3 bool "Show timing information on printks"
6 Selecting this option causes timing information to be
7 included in printk output. This allows you to measure
8 the interval between kernel operations, including bootup
9 operations. This is useful for identifying long delays
12 config ENABLE_WARN_DEPRECATED
13 bool "Enable __deprecated logic"
16 Enable the __deprecated logic in the kernel build.
17 Disable this to suppress the "warning: 'foo' is deprecated
18 (declared at kernel/power/somefile.c:1234)" messages.
20 config ENABLE_MUST_CHECK
21 bool "Enable __must_check logic"
24 Enable the __must_check logic in the kernel build. Disable this to
25 suppress the "warning: ignoring return value of 'foo', declared with
26 attribute warn_unused_result" messages.
29 int "Warn for stack frames larger than (needs gcc 4.4)"
31 default 1024 if !64BIT
34 Tell gcc to warn at build time for stack frames larger than this.
35 Setting this too low will cause a lot of warnings.
36 Setting it to 0 disables the warning.
40 bool "Magic SysRq key"
43 If you say Y here, you will have some control over the system even
44 if the system crashes for example during kernel debugging (e.g., you
45 will be able to flush the buffer cache to disk, reboot the system
46 immediately or dump some status information). This is accomplished
47 by pressing various keys while holding SysRq (Alt+PrintScreen). It
48 also works on a serial console (on PC hardware at least), if you
49 send a BREAK and then within 5 seconds a command keypress. The
50 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
51 unless you really know what this hack does.
54 bool "Strip assembler-generated symbols during link"
57 Strip internal assembler-generated symbols during a link (symbols
58 that look like '.Lxxx') so they don't pollute the output of
59 get_wchan() and suchlike.
62 bool "Enable unused/obsolete exported symbols"
65 Unused but exported symbols make the kernel needlessly bigger. For
66 that reason most of these unused exports will soon be removed. This
67 option is provided temporarily to provide a transition period in case
68 some external kernel module needs one of these symbols anyway. If you
69 encounter such a case in your module, consider if you are actually
70 using the right API. (rationale: since nobody in the kernel is using
71 this in a module, there is a pretty good chance it's actually the
72 wrong interface to use). If you really need the symbol, please send a
73 mail to the linux kernel mailing list mentioning the symbol and why
74 you really need it, and what the merge plan to the mainline kernel for
78 bool "Debug Filesystem"
80 debugfs is a virtual file system that kernel developers use to put
81 debugging files into. Enable this option to be able to read and
84 For detailed documentation on the debugfs API, see
85 Documentation/DocBook/filesystems.
90 bool "Run 'make headers_check' when building vmlinux"
93 This option will extract the user-visible kernel headers whenever
94 building the kernel, and will run basic sanity checks on them to
95 ensure that exported files do not attempt to include files which
96 were not exported, etc.
98 If you're making modifications to header files which are
99 relevant for userspace, say 'Y', and check the headers
100 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
101 your build tree), to make sure they're suitable.
103 config DEBUG_SECTION_MISMATCH
104 bool "Enable full Section mismatch analysis"
106 The section mismatch analysis checks if there are illegal
107 references from one section to another section.
108 Linux will during link or during runtime drop some sections
109 and any use of code/data previously in these sections will
110 most likely result in an oops.
111 In the code functions and variables are annotated with
112 __init, __devinit etc. (see full list in include/linux/init.h)
113 which results in the code/data being placed in specific sections.
114 The section mismatch analysis is always done after a full
115 kernel build but enabling this option will in addition
117 - Add the option -fno-inline-functions-called-once to gcc
118 When inlining a function annotated __init in a non-init
119 function we would lose the section information and thus
120 the analysis would not catch the illegal reference.
121 This option tells gcc to inline less but will also
122 result in a larger kernel.
123 - Run the section mismatch analysis for each module/built-in.o
124 When we run the section mismatch analysis on vmlinux.o we
125 lose valueble information about where the mismatch was
127 Running the analysis for each module/built-in.o file
128 will tell where the mismatch happens much closer to the
129 source. The drawback is that we will report the same
130 mismatch at least twice.
131 - Enable verbose reporting from modpost to help solving
132 the section mismatches reported.
135 bool "Kernel debugging"
137 Say Y here if you are developing drivers or trying to debug and
138 identify kernel problems.
141 bool "Debug shared IRQ handlers"
142 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
144 Enable this to generate a spurious interrupt as soon as a shared
145 interrupt handler is registered, and just before one is deregistered.
146 Drivers ought to be able to handle interrupts coming in at those
147 points; some don't and need to be caught.
149 config LOCKUP_DETECTOR
150 bool "Detect Hard and Soft Lockups"
151 depends on DEBUG_KERNEL && !S390
153 Say Y here to enable the kernel to act as a watchdog to detect
154 hard and soft lockups.
156 Softlockups are bugs that cause the kernel to loop in kernel
157 mode for more than 60 seconds, without giving other tasks a
158 chance to run. The current stack trace is displayed upon
159 detection and the system will stay locked up.
161 Hardlockups are bugs that cause the CPU to loop in kernel mode
162 for more than 60 seconds, without letting other interrupts have a
163 chance to run. The current stack trace is displayed upon detection
164 and the system will stay locked up.
166 The overhead should be minimal. A periodic hrtimer runs to
167 generate interrupts and kick the watchdog task every 10-12 seconds.
168 An NMI is generated every 60 seconds or so to check for hardlockups.
170 config HARDLOCKUP_DETECTOR
171 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \
172 !ARCH_HAS_NMI_WATCHDOG
174 config BOOTPARAM_HARDLOCKUP_PANIC
175 bool "Panic (Reboot) On Hard Lockups"
176 depends on LOCKUP_DETECTOR
178 Say Y here to enable the kernel to panic on "hard lockups",
179 which are bugs that cause the kernel to loop in kernel
180 mode with interrupts disabled for more than 60 seconds.
184 config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
186 depends on LOCKUP_DETECTOR
188 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
189 default 1 if BOOTPARAM_HARDLOCKUP_PANIC
191 config BOOTPARAM_SOFTLOCKUP_PANIC
192 bool "Panic (Reboot) On Soft Lockups"
193 depends on LOCKUP_DETECTOR
195 Say Y here to enable the kernel to panic on "soft lockups",
196 which are bugs that cause the kernel to loop in kernel
197 mode for more than 60 seconds, without giving other tasks a
200 The panic can be used in combination with panic_timeout,
201 to cause the system to reboot automatically after a
202 lockup has been detected. This feature is useful for
203 high-availability systems that have uptime guarantees and
204 where a lockup must be resolved ASAP.
208 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
210 depends on LOCKUP_DETECTOR
212 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
213 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
215 config DETECT_HUNG_TASK
216 bool "Detect Hung Tasks"
217 depends on DEBUG_KERNEL
218 default DETECT_SOFTLOCKUP
220 Say Y here to enable the kernel to detect "hung tasks",
221 which are bugs that cause the task to be stuck in
222 uninterruptible "D" state indefinitiley.
224 When a hung task is detected, the kernel will print the
225 current stack trace (which you should report), but the
226 task will stay in uninterruptible state. If lockdep is
227 enabled then all held locks will also be reported. This
228 feature has negligible overhead.
230 config BOOTPARAM_HUNG_TASK_PANIC
231 bool "Panic (Reboot) On Hung Tasks"
232 depends on DETECT_HUNG_TASK
234 Say Y here to enable the kernel to panic on "hung tasks",
235 which are bugs that cause the kernel to leave a task stuck
236 in uninterruptible "D" state.
238 The panic can be used in combination with panic_timeout,
239 to cause the system to reboot automatically after a
240 hung task has been detected. This feature is useful for
241 high-availability systems that have uptime guarantees and
242 where a hung tasks must be resolved ASAP.
246 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
248 depends on DETECT_HUNG_TASK
250 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
251 default 1 if BOOTPARAM_HUNG_TASK_PANIC
254 bool "Collect scheduler debugging info"
255 depends on DEBUG_KERNEL && PROC_FS
258 If you say Y here, the /proc/sched_debug file will be provided
259 that can help debug the scheduler. The runtime overhead of this
263 bool "Collect scheduler statistics"
264 depends on DEBUG_KERNEL && PROC_FS
266 If you say Y here, additional code will be inserted into the
267 scheduler and related routines to collect statistics about
268 scheduler behavior and provide them in /proc/schedstat. These
269 stats may be useful for both tuning and debugging the scheduler
270 If you aren't debugging the scheduler or trying to tune a specific
271 application, you can say N to avoid the very slight overhead
275 bool "Collect kernel timers statistics"
276 depends on DEBUG_KERNEL && PROC_FS
278 If you say Y here, additional code will be inserted into the
279 timer routines to collect statistics about kernel timers being
280 reprogrammed. The statistics can be read from /proc/timer_stats.
281 The statistics collection is started by writing 1 to /proc/timer_stats,
282 writing 0 stops it. This feature is useful to collect information
283 about timer usage patterns in kernel and userspace. This feature
284 is lightweight if enabled in the kernel config but not activated
285 (it defaults to deactivated on bootup and will only be activated
286 if some application like powertop activates it explicitly).
289 bool "Debug object operations"
290 depends on DEBUG_KERNEL
292 If you say Y here, additional code will be inserted into the
293 kernel to track the life time of various objects and validate
294 the operations on those objects.
296 config DEBUG_OBJECTS_SELFTEST
297 bool "Debug objects selftest"
298 depends on DEBUG_OBJECTS
300 This enables the selftest of the object debug code.
302 config DEBUG_OBJECTS_FREE
303 bool "Debug objects in freed memory"
304 depends on DEBUG_OBJECTS
306 This enables checks whether a k/v free operation frees an area
307 which contains an object which has not been deactivated
308 properly. This can make kmalloc/kfree-intensive workloads
311 config DEBUG_OBJECTS_TIMERS
312 bool "Debug timer objects"
313 depends on DEBUG_OBJECTS
315 If you say Y here, additional code will be inserted into the
316 timer routines to track the life time of timer objects and
317 validate the timer operations.
319 config DEBUG_OBJECTS_WORK
320 bool "Debug work objects"
321 depends on DEBUG_OBJECTS
323 If you say Y here, additional code will be inserted into the
324 work queue routines to track the life time of work objects and
325 validate the work operations.
327 config DEBUG_OBJECTS_RCU_HEAD
328 bool "Debug RCU callbacks objects"
329 depends on DEBUG_OBJECTS && PREEMPT
331 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
333 config DEBUG_OBJECTS_PERCPU_COUNTER
334 bool "Debug percpu counter objects"
335 depends on DEBUG_OBJECTS
337 If you say Y here, additional code will be inserted into the
338 percpu counter routines to track the life time of percpu counter
339 objects and validate the percpu counter operations.
341 config DEBUG_OBJECTS_ENABLE_DEFAULT
342 int "debug_objects bootup default value (0-1)"
345 depends on DEBUG_OBJECTS
347 Debug objects boot parameter default value
350 bool "Debug slab memory allocations"
351 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
353 Say Y here to have the kernel do limited verification on memory
354 allocation as well as poisoning memory on free to catch use of freed
355 memory. This can make kmalloc/kfree-intensive workloads much slower.
357 config DEBUG_SLAB_LEAK
358 bool "Memory leak debugging"
359 depends on DEBUG_SLAB
362 bool "SLUB debugging on by default"
363 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
366 Boot with debugging on by default. SLUB boots by default with
367 the runtime debug capabilities switched off. Enabling this is
368 equivalent to specifying the "slub_debug" parameter on boot.
369 There is no support for more fine grained debug control like
370 possible with slub_debug=xxx. SLUB debugging may be switched
371 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
376 bool "Enable SLUB performance statistics"
377 depends on SLUB && SYSFS
379 SLUB statistics are useful to debug SLUBs allocation behavior in
380 order find ways to optimize the allocator. This should never be
381 enabled for production use since keeping statistics slows down
382 the allocator by a few percentage points. The slabinfo command
383 supports the determination of the most active slabs to figure
384 out which slabs are relevant to a particular load.
385 Try running: slabinfo -DA
387 config DEBUG_KMEMLEAK
388 bool "Kernel memory leak detector"
389 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
390 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE)
392 select DEBUG_FS if SYSFS
393 select STACKTRACE if STACKTRACE_SUPPORT
397 Say Y here if you want to enable the memory leak
398 detector. The memory allocation/freeing is traced in a way
399 similar to the Boehm's conservative garbage collector, the
400 difference being that the orphan objects are not freed but
401 only shown in /sys/kernel/debug/kmemleak. Enabling this
402 feature will introduce an overhead to memory
403 allocations. See Documentation/kmemleak.txt for more
406 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
407 of finding leaks due to the slab objects poisoning.
409 In order to access the kmemleak file, debugfs needs to be
410 mounted (usually at /sys/kernel/debug).
412 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
413 int "Maximum kmemleak early log entries"
414 depends on DEBUG_KMEMLEAK
418 Kmemleak must track all the memory allocations to avoid
419 reporting false positives. Since memory may be allocated or
420 freed before kmemleak is initialised, an early log buffer is
421 used to store these actions. If kmemleak reports "early log
422 buffer exceeded", please increase this value.
424 config DEBUG_KMEMLEAK_TEST
425 tristate "Simple test for the kernel memory leak detector"
426 depends on DEBUG_KMEMLEAK
428 Say Y or M here to build a test for the kernel memory leak
429 detector. This option enables a module that explicitly leaks
434 config DEBUG_KMEMLEAK_DEFAULT_OFF
435 bool "Default kmemleak to off"
436 depends on DEBUG_KMEMLEAK
438 Say Y here to disable kmemleak by default. It can then be enabled
439 on the command line via kmemleak=on.
442 bool "Debug preemptible kernel"
443 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
446 If you say Y here then the kernel will use a debug variant of the
447 commonly used smp_processor_id() function and will print warnings
448 if kernel code uses it in a preemption-unsafe way. Also, the kernel
449 will detect preemption count underflows.
451 config DEBUG_RT_MUTEXES
452 bool "RT Mutex debugging, deadlock detection"
453 depends on DEBUG_KERNEL && RT_MUTEXES
455 This allows rt mutex semantics violations and rt mutex related
456 deadlocks (lockups) to be detected and reported automatically.
461 depends on DEBUG_RT_MUTEXES
463 config RT_MUTEX_TESTER
464 bool "Built-in scriptable tester for rt-mutexes"
465 depends on DEBUG_KERNEL && RT_MUTEXES
467 This option enables a rt-mutex tester.
469 config DEBUG_SPINLOCK
470 bool "Spinlock and rw-lock debugging: basic checks"
471 depends on DEBUG_KERNEL
473 Say Y here and build SMP to catch missing spinlock initialization
474 and certain other kinds of spinlock errors commonly made. This is
475 best used in conjunction with the NMI watchdog so that spinlock
476 deadlocks are also debuggable.
479 bool "Mutex debugging: basic checks"
480 depends on DEBUG_KERNEL
482 This feature allows mutex semantics violations to be detected and
485 config DEBUG_LOCK_ALLOC
486 bool "Lock debugging: detect incorrect freeing of live locks"
487 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
488 select DEBUG_SPINLOCK
492 This feature will check whether any held lock (spinlock, rwlock,
493 mutex or rwsem) is incorrectly freed by the kernel, via any of the
494 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
495 vfree(), etc.), whether a live lock is incorrectly reinitialized via
496 spin_lock_init()/mutex_init()/etc., or whether there is any lock
497 held during task exit.
500 bool "Lock debugging: prove locking correctness"
501 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
503 select DEBUG_SPINLOCK
505 select DEBUG_LOCK_ALLOC
506 select TRACE_IRQFLAGS
509 This feature enables the kernel to prove that all locking
510 that occurs in the kernel runtime is mathematically
511 correct: that under no circumstance could an arbitrary (and
512 not yet triggered) combination of observed locking
513 sequences (on an arbitrary number of CPUs, running an
514 arbitrary number of tasks and interrupt contexts) cause a
517 In short, this feature enables the kernel to report locking
518 related deadlocks before they actually occur.
520 The proof does not depend on how hard and complex a
521 deadlock scenario would be to trigger: how many
522 participant CPUs, tasks and irq-contexts would be needed
523 for it to trigger. The proof also does not depend on
524 timing: if a race and a resulting deadlock is possible
525 theoretically (no matter how unlikely the race scenario
526 is), it will be proven so and will immediately be
527 reported by the kernel (once the event is observed that
528 makes the deadlock theoretically possible).
530 If a deadlock is impossible (i.e. the locking rules, as
531 observed by the kernel, are mathematically correct), the
532 kernel reports nothing.
534 NOTE: this feature can also be enabled for rwlocks, mutexes
535 and rwsems - in which case all dependencies between these
536 different locking variants are observed and mapped too, and
537 the proof of observed correctness is also maintained for an
538 arbitrary combination of these separate locking variants.
540 For more details, see Documentation/lockdep-design.txt.
543 bool "RCU debugging: prove RCU correctness"
544 depends on PROVE_LOCKING
547 This feature enables lockdep extensions that check for correct
548 use of RCU APIs. This is currently under development. Say Y
549 if you want to debug RCU usage or help work on the PROVE_RCU
552 Say N if you are unsure.
554 config PROVE_RCU_REPEATEDLY
555 bool "RCU debugging: don't disable PROVE_RCU on first splat"
559 By itself, PROVE_RCU will disable checking upon issuing the
560 first warning (or "splat"). This feature prevents such
561 disabling, allowing multiple RCU-lockdep warnings to be printed
564 Say Y to allow multiple RCU-lockdep warnings per boot.
566 Say N if you are unsure.
568 config SPARSE_RCU_POINTER
569 bool "RCU debugging: sparse-based checks for pointer usage"
572 This feature enables the __rcu sparse annotation for
573 RCU-protected pointers. This annotation will cause sparse
574 to flag any non-RCU used of annotated pointers. This can be
575 helpful when debugging RCU usage. Please note that this feature
576 is not intended to enforce code cleanliness; it is instead merely
579 Say Y to make sparse flag questionable use of RCU-protected pointers
581 Say N if you are unsure.
585 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
587 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
592 bool "Lock usage statistics"
593 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
595 select DEBUG_SPINLOCK
597 select DEBUG_LOCK_ALLOC
600 This feature enables tracking lock contention points
602 For more details, see Documentation/lockstat.txt
604 This also enables lock events required by "perf lock",
606 If you want to use "perf lock", you also need to turn on
607 CONFIG_EVENT_TRACING.
609 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
610 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
613 bool "Lock dependency engine debugging"
614 depends on DEBUG_KERNEL && LOCKDEP
616 If you say Y here, the lock dependency engine will do
617 additional runtime checks to debug itself, at the price
618 of more runtime overhead.
620 config TRACE_IRQFLAGS
623 Enables hooks to interrupt enabling and disabling for
624 either tracing or lock debugging.
626 config DEBUG_SPINLOCK_SLEEP
627 bool "Spinlock debugging: sleep-inside-spinlock checking"
628 depends on DEBUG_KERNEL
630 If you say Y here, various routines which may sleep will become very
631 noisy if they are called with a spinlock held.
633 config DEBUG_LOCKING_API_SELFTESTS
634 bool "Locking API boot-time self-tests"
635 depends on DEBUG_KERNEL
637 Say Y here if you want the kernel to run a short self-test during
638 bootup. The self-test checks whether common types of locking bugs
639 are detected by debugging mechanisms or not. (if you disable
640 lock debugging then those bugs wont be detected of course.)
641 The following locking APIs are covered: spinlocks, rwlocks,
646 depends on STACKTRACE_SUPPORT
649 bool "kobject debugging"
650 depends on DEBUG_KERNEL
652 If you say Y here, some extra kobject debugging messages will be sent
656 bool "Highmem debugging"
657 depends on DEBUG_KERNEL && HIGHMEM
659 This options enables addition error checking for high memory systems.
660 Disable for production systems.
662 config DEBUG_BUGVERBOSE
663 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
665 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
666 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
669 Say Y here to make BUG() panics output the file name and line number
670 of the BUG call as well as the EIP and oops trace. This aids
671 debugging but costs about 70-100K of memory.
674 bool "Compile the kernel with debug info"
675 depends on DEBUG_KERNEL
677 If you say Y here the resulting kernel image will include
678 debugging info resulting in a larger kernel image.
679 This adds debug symbols to the kernel and modules (gcc -g), and
680 is needed if you intend to use kernel crashdump or binary object
681 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
682 Say Y here only if you plan to debug the kernel.
686 config DEBUG_INFO_REDUCED
687 bool "Reduce debugging information"
688 depends on DEBUG_INFO
690 If you say Y here gcc is instructed to generate less debugging
691 information for structure types. This means that tools that
692 need full debugging information (like kgdb or systemtap) won't
693 be happy. But if you merely need debugging information to
694 resolve line numbers there is no loss. Advantage is that
695 build directory object sizes shrink dramatically over a full
696 DEBUG_INFO build and compile times are reduced too.
697 Only works with newer gcc versions.
701 depends on DEBUG_KERNEL
703 Enable this to turn on extended checks in the virtual-memory system
704 that may impact performance.
709 bool "Debug VM translations"
710 depends on DEBUG_KERNEL && X86
712 Enable some costly sanity checks in virtual to page code. This can
713 catch mistakes with virt_to_page() and friends.
717 config DEBUG_NOMMU_REGIONS
718 bool "Debug the global anon/private NOMMU mapping region tree"
719 depends on DEBUG_KERNEL && !MMU
721 This option causes the global tree of anonymous and private mapping
722 regions to be regularly checked for invalid topology.
724 config DEBUG_WRITECOUNT
725 bool "Debug filesystem writers count"
726 depends on DEBUG_KERNEL
728 Enable this to catch wrong use of the writers count in struct
729 vfsmount. This will increase the size of each file struct by
734 config DEBUG_MEMORY_INIT
735 bool "Debug memory initialisation" if EXPERT
738 Enable this for additional checks during memory initialisation.
739 The sanity checks verify aspects of the VM such as the memory model
740 and other information provided by the architecture. Verbose
741 information will be printed at KERN_DEBUG loglevel depending
742 on the mminit_loglevel= command-line option.
747 bool "Debug linked list manipulation"
748 depends on DEBUG_KERNEL
750 Enable this to turn on extended checks in the linked-list
755 config TEST_LIST_SORT
756 bool "Linked list sorting test"
757 depends on DEBUG_KERNEL
759 Enable this to turn on 'list_sort()' function test. This test is
760 executed only once during system boot, so affects only boot time.
765 bool "Debug SG table operations"
766 depends on DEBUG_KERNEL
768 Enable this to turn on checks on scatter-gather tables. This can
769 help find problems with drivers that do not properly initialize
774 config DEBUG_NOTIFIERS
775 bool "Debug notifier call chains"
776 depends on DEBUG_KERNEL
778 Enable this to turn on sanity checking for notifier call chains.
779 This is most useful for kernel developers to make sure that
780 modules properly unregister themselves from notifier chains.
781 This is a relatively cheap check but if you care about maximum
784 config DEBUG_CREDENTIALS
785 bool "Debug credential management"
786 depends on DEBUG_KERNEL
788 Enable this to turn on some debug checking for credential
789 management. The additional code keeps track of the number of
790 pointers from task_structs to any given cred struct, and checks to
791 see that this number never exceeds the usage count of the cred
794 Furthermore, if SELinux is enabled, this also checks that the
795 security pointer in the cred struct is never seen to be invalid.
800 # Select this config option from the architecture Kconfig, if it
801 # it is preferred to always offer frame pointers as a config
802 # option on the architecture (regardless of KERNEL_DEBUG):
804 config ARCH_WANT_FRAME_POINTERS
809 bool "Compile the kernel with frame pointers"
810 depends on DEBUG_KERNEL && \
811 (CRIS || M68K || FRV || UML || \
812 AVR32 || SUPERH || BLACKFIN || MN10300) || \
813 ARCH_WANT_FRAME_POINTERS
814 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
816 If you say Y here the resulting kernel image will be slightly
817 larger and slower, but it gives very useful debugging information
818 in case of kernel bugs. (precise oopses/stacktraces/warnings)
820 config BOOT_PRINTK_DELAY
821 bool "Delay each boot printk message by N milliseconds"
822 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
824 This build option allows you to read kernel boot messages
825 by inserting a short delay after each one. The delay is
826 specified in milliseconds on the kernel command line,
827 using "boot_delay=N".
829 It is likely that you would also need to use "lpj=M" to preset
830 the "loops per jiffie" value.
831 See a previous boot log for the "lpj" value to use for your
832 system, and then set "lpj=M" before setting "boot_delay=N".
833 NOTE: Using this option may adversely affect SMP systems.
834 I.e., processors other than the first one may not boot up.
835 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
836 what it believes to be lockup conditions.
838 config RCU_TORTURE_TEST
839 tristate "torture tests for RCU"
840 depends on DEBUG_KERNEL
843 This option provides a kernel module that runs torture tests
844 on the RCU infrastructure. The kernel module may be built
845 after the fact on the running kernel to be tested, if desired.
847 Say Y here if you want RCU torture tests to be built into
849 Say M if you want the RCU torture tests to build as a module.
850 Say N if you are unsure.
852 config RCU_TORTURE_TEST_RUNNABLE
853 bool "torture tests for RCU runnable by default"
854 depends on RCU_TORTURE_TEST = y
857 This option provides a way to build the RCU torture tests
858 directly into the kernel without them starting up at boot
859 time. You can use /proc/sys/kernel/rcutorture_runnable
860 to manually override this setting. This /proc file is
861 available only when the RCU torture tests have been built
864 Say Y here if you want the RCU torture tests to start during
865 boot (you probably don't).
866 Say N here if you want the RCU torture tests to start only
867 after being manually enabled via /proc.
869 config RCU_CPU_STALL_DETECTOR
870 bool "Check for stalled CPUs delaying RCU grace periods"
871 depends on TREE_RCU || TREE_PREEMPT_RCU
874 This option causes RCU to printk information on which
875 CPUs are delaying the current grace period, but only when
876 the grace period extends for excessive time periods.
878 Say N if you want to disable such checks.
880 Say Y if you are unsure.
882 config RCU_CPU_STALL_TIMEOUT
883 int "RCU CPU stall timeout in seconds"
884 depends on RCU_CPU_STALL_DETECTOR
888 If a given RCU grace period extends more than the specified
889 number of seconds, a CPU stall warning is printed. If the
890 RCU grace period persists, additional CPU stall warnings are
891 printed at more widely spaced intervals.
893 config RCU_CPU_STALL_DETECTOR_RUNNABLE
894 bool "RCU CPU stall checking starts automatically at boot"
895 depends on RCU_CPU_STALL_DETECTOR
898 If set, start checking for RCU CPU stalls immediately on
899 boot. Otherwise, RCU CPU stall checking must be manually
902 Say Y if you are unsure.
904 Say N if you wish to suppress RCU CPU stall checking during boot.
906 config RCU_CPU_STALL_VERBOSE
907 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
908 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
911 This option causes RCU to printk detailed per-task information
912 for any tasks that are stalling the current RCU grace period.
914 Say N if you are unsure.
916 Say Y if you want to enable such checks.
918 config KPROBES_SANITY_TEST
919 bool "Kprobes sanity tests"
920 depends on DEBUG_KERNEL
924 This option provides for testing basic kprobes functionality on
925 boot. A sample kprobe, jprobe and kretprobe are inserted and
926 verified for functionality.
928 Say N if you are unsure.
930 config BACKTRACE_SELF_TEST
931 tristate "Self test for the backtrace code"
932 depends on DEBUG_KERNEL
935 This option provides a kernel module that can be used to test
936 the kernel stack backtrace code. This option is not useful
937 for distributions or general kernels, but only for kernel
938 developers working on architecture code.
940 Note that if you want to also test saved backtraces, you will
941 have to enable STACKTRACE as well.
943 Say N if you are unsure.
945 config DEBUG_BLOCK_EXT_DEVT
946 bool "Force extended block device numbers and spread them"
947 depends on DEBUG_KERNEL
951 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
952 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
953 YOU ARE DOING. Distros, please enable this and fix whatever
956 Conventionally, block device numbers are allocated from
957 predetermined contiguous area. However, extended block area
958 may introduce non-contiguous block device numbers. This
959 option forces most block device numbers to be allocated from
960 the extended space and spreads them to discover kernel or
961 userland code paths which assume predetermined contiguous
962 device number allocation.
964 Note that turning on this debug option shuffles all the
965 device numbers for all IDE and SCSI devices including libata
966 ones, so root partition specified using device number
967 directly (via rdev or root=MAJ:MIN) won't work anymore.
968 Textual device names (root=/dev/sdXn) will continue to work.
970 Say N if you are unsure.
972 config DEBUG_FORCE_WEAK_PER_CPU
973 bool "Force weak per-cpu definitions"
974 depends on DEBUG_KERNEL
976 s390 and alpha require percpu variables in modules to be
977 defined weak to work around addressing range issue which
978 puts the following two restrictions on percpu variable
981 1. percpu symbols must be unique whether static or not
982 2. percpu variables can't be defined inside a function
984 To ensure that generic code follows the above rules, this
985 option forces all percpu variables to be defined as weak.
988 tristate "Linux Kernel Dump Test Tool Module"
993 This module enables testing of the different dumping mechanisms by
994 inducing system failures at predefined crash points.
995 If you don't need it: say N
996 Choose M here to compile this code as a module. The module will be
999 Documentation on how to use the module can be found in
1000 Documentation/fault-injection/provoke-crashes.txt
1002 config CPU_NOTIFIER_ERROR_INJECT
1003 tristate "CPU notifier error injection module"
1004 depends on HOTPLUG_CPU && DEBUG_KERNEL
1006 This option provides a kernel module that can be used to test
1007 the error handling of the cpu notifiers
1009 To compile this code as a module, choose M here: the module will
1010 be called cpu-notifier-error-inject.
1014 config FAULT_INJECTION
1015 bool "Fault-injection framework"
1016 depends on DEBUG_KERNEL
1018 Provide fault-injection framework.
1019 For more details, see Documentation/fault-injection/.
1022 bool "Fault-injection capability for kmalloc"
1023 depends on FAULT_INJECTION
1024 depends on SLAB || SLUB
1026 Provide fault-injection capability for kmalloc.
1028 config FAIL_PAGE_ALLOC
1029 bool "Fault-injection capabilitiy for alloc_pages()"
1030 depends on FAULT_INJECTION
1032 Provide fault-injection capability for alloc_pages().
1034 config FAIL_MAKE_REQUEST
1035 bool "Fault-injection capability for disk IO"
1036 depends on FAULT_INJECTION && BLOCK
1038 Provide fault-injection capability for disk IO.
1040 config FAIL_IO_TIMEOUT
1041 bool "Fault-injection capability for faking disk interrupts"
1042 depends on FAULT_INJECTION && BLOCK
1044 Provide fault-injection capability on end IO handling. This
1045 will make the block layer "forget" an interrupt as configured,
1046 thus exercising the error handling.
1048 Only works with drivers that use the generic timeout handling,
1049 for others it wont do anything.
1051 config FAULT_INJECTION_DEBUG_FS
1052 bool "Debugfs entries for fault-injection capabilities"
1053 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
1055 Enable configuration of fault-injection capabilities via debugfs.
1057 config FAULT_INJECTION_STACKTRACE_FILTER
1058 bool "stacktrace filter for fault-injection capabilities"
1059 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
1062 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
1064 Provide stacktrace filter for fault-injection capabilities
1067 bool "Latency measuring infrastructure"
1068 depends on HAVE_LATENCYTOP_SUPPORT
1069 depends on DEBUG_KERNEL
1070 depends on STACKTRACE_SUPPORT
1072 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
1079 Enable this option if you want to use the LatencyTOP tool
1080 to find out which userspace is blocking on what kernel operations.
1082 config SYSCTL_SYSCALL_CHECK
1083 bool "Sysctl checks"
1086 sys_sysctl uses binary paths that have been found challenging
1087 to properly maintain and use. This enables checks that help
1088 you to keep things correct.
1090 source mm/Kconfig.debug
1091 source kernel/trace/Kconfig
1093 config PROVIDE_OHCI1394_DMA_INIT
1094 bool "Remote debugging over FireWire early on boot"
1095 depends on PCI && X86
1097 If you want to debug problems which hang or crash the kernel early
1098 on boot and the crashing machine has a FireWire port, you can use
1099 this feature to remotely access the memory of the crashed machine
1100 over FireWire. This employs remote DMA as part of the OHCI1394
1101 specification which is now the standard for FireWire controllers.
1103 With remote DMA, you can monitor the printk buffer remotely using
1104 firescope and access all memory below 4GB using fireproxy from gdb.
1105 Even controlling a kernel debugger is possible using remote DMA.
1109 If ohci1394_dma=early is used as boot parameter, it will initialize
1110 all OHCI1394 controllers which are found in the PCI config space.
1112 As all changes to the FireWire bus such as enabling and disabling
1113 devices cause a bus reset and thereby disable remote DMA for all
1114 devices, be sure to have the cable plugged and FireWire enabled on
1115 the debugging host before booting the debug target for debugging.
1117 This code (~1k) is freed after boot. By then, the firewire stack
1118 in charge of the OHCI-1394 controllers should be used instead.
1120 See Documentation/debugging-via-ohci1394.txt for more information.
1122 config FIREWIRE_OHCI_REMOTE_DMA
1123 bool "Remote debugging over FireWire with firewire-ohci"
1124 depends on FIREWIRE_OHCI
1126 This option lets you use the FireWire bus for remote debugging
1127 with help of the firewire-ohci driver. It enables unfiltered
1128 remote DMA in firewire-ohci.
1129 See Documentation/debugging-via-ohci1394.txt for more information.
1134 bool "Build targets in Documentation/ tree"
1135 depends on HEADERS_CHECK
1137 This option attempts to build objects from the source files in the
1138 kernel Documentation/ tree.
1140 Say N if you are unsure.
1142 config DYNAMIC_DEBUG
1143 bool "Enable dynamic printk() support"
1149 Compiles debug level messages into the kernel, which would not
1150 otherwise be available at runtime. These messages can then be
1151 enabled/disabled based on various levels of scope - per source file,
1152 function, module, format string, and line number. This mechanism
1153 implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1154 this compile option is a larger kernel text size of about 2%.
1158 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1159 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1160 filesystem must first be mounted before making use of this feature.
1161 We refer the control file as: <debugfs>/dynamic_debug/control. This
1162 file contains a list of the debug statements that can be enabled. The
1163 format for each line of the file is:
1165 filename:lineno [module]function flags format
1167 filename : source file of the debug statement
1168 lineno : line number of the debug statement
1169 module : module that contains the debug statement
1170 function : function that contains the debug statement
1171 flags : 'p' means the line is turned 'on' for printing
1172 format : the format used for the debug statement
1176 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1177 # filename:lineno [module]function flags format
1178 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1179 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1180 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1184 // enable the message at line 1603 of file svcsock.c
1185 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1186 <debugfs>/dynamic_debug/control
1188 // enable all the messages in file svcsock.c
1189 nullarbor:~ # echo -n 'file svcsock.c +p' >
1190 <debugfs>/dynamic_debug/control
1192 // enable all the messages in the NFS server module
1193 nullarbor:~ # echo -n 'module nfsd +p' >
1194 <debugfs>/dynamic_debug/control
1196 // enable all 12 messages in the function svc_process()
1197 nullarbor:~ # echo -n 'func svc_process +p' >
1198 <debugfs>/dynamic_debug/control
1200 // disable all 12 messages in the function svc_process()
1201 nullarbor:~ # echo -n 'func svc_process -p' >
1202 <debugfs>/dynamic_debug/control
1204 See Documentation/dynamic-debug-howto.txt for additional information.
1206 config DMA_API_DEBUG
1207 bool "Enable debugging of DMA-API usage"
1208 depends on HAVE_DMA_API_DEBUG
1210 Enable this option to debug the use of the DMA API by device drivers.
1211 With this option you will be able to detect common bugs in device
1212 drivers like double-freeing of DMA mappings or freeing mappings that
1213 were never allocated.
1214 This option causes a performance degredation. Use only if you want
1215 to debug device drivers. If unsure, say N.
1217 config ATOMIC64_SELFTEST
1218 bool "Perform an atomic64_t self-test at boot"
1220 Enable this option to test the atomic64_t functions at boot.
1224 config ASYNC_RAID6_TEST
1225 tristate "Self test for hardware accelerated raid6 recovery"
1226 depends on ASYNC_RAID6_RECOV
1229 This is a one-shot self test that permutes through the
1230 recovery of all the possible two disk failure scenarios for a
1231 N-disk array. Recovery is performed with the asynchronous
1232 raid6 recovery routines, and will optionally use an offload
1233 engine if one is available.
1237 source "samples/Kconfig"
1239 source "lib/Kconfig.kgdb"
1241 source "lib/Kconfig.kmemcheck"