeping the default should be fine in most cases.
275 config BOOTPARAM_HUNG_TASK_PANIC
276 bool "Panic (Reboot) On Hung Tasks"
277 depends on DETECT_HUNG_TASK
278 help
279 Say Y here to enable the kernel to panic on "hung tasks",
280 which are bugs that cause the kernel to leave a task stuck
281 in uninterruptible "D" state.
283 The panic can be used in combination with panic_timeout,
284 to cause the system to reboot automatically after a
285 hung task has been detected. This feature is useful for
286 high-availability systems that have uptime guarantees and
287 where a hung tasks must be resolved ASAP.
289 Say N if unsure.
291 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
292 int
293 depends on DETECT_HUNG_TASK
294 range 0 1
295 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
296 default 1 if BOOTPARAM_HUNG_TASK_PANIC
298 config SCHED_DEBUG
299 bool "Collect scheduler debugging info"
300 depends on DEBUG_KERNEL && PROC_FS
301 default y
302 help
303 If you say Y here, the /proc/sched_debug file will be provided
304 that can help debug the scheduler. The runtime overhead of this
305 option is minimal.
307 config SCHEDSTATS
308 bool "Collect scheduler statistics"
309 depends on DEBUG_KERNEL && PROC_FS
310 help
311 If you say Y here, additional code will be inserted into the
312 scheduler and related routines to collect statistics about
313 scheduler behavior and provide them in /proc/schedstat. These
314 stats may be useful for both tuning and debugging the scheduler
315 If you aren't debugging the scheduler or trying to tune a specific
316 application, you can say N to avoid the very slight overhead
317 this adds.
319 config TIMER_STATS
320 bool "Collect kernel timers statistics"
321 depends on DEBUG_KERNEL && PROC_FS
322 help
323 If you say Y here, additional code will be inserted into the
324 timer routines to collect statistics about kernel timers being
325 reprogrammed. The statistics can be read from /proc/timer_stats.
326 The statistics collection is started by writing 1 to /proc/timer_stats,
327 writing 0 stops it. This feature is useful to collect information
328 about timer usage patterns in kernel and userspace. This feature
329 is lightweight if enabled in the kernel config but not activated
330 (it defaults to deactivated on bootup and will only be activated
331 if some application like powertop activates it explicitly).
333 config DEBUG_OBJECTS
334 bool "Debug object operations"
335 depends on DEBUG_KERNEL
336 help
337 If you say Y here, additional code will be inserted into the
338 kernel to track the life time of various objects and validate
339 the operations on those objects.
341 config DEBUG_OBJECTS_SELFTEST
342 bool "Debug objects selftest"
343 depends on DEBUG_OBJECTS
344 help
345 This enables the selftest of the object debug code.
347 config DEBUG_OBJECTS_FREE
348 bool "Debug objects in freed memory"
349 depends on DEBUG_OBJECTS
350 help
351 This enables checks whether a k/v free operation frees an area
352 which contains an object which has not been deactivated
353 properly. This can make kmalloc/kfree-intensive workloads
354 much slower.
356 config DEBUG_OBJECTS_TIMERS
357 bool "Debug timer objects"
358 depends on DEBUG_OBJECTS
359 help
360 If you say Y here, additional code will be inserted into the
361 timer routines to track the life time of timer objects and
362 validate the timer operations.
364 config DEBUG_OBJECTS_WORK
365 bool "Debug work objects"
366 depends on DEBUG_OBJECTS
367 help
368 If you say Y here, additional code will be inserted into the
369 work queue routines to track the life time of work objects and
370 validate the work operations.
372 config DEBUG_OBJECTS_RCU_HEAD
373 bool "Debug RCU callbacks objects"
374 depends on DEBUG_OBJECTS
375 help
376 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
378 config DEBUG_OBJECTS_PERCPU_COUNTER
379 bool "Debug percpu counter objects"
380 depends on DEBUG_OBJECTS
381 help
382 If you say Y here, additional code will be inserted into the
383 percpu counter routines to track the life time of percpu counter
384 objects and validate the percpu counter operations.
386 config DEBUG_OBJECTS_ENABLE_DEFAULT
387 int "debug_objects bootup default value (0-1)"
388 range 0 1
389 default "1"
390 depends on DEBUG_OBJECTS
391 help
392 Debug objects boot parameter default value
394 config DEBUG_SLAB
395 bool "Debug slab memory allocations"
396 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
397 help
398 Say Y here to have the kernel do limited verification on memory
399 allocation as well as poisoning memory on free to catch use of freed
400 memory. This can make kmalloc/kfree-intensive workloads much slower.
402 config DEBUG_SLAB_LEAK
403 bool "Memory leak debugging"
404 depends on DEBUG_SLAB
406 config SLUB_DEBUG_ON
407 bool "SLUB debugging on by default"
408 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
409 default n
410 help
411 Boot with debugging on by default. SLUB boots by default with
412 the runtime debug capabilities switched off. Enabling this is
413 equivalent to specifying the "slub_debug" parameter on boot.
414 There is no support for more fine grained debug control like
415 possible with slub_debug=xxx. SLUB debugging may be switched
416 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
417 "slub_debug=-".
419 config SLUB_STATS
420 default n
421 bool "Enable SLUB performance statistics"
422 depends on SLUB && SYSFS
423 help
424 SLUB statistics are useful to debug SLUBs allocation behavior in
425 order find ways to optimize the allocator. This should never be
426 enabled for production use since keeping statistics slows down
427 the allocator by a few percentage points. The slabinfo command
428 supports the determination of the most active slabs to figure
429 out which slabs are relevant to a particular load.
430 Try running: slabinfo -DA
432 config DEBUG_KMEMLEAK
433 bool "Kernel memory leak detector"
434 depends on DEBUG_KERNEL && EXPERIMENTAL && \
435 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
437 select DEBUG_FS
438 select STACKTRACE if STACKTRACE_SUPPORT
439 select KALLSYMS
440 select CRC32
441 help
442 Say Y here if you want to enable the memory leak
443 detector. The memory allocation/freeing is traced in a way
444 similar to the Boehm's conservative garbage collector, the
445 difference being that the orphan objects are not freed but
446 only shown in /sys/kernel/debug/kmemleak. Enabling this
447 feature will introduce an overhead to memory
448 allocations. See Documentation/kmemleak.txt for more
449 details.
451 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
452 of finding leaks due to the slab objects poisoning.
454 In order to access the kmemleak file, debugfs needs to be
455 mounted (usually at /sys/kernel/debug).
457 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
458 int "Maximum kmemleak early log entries"
459 depends on DEBUG_KMEMLEAK
460 range 200 40000
461 default 400
462 help
463 Kmemleak must track all the memory allocations to avoid
464 reporting false positives. Since memory may be allocated or
465 freed before kmemleak is initialised, an early log buffer is
466 used to store these actions. If kmemleak reports "early log
467 buffer exceeded", please increase this value.
469 config DEBUG_KMEMLEAK_TEST
470 tristate "Simple test for the kernel memory leak detector"
471 depends on DEBUG_KMEMLEAK && m
472 help
473 This option enables a module that explicitly leaks memory.
475 If unsure, say N.
477 config DEBUG_KMEMLEAK_DEFAULT_OFF
478 bool "Default kmemleak to off"
479 depends on DEBUG_KMEMLEAK
480 help
481 Say Y here to disable kmemleak by default. It can then be enabled
482 on the command line via kmemleak=on.
484 config DEBUG_PREEMPT
485 bool "Debug preemptible kernel"
486 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
487 default y
488 help
489 If you say Y here then the kernel will use a debug variant of the
490 commonly used smp_processor_id() function and will print warnings
491 if kernel code uses it in a preemption-unsafe way. Also, the kernel
492 will detect preemption count underflows.
494 config DEBUG_RT_MUTEXES
495 bool "RT Mutex debugging, deadlock detection"
496 depends on DEBUG_KERNEL && RT_MUTEXES
497 help
498 This allows rt mutex semantics violations and rt mutex related
499 deadlocks (lockups) to be detected and reported automatically.
501 config DEBUG_PI_LIST
502 bool
503 default y
504 depends on DEBUG_RT_MUTEXES
506 config RT_MUTEX_TESTER
507 bool "Built-in scriptable tester for rt-mutexes"
508 depends on DEBUG_KERNEL && RT_MUTEXES
509 help
510 This option enables a rt-mutex tester.
512 config DEBUG_SPINLOCK
513 bool "Spinlock and rw-lock debugging: basic checks"
514 depends on DEBUG_KERNEL
515 select UNINLINE_SPIN_UNLOCK
516 help
517 Say Y here and build SMP to catch missing spinlock initialization
518 and certain other kinds of spinlock errors commonly made. This is
519 best used in conjunction with the NMI watchdog so that spinlock
520 deadlocks are also debuggable.
522 config DEBUG_MUTEXES
523 bool "Mutex debugging: basic checks"
524 depends on DEBUG_KERNEL
525 help
526 This feature allows mutex semantics violations to be detected and
527 reported.
529 config DEBUG_LOCK_ALLOC
530 bool "Lock debugging: detect incorrect freeing of live locks"
531 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
532 select DEBUG_SPINLOCK
533 select DEBUG_MUTEXES
534 select LOCKDEP
535 help
536 This feature will check whether any held lock (spinlock, rwlock,
537 mutex or rwsem) is incorrectly freed by the kernel, via any of the
538 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
539 vfree(), etc.), whether a live lock is incorrectly reinitialized via
540 spin_lock_init()/mutex_init()/etc., or whether there is any lock
541 held during task exit.
543 config PROVE_LOCKING
544 bool "Lock debugging: prove locking correctness"
545 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
546 select LOCKDEP
547 select DEBUG_SPINLOCK
548 select DEBUG_MUTEXES
549 select DEBUG_LOCK_ALLOC
550 select TRACE_IRQFLAGS
551 default n
552 help
553 This feature enables the kernel to prove that all locking
554 that occurs in the kernel runtime is mathematically
555 correct: that under no circumstance could an arbitrary (and
556 not yet triggered) combination of observed locking
557 sequences (on an arbitrary number of CPUs, running an
558 arbitrary number of tasks and interrupt contexts) cause a
559 deadlock.
561 In short, this feature enables the kernel to report locking
562 related deadlocks before they actually occur.
564 The proof does not depend on how hard and complex a
565 deadlock scenario would be to trigger: how many
566 participant CPUs, tasks and irq-contexts would be needed
567 for it to trigger. The proof also does not depend on
568 timing: if a race and a resulting deadlock is possible
569 theoretically (no matter how unlikely the race scenario
570 is), it will be proven so and will immediately be
571 reported by the kernel (once the event is observed that
572 makes the deadlock theoretically possible).
574 If a deadlock is impossible (i.e. the locking rules, as
575 observed by the kernel, are mathematically correct), the
576 kernel reports nothing.
578 NOTE: this feature can also be enabled for rwlocks, mutexes
579 and rwsems - in which case all dependencies between these
580 different locking variants are observed and mapped too, and
581 the proof of observed correctness is also maintained for an
582 arbitrary combination of these separate locking variants.
584 For more details, see Documentation/lockdep-design.txt.
586 config PROVE_RCU
587 bool "RCU debugging: prove RCU correctness"
588 depends on PROVE_LOCKING
589 default n
590 help
591 This feature enables lockdep extensions that check for correct
592 use of RCU APIs. This is currently under development. Say Y
593 if you want to debug RCU usage or help work on the PROVE_RCU
594 feature.
596 Say N if you are unsure.
598 config PROVE_RCU_REPEATEDLY
599 bool "RCU debugging: don't disable PROVE_RCU on first splat"
600 depends on PROVE_RCU
601 default n
602 help
603 By itself, PROVE_RCU will disable checking upon issuing the
604 first warning (or "splat"). This feature prevents such
605 disabling, allowing multiple RCU-lockdep warnings to be printed
606 on a single reboot.
608 Say Y to allow multiple RCU-lockdep warnings per boot.
610 Say N if you are unsure.
612 config SPARSE_RCU_POINTER
613 bool "RCU debugging: sparse-based checks for pointer usage"
614 default n
615 help
616 This feature enables the __rcu sparse annotation for
617 RCU-protected pointers. This annotation will cause sparse
618 to flag any non-RCU used of annotated pointers. This can be
619 helpful when debugging RCU usage. Please note that this feature
620 is not intended to enforce code cleanliness; it is instead merely
621 a debugging aid.
623 Say Y to make sparse flag questionable use of RCU-protected pointers
625 Say N if you are unsure.
627 config LOCKDEP
628 bool
629 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
630 select STACKTRACE
631 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
632 select KALLSYMS
633 select KALLSYMS_ALL
635 config LOCK_STAT
636 bool "Lock usage statistics"
637 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
638 select LOCKDEP
639 select DEBUG_SPINLOCK
640 select DEBUG_MUTEXES
641 select DEBUG_LOCK_ALLOC
642 default n
643 help
644 This feature enables tracking lock contention points
646 For more details, see Documentation/lockstat.txt
648 This also enables lock events required by "perf lock",
649 subcommand of perf.
650 If you want to use "perf lock", you also need to turn on
651 CONFIG_EVENT_TRACING.
653 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
654 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
656 config DEBUG_LOCKDEP
657 bool "Lock dependency engine debugging"
658 depends on DEBUG_KERNEL && LOCKDEP
659 help
660 If you say Y here, the lock dependency engine will do
661 additional runtime checks to debug itself, at the price
662 of more runtime overhead.
664 config TRACE_IRQFLAGS
665 bool
666 help
667 Enables hooks to interrupt enabling and disabling for
668 either tracing or lock debugging.
670 config DEBUG_ATOMIC_SLEEP
671 bool "Sleep inside atomic section checking"
672 select PREEMPT_COUNT
673 depends on DEBUG_KERNEL
674 help
675 If you say Y here, various routines which may sleep will become very
676 noisy if they are called inside atomic sections: when a spinlock is
677 held, inside an rcu read side critical section, inside preempt disabled
678 sections, inside an interrupt, etc...
680 config DEBUG_LOCKING_API_SELFTESTS
681 bool "Locking API boot-time self-tests"
682 depends on DEBUG_KERNEL
683 help
684 Say Y here if you want the kernel to run a short self-test during
685 bootup. The self-test checks whether common types of locking bugs
686 are detected by debugging mechanisms or not. (if you disable
687 lock debugging then those bugs wont be detected of course.)
688 The following locking APIs are covered: spinlocks, rwlocks,
689 mutexes and rwsems.
691 config STACKTRACE
692 bool
693 depends on STACKTRACE_SUPPORT
695 config DEBUG_STACK_USAGE
696 bool "Stack utilization instrumentation"
697 depends on DEBUG_KERNEL
698 help
699 Enables the display of the minimum amount of free stack which each
700 task has ever had available in the sysrq-T and sysrq-P debug output.
702 This option will slow down process creation somewhat.
704 config DEBUG_KOBJECT
705 bool "kobject debugging"
706 depends on DEBUG_KERNEL
707 help
708 If you say Y here, some extra kobject debugging messages will be sent
709 to the syslog.
711 config DEBUG_HIGHMEM
712 bool "Highmem debugging"
713 depends on DEBUG_KERNEL && HIGHMEM
714 help
715 This options enables addition error checking for high memory systems.
716 Disable for production systems.
718 config DEBUG_BUGVERBOSE
719 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
720 depends on BUG
721 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
722 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE
723 default y
724 help
725 Say Y here to make BUG() panics output the file name and line number
726 of the BUG call as well as the EIP and oops trace. This aids
727 debugging but costs about 70-100K of memory.
729 config DEBUG_INFO
730 bool "Compile the kernel with debug info"
731 depends on DEBUG_KERNEL
732 help
733 If you say Y here the resulting kernel image will include
734 debugging info resulting in a larger kernel image.
735 This adds debug symbols to the kernel and modules (gcc -g), and
736 is needed if you intend to use kernel crashdump or binary object
737 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
738 Say Y here only if you plan to debug the kernel.
740 If unsure, say N.
742 config DEBUG_INFO_REDUCED
743 bool "Reduce debugging information"
744 depends on DEBUG_INFO
745 help
746 If you say Y here gcc is instructed to generate less debugging
747 information for structure types. This means that tools that
748 need full debugging information (like kgdb or systemtap) won't
749 be happy. But if you merely need debugging information to
750 resolve line numbers there is no loss. Advantage is that
751 build directory object sizes shrink dramatically over a full
752 DEBUG_INFO build and compile times are reduced too.
753 Only works with newer gcc versions.
755 config DEBUG_VM
756 bool "Debug VM"
757 depends on DEBUG_KERNEL
758 help
759 Enable this to turn on extended checks in the virtual-memory system
760 that may impact performance.
762 If unsure, say N.
764 config DEBUG_VIRTUAL
765 bool "Debug VM translations"
766 depends on DEBUG_KERNEL && X86
767 help
768 Enable some costly sanity checks in virtual to page code. This can
769 catch mistakes with virt_to_page() and friends.
771 If unsure, say N.
773 config DEBUG_NOMMU_REGIONS
774 bool "Debug the global anon/private NOMMU mapping region tree"
775 depends on DEBUG_KERNEL && !MMU
776 help
777 This option causes the global tree of anonymous and private mapping
778 regions to be regularly checked for invalid topology.
780 config DEBUG_WRITECOUNT
781 bool "Debug filesystem writers count"
782 depends on DEBUG_KERNEL
783 help
784 Enable this to catch wrong use of the writers count in struct
785 vfsmount. This will increase the size of each file struct by
786 32 bits.
788 If unsure, say N.
790 config DEBUG_MEMORY_INIT
791 bool "Debug memory initialisation" if EXPERT
792 default !EXPERT
793 help
794 Enable this for additional checks during memory initialisation.
795 The sanity checks verify aspects of the VM such as the memory model
796 and other information provided by the architecture. Verbose
797 information will be printed at KERN_DEBUG loglevel depending
798 on the mminit_loglevel= command-line option.
800 If unsure, say Y
802 config DEBUG_LIST
803 bool "Debug linked list manipulation"
804 depends on DEBUG_KERNEL
805 help
806 Enable this to turn on extended checks in the linked-list
807 walking routines.
809 If unsure, say N.
811 config TEST_LIST_SORT
812 bool "Linked list sorting test"
813 depends on DEBUG_KERNEL
814 help
815 Enable this to turn on 'list_sort()' function test. This test is
816 executed only once during system boot, so affects only boot time.
818 If unsure, say N.
820 config DEBUG_SG
821 bool "Debug SG table operations"
822 depends on DEBUG_KERNEL
823 help
824 Enable this to turn on checks on scatter-gather tables. This can
825 help find problems with drivers that do not properly initialize
826 their sg tables.
828 If unsure, say N.
830 config DEBUG_NOTIFIERS
831 bool "Debug notifier call chains"
832 depends on DEBUG_KERNEL
833 help
834 Enable this to turn on sanity checking for notifier call chains.
835 This is most useful for kernel developers to make sure that
836 modules properly unregister themselves from notifier chains.
837 This is a relatively cheap check but if you care about maximum
838 performance, say N.
840 config DEBUG_CREDENTIALS
841 bool "Debug credential management"
842 depends on DEBUG_KERNEL
843 help
844 Enable this to turn on some debug checking for credential
845 management. The additional code keeps track of the number of
846 pointers from task_structs to any given cred struct, and checks to
847 see that this number never exceeds the usage count of the cred
848 struct.
850 Furthermore, if SELinux is enabled, this also checks that the
851 security pointer in the cred struct is never seen to be invalid.
853 If unsure, say N.
855 #
856 # Select this config option from the architecture Kconfig, if it
857 # is preferred to always offer frame pointers as a config
858 # option on the architecture (regardless of KERNEL_DEBUG):
859 #
860 config ARCH_WANT_FRAME_POINTERS
861 bool
862 help
864 config FRAME_POINTER
865 bool "Compile the kernel with frame pointers"
866 depends on DEBUG_KERNEL && \
867 (CRIS || M68K || FRV || UML || \
868 AVR32 || SUPERH || BLACKFIN || MN10300) || \
869 ARCH_WANT_FRAME_POINTERS
870 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
871 help
872 If you say Y here the resulting kernel image will be slightly
873 larger and slower, but it gives very useful debugging information
874 in case of kernel bugs. (precise oopses/stacktraces/warnings)
876 config BOOT_PRINTK_DELAY
877 bool "Delay each boot printk message by N milliseconds"
878 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
879 help
880 This build option allows you to read kernel boot messages
881 by inserting a short delay after each one. The delay is
882 specified in milliseconds on the kernel command line,
883 using "boot_delay=N".
885 It is likely that you would also need to use "lpj=M" to preset
886 the "loops per jiffie" value.
887 See a previous boot log for the "lpj" value to use for your
888 system, and then set "lpj=M" before setting "boot_delay=N".
889 NOTE: Using this option may adversely affect SMP systems.
890 I.e., processors other than the first one may not boot up.
891 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect
892 what it believes to be lockup conditions.
894 config RCU_TORTURE_TEST
895 tristate "torture tests for RCU"
896 depends on DEBUG_KERNEL
897 default n
898 help
899 This option provides a kernel module that runs torture tests
900 on the RCU infrastructure. The kernel module may be built
901 after the fact on the running kernel to be tested, if desired.
903 Say Y here if you want RCU torture tests to be built into
904 the kernel.
905 Say M if you want the RCU torture tests to build as a module.
906 Say N if you are unsure.
908 config RCU_TORTURE_TEST_RUNNABLE
909 bool "torture tests for RCU runnable by default"
910 depends on RCU_TORTURE_TEST = y
911 default n
912 help
913 This option provides a way to build the RCU torture tests
914 directly into the kernel without them starting up at boot
915 time. You can use /proc/sys/kernel/rcutorture_runnable
916 to manually override this setting. This /proc file is
917 available only when the RCU torture tests have been built
918 into the kernel.
920 Say Y here if you want the RCU torture tests to start during
921 boot (you probably don't).
922 Say N here if you want the RCU torture tests to start only
923 after being manually enabled via /proc.
925 config RCU_CPU_STALL_TIMEOUT
926 int "RCU CPU stall timeout in seconds"
927 depends on TREE_RCU || TREE_PREEMPT_RCU
928 range 3 300
929 default 60
930 help
931 If a given RCU grace period extends more than the specified
932 number of seconds, a CPU stall warning is printed. If the
933 RCU grace period persists, additional CPU stall warnings are
934 printed at more widely spaced intervals.
936 config RCU_CPU_STALL_VERBOSE
937 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
938 depends on TREE_PREEMPT_RCU
939 default y
940 help
941 This option causes RCU to printk detailed per-task information
942 for any tasks that are stalling the current RCU grace period.
944 Say N if you are unsure.
946 Say Y if you want to enable such checks.
948 config RCU_CPU_STALL_INFO
949 bool "Print additional diagnostics on RCU CPU stall"
950 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
951 default n
952 help
953 For each stalled CPU that is aware of the current RCU grace
954 period, print out additional per-CPU diagnostic information
955 regarding scheduling-clock ticks, idle state, and,
956 for RCU_FAST_NO_HZ kernels, idle-entry state.
958 Say N if you are unsure.
960 Say Y if you want to enable such diagnostics.
962 config RCU_TRACE
963 bool "Enable tracing for RCU"
964 depends on DEBUG_KERNEL
965 help
966 This option provides tracing in RCU which presents stats
967 in debugfs for debugging RCU implementation.
969 Say Y here if you want to enable RCU tracing
970 Say N if you are unsure.
972 config KPROBES_SANITY_TEST
973 bool "Kprobes sanity tests"
974 depends on DEBUG_KERNEL
975 depends on KPROBES
976 default n
977 help
978 This option provides for testing basic kprobes functionality on
979 boot. A sample kprobe, jprobe and kretprobe are inserted and
980 verified for functionality.
982 Say N if you are unsure.
984 config BACKTRACE_SELF_TEST
985 tristate "Self test for the backtrace code"
986 depends on DEBUG_KERNEL
987 default n
988 help
989 This option provides a kernel module that can be used to test
990 the kernel stack backtrace code. This option is not useful
991 for distributions or general kernels, but only for kernel
992 developers working on architecture code.
994 Note that if you want to also test saved backtraces, you will
995 have to enable STACKTRACE as well.
997 Say N if you are unsure.
999 config DEBUG_BLOCK_EXT_DEVT
1000 bool "Force extended block device numbers and spread them"
1001 depends on DEBUG_KERNEL
1002 depends on BLOCK
1003 default n
1004 help
1005 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
1006 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
1007 YOU ARE DOING. Distros, please enable this and fix whatever
1008 is broken.
1010 Conventionally, block device numbers are allocated from
1011 predetermined contiguous area. However, extended block area
1012 may introduce non-contiguous block device numbers. This
1013 option forces most block device numbers to be allocated from
1014 the extended space and spreads them to discover kernel or
1015 userland code paths which assume predetermined contiguous
1016 device number allocation.
1018 Note that turning on this debug option shuffles all the
1019 device numbers for all IDE and SCSI devices including libata
1020 ones, so root partition specified using device number
1021 directly (via rdev or root=MAJ:MIN) won't work anymore.
1022 Textual device names (root=/dev/sdXn) will continue to work.
1024 Say N if you are unsure.
1026 config DEBUG_FORCE_WEAK_PER_CPU
1027 bool "Force weak per-cpu definitions"
1028 depends on DEBUG_KERNEL
1029 help
1030 s390 and alpha require percpu variables in modules to be
1031 defined weak to work around addressing range issue which
1032 puts the following two restrictions on percpu variable
1033 definitions.
1035 1. percpu symbols must be unique whether static or not
1036 2. percpu variables can't be defined inside a function
1038 To ensure that generic code follows the above rules, this
1039 option forces all percpu variables to be defined as weak.
1041 config DEBUG_PER_CPU_MAPS
1042 bool "Debug access to per_cpu maps"
1043 depends on DEBUG_KERNEL
1044 depends on SMP
1045 help
1046 Say Y to verify that the per_cpu map being accessed has
1047 been set up. This adds a fair amount of code to kernel memory
1048 and decreases performance.
1050 Say N if unsure.
1052 config LKDTM
1053 tristate "Linux Kernel Dump Test Tool Module"
1054 depends on DEBUG_FS
1055 depends on BLOCK
1056 default n
1057 help
1058 This module enables testing of the different dumping mechanisms by
1059 inducing system failures at predefined crash points.
1060 If you don't need it: say N
1061 Choose M here to compile this code as a module. The module will be
1062 called lkdtm.
1064 Documentation on how to use the module can be found in
1065 Documentation/fault-injection/provoke-crashes.txt
1067 config CPU_NOTIFIER_ERROR_INJECT
1068 tristate "CPU notifier error injection module"
1069 depends on HOTPLUG_CPU && DEBUG_KERNEL
1070 help
1071 This option provides a kernel module that can be used to test
1072 the error handling of the cpu notifiers
1074 To compile this code as a module, choose M here: the module will
1075 be called cpu-notifier-error-inject.
1077 If unsure, say N.
1079 config FAULT_INJECTION
1080 bool "Fault-injection framework"
1081 depends on DEBUG_KERNEL
1082 help
1083 Provide fault-injection framework.
1084 For more details, see Documentation/fault-injection/.
1086 config FAILSLAB
1087 bool "Fault-injection capability for kmalloc"
1088 depends on FAULT_INJECTION
1089 depends on SLAB || SLUB
1090 help
1091 Provide fault-injection capability for kmalloc.
1093 config FAIL_PAGE_ALLOC
1094 bool "Fault-injection capabilitiy for alloc_pages()"
1095 depends on FAULT_INJECTION
1096 help
1097 Provide fault-injection capability for alloc_pages().
1099 config FAIL_MAKE_REQUEST
1100 bool "Fault-injection capability for disk IO"
1101 depends on FAULT_INJECTION && BLOCK
1102 help
1103 Provide fault-injection capability for disk IO.
1105 config FAIL_IO_TIMEOUT
1106 bool "Fault-injection capability for faking disk interrupts"
1107 depends on FAULT_INJECTION && BLOCK
1108 help
1109 Provide fault-injection capability on end IO handling. This
1110 will make the block layer "forget" an interrupt as configured,
1111 thus exercising the error handling.
1113 Only works with drivers that use the generic timeout handling,
1114 for others it wont do anything.
1116 config FAIL_MMC_REQUEST
1117 bool "Fault-injection capability for MMC IO"
1118 select DEBUG_FS
1119 depends on FAULT_INJECTION && MMC
1120 help
1121 Provide fault-injection capability for MMC IO.
1122 This will make the mmc core return data errors. This is
1123 useful to test the error handling in the mmc block device
1124 and to test how the mmc host driver handles retries from
1125 the block device.
1127 config FAULT_INJECTION_DEBUG_FS
1128 bool "Debugfs entries for fault-injection capabilities"
1129 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1130 help
1131 Enable configuration of fault-injection capabilities via debugfs.
1133 config FAULT_INJECTION_STACKTRACE_FILTER
1134 bool "stacktrace filter for fault-injection capabilities"
1135 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1136 depends on !X86_64
1137 select STACKTRACE
1138 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1139 help
1140 Provide stacktrace filter for fault-injection capabilities
1142 config LATENCYTOP
1143 bool "Latency measuring infrastructure"
1144 depends on HAVE_LATENCYTOP_SUPPORT
1145 depends on DEBUG_KERNEL
1146 depends on STACKTRACE_SUPPORT
1147 depends on PROC_FS
1148 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
1149 select KALLSYMS
1150 select KALLSYMS_ALL
1151 select STACKTRACE
1152 select SCHEDSTATS
1153 select SCHED_DEBUG
1154 help
1155 Enable this option if you want to use the LatencyTOP tool
1156 to find out which userspace is blocking on what kernel operations.
1158 source mm/Kconfig.debug
1159 source kernel/trace/Kconfig
1161 config PROVIDE_OHCI1394_DMA_INIT
1162 bool "Remote debugging over FireWire early on boot"
1163 depends on PCI && X86
1164 help
1165 If you want to debug problems which hang or crash the kernel early
1166 on boot and the crashing machine has a FireWire port, you can use
1167 this feature to remotely access the memory of the crashed machine
1168 over FireWire. This employs remote DMA as part of the OHCI1394
1169 specification which is now the standard for FireWire controllers.
1171 With remote DMA, you can monitor the printk buffer remotely using
1172 firescope and access all memory below 4GB using fireproxy from gdb.
1173 Even controlling a kernel debugger is possible using remote DMA.
1175 Usage:
1177 If ohci1394_dma=early is used as boot parameter, it will initialize
1178 all OHCI1394 controllers which are found in the PCI config space.
1180 As all changes to the FireWire bus such as enabling and disabling
1181 devices cause a bus reset and thereby disable remote DMA for all
1182 devices, be sure to have the cable plugged and FireWire enabled on
1183 the debugging host before booting the debug target for debugging.
1185 This code (~1k) is freed after boot. By then, the firewire stack
1186 in charge of the OHCI-1394 controllers should be used instead.
1188 See Documentation/debugging-via-ohci1394.txt for more information.
1190 config FIREWIRE_OHCI_REMOTE_DMA
1191 bool "Remote debugging over FireWire with firewire-ohci"
1192 depends on FIREWIRE_OHCI
1193 help
1194 This option lets you use the FireWire bus for remote debugging
1195 with help of the firewire-ohci driver. It enables unfiltered
1196 remote DMA in firewire-ohci.
1197 See Documentation/debugging-via-ohci1394.txt for more information.
1199 If unsure, say N.
1201 config BUILD_DOCSRC
1202 bool "Build targets in Documentation/ tree"
1203 depends on HEADERS_CHECK
1204 help
1205 This option attempts to build objects from the source files in the
1206 kernel Documentation/ tree.
1208 Say N if you are unsure.
1210 config DYNAMIC_DEBUG
1211 bool "Enable dynamic printk() support"
1212 default n
1213 depends on PRINTK
1214 depends on DEBUG_FS
1215 help
1217 Compiles debug level messages into the kernel, which would not
1218 otherwise be available at runtime. These messages can then be
1219 enabled/disabled based on various levels of scope - per source file,
1220 function, module, format string, and line number. This mechanism
1221 implicitly compiles in all pr_debug() and dev_dbg() calls, which
1222 enlarges the kernel text size by about 2%.
1224 If a source file is compiled with DEBUG flag set, any
1225 pr_debug() calls in it are enabled by default, but can be
1226 disabled at runtime as below. Note that DEBUG flag is
1227 turned on by many CONFIG_*DEBUG* options.
1229 Usage:
1231 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1232 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1233 filesystem must first be mounted before making use of this feature.
1234 We refer the control file as: <debugfs>/dynamic_debug/control. This
1235 file contains a list of the debug statements that can be enabled. The
1236 format for each line of the file is:
1238 filename:lineno [module]function flags format
1240 filename : source file of the debug statement
1241 lineno : line number of the debug statement
1242 module : module that contains the debug statement
1243 function : function that contains the debug statement
1244 flags : '=p' means the line is turned 'on' for printing
1245 format : the format used for the debug statement
1247 From a live system:
1249 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1250 # filename:lineno [module]function flags format
1251 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
1252 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
1253 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"
1255 Example usage:
1257 // enable the message at line 1603 of file svcsock.c
1258 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1259 <debugfs>/dynamic_debug/control
1261 // enable all the messages in file svcsock.c
1262 nullarbor:~ # echo -n 'file svcsock.c +p' >
1263 <debugfs>/dynamic_debug/control
1265 // enable all the messages in the NFS server module
1266 nullarbor:~ # echo -n 'module nfsd +p' >
1267 <debugfs>/dynamic_debug/control
1269 // enable all 12 messages in the function svc_process()
1270 nullarbor:~ # echo -n 'func svc_process +p' >
1271 <debugfs>/dynamic_debug/control
1273 // disable all 12 messages in the function svc_process()
1274 nullarbor:~ # echo -n 'func svc_process -p' >
1275 <debugfs>/dynamic_debug/control
1277 See Documentation/dynamic-debug-howto.txt for additional information.
1279 config DMA_API_DEBUG
1280 bool "Enable debugging of DMA-API usage"
1281 depends on HAVE_DMA_API_DEBUG
1282 help
1283 Enable this option to debug the use of the DMA API by device drivers.
1284 With this option you will be able to detect common bugs in device
1285 drivers like double-freeing of DMA mappings or freeing mappings that
1286 were never allocated.
1287 This option causes a performance degredation. Use only if you want
1288 to debug device drivers. If unsure, say N.
1290 config ATOMIC64_SELFTEST
1291 bool "Perform an atomic64_t self-test at boot"
1292 help
1293 Enable this option to test the atomic64_t functions at boot.
1295 If unsure, say N.
1297 config ASYNC_RAID6_TEST
1298 tristate "Self test for hardware accelerated raid6 recovery"
1299 depends on ASYNC_RAID6_RECOV
1300 select ASYNC_MEMCPY
1301 ---help---
1302 This is a one-shot self test that permutes through the
1303 recovery of all the possible two disk failure scenarios for a
1304 N-disk array. Recovery is performed with the asynchronous
1305 raid6 recovery routines, and will optionally use an offload
1306 engine if one is available.
1308 If unsure, say N.
1310 source "samples/Kconfig"
1312 source "lib/Kconfig.kgdb"
1314 source "lib/Kconfig.kmemcheck"
1316 config TEST_KSTRTOX
1317 tristate "Test kstrto*() family of functions at runtime"