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"
81 debugfs is a virtual file system that kernel developers use to put
82 debugging files into. Enable this option to be able to read and
85 For detailed documentation on the debugfs API, see
86 Documentation/DocBook/filesystems.
91 bool "Run 'make headers_check' when building vmlinux"
94 This option will extract the user-visible kernel headers whenever
95 building the kernel, and will run basic sanity checks on them to
96 ensure that exported files do not attempt to include files which
97 were not exported, etc.
99 If you're making modifications to header files which are
100 relevant for userspace, say 'Y', and check the headers
101 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
102 your build tree), to make sure they're suitable.
104 config DEBUG_SECTION_MISMATCH
105 bool "Enable full Section mismatch analysis"
106 depends on UNDEFINED || (BLACKFIN)
108 # This option is on purpose disabled for now.
109 # It will be enabled when we are down to a reasonable number
110 # of section mismatch warnings (< 10 for an allyesconfig build)
112 The section mismatch analysis checks if there are illegal
113 references from one section to another section.
114 Linux will during link or during runtime drop some sections
115 and any use of code/data previously in these sections will
116 most likely result in an oops.
117 In the code functions and variables are annotated with
118 __init, __devinit etc. (see full list in include/linux/init.h)
119 which results in the code/data being placed in specific sections.
120 The section mismatch analysis is always done after a full
121 kernel build but enabling this option will in addition
123 - Add the option -fno-inline-functions-called-once to gcc
124 When inlining a function annotated __init in a non-init
125 function we would lose the section information and thus
126 the analysis would not catch the illegal reference.
127 This option tells gcc to inline less but will also
128 result in a larger kernel.
129 - Run the section mismatch analysis for each module/built-in.o
130 When we run the section mismatch analysis on vmlinux.o we
131 lose valueble information about where the mismatch was
133 Running the analysis for each module/built-in.o file
134 will tell where the mismatch happens much closer to the
135 source. The drawback is that we will report the same
136 mismatch at least twice.
137 - Enable verbose reporting from modpost to help solving
138 the section mismatches reported.
141 bool "Kernel debugging"
143 Say Y here if you are developing drivers or trying to debug and
144 identify kernel problems.
147 bool "Debug shared IRQ handlers"
148 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
150 Enable this to generate a spurious interrupt as soon as a shared
151 interrupt handler is registered, and just before one is deregistered.
152 Drivers ought to be able to handle interrupts coming in at those
153 points; some don't and need to be caught.
155 config DETECT_SOFTLOCKUP
156 bool "Detect Soft Lockups"
157 depends on DEBUG_KERNEL && !S390
160 Say Y here to enable the kernel to detect "soft lockups",
161 which are bugs that cause the kernel to loop in kernel
162 mode for more than 60 seconds, without giving other tasks a
165 When a soft-lockup is detected, the kernel will print the
166 current stack trace (which you should report), but the
167 system will stay locked up. This feature has negligible
170 (Note that "hard lockups" are separate type of bugs that
171 can be detected via the NMI-watchdog, on platforms that
174 config BOOTPARAM_SOFTLOCKUP_PANIC
175 bool "Panic (Reboot) On Soft Lockups"
176 depends on DETECT_SOFTLOCKUP
178 Say Y here to enable the kernel to panic on "soft lockups",
179 which are bugs that cause the kernel to loop in kernel
180 mode for more than 60 seconds, without giving other tasks a
183 The panic can be used in combination with panic_timeout,
184 to cause the system to reboot automatically after a
185 lockup has been detected. This feature is useful for
186 high-availability systems that have uptime guarantees and
187 where a lockup must be resolved ASAP.
191 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
193 depends on DETECT_SOFTLOCKUP
195 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
196 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
198 config DETECT_HUNG_TASK
199 bool "Detect Hung Tasks"
200 depends on DEBUG_KERNEL
201 default DETECT_SOFTLOCKUP
203 Say Y here to enable the kernel to detect "hung tasks",
204 which are bugs that cause the task to be stuck in
205 uninterruptible "D" state indefinitiley.
207 When a hung task is detected, the kernel will print the
208 current stack trace (which you should report), but the
209 task will stay in uninterruptible state. If lockdep is
210 enabled then all held locks will also be reported. This
211 feature has negligible overhead.
213 config BOOTPARAM_HUNG_TASK_PANIC
214 bool "Panic (Reboot) On Hung Tasks"
215 depends on DETECT_HUNG_TASK
217 Say Y here to enable the kernel to panic on "hung tasks",
218 which are bugs that cause the kernel to leave a task stuck
219 in uninterruptible "D" state.
221 The panic can be used in combination with panic_timeout,
222 to cause the system to reboot automatically after a
223 hung task has been detected. This feature is useful for
224 high-availability systems that have uptime guarantees and
225 where a hung tasks must be resolved ASAP.
229 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
231 depends on DETECT_HUNG_TASK
233 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
234 default 1 if BOOTPARAM_HUNG_TASK_PANIC
237 bool "Collect scheduler debugging info"
238 depends on DEBUG_KERNEL && PROC_FS
241 If you say Y here, the /proc/sched_debug file will be provided
242 that can help debug the scheduler. The runtime overhead of this
246 bool "Collect scheduler statistics"
247 depends on DEBUG_KERNEL && PROC_FS
249 If you say Y here, additional code will be inserted into the
250 scheduler and related routines to collect statistics about
251 scheduler behavior and provide them in /proc/schedstat. These
252 stats may be useful for both tuning and debugging the scheduler
253 If you aren't debugging the scheduler or trying to tune a specific
254 application, you can say N to avoid the very slight overhead
258 bool "Collect kernel timers statistics"
259 depends on DEBUG_KERNEL && PROC_FS
261 If you say Y here, additional code will be inserted into the
262 timer routines to collect statistics about kernel timers being
263 reprogrammed. The statistics can be read from /proc/timer_stats.
264 The statistics collection is started by writing 1 to /proc/timer_stats,
265 writing 0 stops it. This feature is useful to collect information
266 about timer usage patterns in kernel and userspace. This feature
267 is lightweight if enabled in the kernel config but not activated
268 (it defaults to deactivated on bootup and will only be activated
269 if some application like powertop activates it explicitly).
272 bool "Debug object operations"
273 depends on DEBUG_KERNEL
275 If you say Y here, additional code will be inserted into the
276 kernel to track the life time of various objects and validate
277 the operations on those objects.
279 config DEBUG_OBJECTS_SELFTEST
280 bool "Debug objects selftest"
281 depends on DEBUG_OBJECTS
283 This enables the selftest of the object debug code.
285 config DEBUG_OBJECTS_FREE
286 bool "Debug objects in freed memory"
287 depends on DEBUG_OBJECTS
289 This enables checks whether a k/v free operation frees an area
290 which contains an object which has not been deactivated
291 properly. This can make kmalloc/kfree-intensive workloads
294 config DEBUG_OBJECTS_TIMERS
295 bool "Debug timer objects"
296 depends on DEBUG_OBJECTS
298 If you say Y here, additional code will be inserted into the
299 timer routines to track the life time of timer objects and
300 validate the timer operations.
302 config DEBUG_OBJECTS_WORK
303 bool "Debug work objects"
304 depends on DEBUG_OBJECTS
306 If you say Y here, additional code will be inserted into the
307 work queue routines to track the life time of work objects and
308 validate the work operations.
310 config DEBUG_OBJECTS_RCU_HEAD
311 bool "Debug RCU callbacks objects"
312 depends on DEBUG_OBJECTS && PREEMPT
314 Enable this to turn on debugging of RCU list heads (call_rcu() usage).
316 config DEBUG_OBJECTS_ENABLE_DEFAULT
317 int "debug_objects bootup default value (0-1)"
320 depends on DEBUG_OBJECTS
322 Debug objects boot parameter default value
325 bool "Debug slab memory allocations"
326 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
328 Say Y here to have the kernel do limited verification on memory
329 allocation as well as poisoning memory on free to catch use of freed
330 memory. This can make kmalloc/kfree-intensive workloads much slower.
332 config DEBUG_SLAB_LEAK
333 bool "Memory leak debugging"
334 depends on DEBUG_SLAB
337 bool "SLUB debugging on by default"
338 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
341 Boot with debugging on by default. SLUB boots by default with
342 the runtime debug capabilities switched off. Enabling this is
343 equivalent to specifying the "slub_debug" parameter on boot.
344 There is no support for more fine grained debug control like
345 possible with slub_debug=xxx. SLUB debugging may be switched
346 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
351 bool "Enable SLUB performance statistics"
352 depends on SLUB && SLUB_DEBUG && SYSFS
354 SLUB statistics are useful to debug SLUBs allocation behavior in
355 order find ways to optimize the allocator. This should never be
356 enabled for production use since keeping statistics slows down
357 the allocator by a few percentage points. The slabinfo command
358 supports the determination of the most active slabs to figure
359 out which slabs are relevant to a particular load.
360 Try running: slabinfo -DA
362 config DEBUG_KMEMLEAK
363 bool "Kernel memory leak detector"
364 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
365 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE)
367 select DEBUG_FS if SYSFS
368 select STACKTRACE if STACKTRACE_SUPPORT
372 Say Y here if you want to enable the memory leak
373 detector. The memory allocation/freeing is traced in a way
374 similar to the Boehm's conservative garbage collector, the
375 difference being that the orphan objects are not freed but
376 only shown in /sys/kernel/debug/kmemleak. Enabling this
377 feature will introduce an overhead to memory
378 allocations. See Documentation/kmemleak.txt for more
381 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
382 of finding leaks due to the slab objects poisoning.
384 In order to access the kmemleak file, debugfs needs to be
385 mounted (usually at /sys/kernel/debug).
387 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
388 int "Maximum kmemleak early log entries"
389 depends on DEBUG_KMEMLEAK
393 Kmemleak must track all the memory allocations to avoid
394 reporting false positives. Since memory may be allocated or
395 freed before kmemleak is initialised, an early log buffer is
396 used to store these actions. If kmemleak reports "early log
397 buffer exceeded", please increase this value.
399 config DEBUG_KMEMLEAK_TEST
400 tristate "Simple test for the kernel memory leak detector"
401 depends on DEBUG_KMEMLEAK
403 Say Y or M here to build a test for the kernel memory leak
404 detector. This option enables a module that explicitly leaks
410 bool "Debug preemptible kernel"
411 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
414 If you say Y here then the kernel will use a debug variant of the
415 commonly used smp_processor_id() function and will print warnings
416 if kernel code uses it in a preemption-unsafe way. Also, the kernel
417 will detect preemption count underflows.
419 config DEBUG_RT_MUTEXES
420 bool "RT Mutex debugging, deadlock detection"
421 depends on DEBUG_KERNEL && RT_MUTEXES
423 This allows rt mutex semantics violations and rt mutex related
424 deadlocks (lockups) to be detected and reported automatically.
429 depends on DEBUG_RT_MUTEXES
431 config RT_MUTEX_TESTER
432 bool "Built-in scriptable tester for rt-mutexes"
433 depends on DEBUG_KERNEL && RT_MUTEXES
435 This option enables a rt-mutex tester.
437 config DEBUG_SPINLOCK
438 bool "Spinlock and rw-lock debugging: basic checks"
439 depends on DEBUG_KERNEL
441 Say Y here and build SMP to catch missing spinlock initialization
442 and certain other kinds of spinlock errors commonly made. This is
443 best used in conjunction with the NMI watchdog so that spinlock
444 deadlocks are also debuggable.
447 bool "Mutex debugging: basic checks"
448 depends on DEBUG_KERNEL
450 This feature allows mutex semantics violations to be detected and
453 config DEBUG_LOCK_ALLOC
454 bool "Lock debugging: detect incorrect freeing of live locks"
455 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
456 select DEBUG_SPINLOCK
460 This feature will check whether any held lock (spinlock, rwlock,
461 mutex or rwsem) is incorrectly freed by the kernel, via any of the
462 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
463 vfree(), etc.), whether a live lock is incorrectly reinitialized via
464 spin_lock_init()/mutex_init()/etc., or whether there is any lock
465 held during task exit.
468 bool "Lock debugging: prove locking correctness"
469 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
471 select DEBUG_SPINLOCK
473 select DEBUG_LOCK_ALLOC
476 This feature enables the kernel to prove that all locking
477 that occurs in the kernel runtime is mathematically
478 correct: that under no circumstance could an arbitrary (and
479 not yet triggered) combination of observed locking
480 sequences (on an arbitrary number of CPUs, running an
481 arbitrary number of tasks and interrupt contexts) cause a
484 In short, this feature enables the kernel to report locking
485 related deadlocks before they actually occur.
487 The proof does not depend on how hard and complex a
488 deadlock scenario would be to trigger: how many
489 participant CPUs, tasks and irq-contexts would be needed
490 for it to trigger. The proof also does not depend on
491 timing: if a race and a resulting deadlock is possible
492 theoretically (no matter how unlikely the race scenario
493 is), it will be proven so and will immediately be
494 reported by the kernel (once the event is observed that
495 makes the deadlock theoretically possible).
497 If a deadlock is impossible (i.e. the locking rules, as
498 observed by the kernel, are mathematically correct), the
499 kernel reports nothing.
501 NOTE: this feature can also be enabled for rwlocks, mutexes
502 and rwsems - in which case all dependencies between these
503 different locking variants are observed and mapped too, and
504 the proof of observed correctness is also maintained for an
505 arbitrary combination of these separate locking variants.
507 For more details, see Documentation/lockdep-design.txt.
510 bool "RCU debugging: prove RCU correctness"
511 depends on PROVE_LOCKING
514 This feature enables lockdep extensions that check for correct
515 use of RCU APIs. This is currently under development. Say Y
516 if you want to debug RCU usage or help work on the PROVE_RCU
519 Say N if you are unsure.
521 config PROVE_RCU_REPEATEDLY
522 bool "RCU debugging: don't disable PROVE_RCU on first splat"
526 By itself, PROVE_RCU will disable checking upon issuing the
527 first warning (or "splat"). This feature prevents such
528 disabling, allowing multiple RCU-lockdep warnings to be printed
531 Say N if you are unsure.
535 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
537 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
542 bool "Lock usage statistics"
543 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
545 select DEBUG_SPINLOCK
547 select DEBUG_LOCK_ALLOC
550 This feature enables tracking lock contention points
552 For more details, see Documentation/lockstat.txt
554 This also enables lock events required by "perf lock",
556 If you want to use "perf lock", you also need to turn on
557 CONFIG_EVENT_TRACING.
559 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
560 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
563 bool "Lock dependency engine debugging"
564 depends on DEBUG_KERNEL && LOCKDEP
566 If you say Y here, the lock dependency engine will do
567 additional runtime checks to debug itself, at the price
568 of more runtime overhead.
570 config TRACE_IRQFLAGS
571 depends on DEBUG_KERNEL
574 depends on TRACE_IRQFLAGS_SUPPORT
575 depends on PROVE_LOCKING
577 config DEBUG_SPINLOCK_SLEEP
578 bool "Spinlock debugging: sleep-inside-spinlock checking"
579 depends on DEBUG_KERNEL
581 If you say Y here, various routines which may sleep will become very
582 noisy if they are called with a spinlock held.
584 config DEBUG_LOCKING_API_SELFTESTS
585 bool "Locking API boot-time self-tests"
586 depends on DEBUG_KERNEL
588 Say Y here if you want the kernel to run a short self-test during
589 bootup. The self-test checks whether common types of locking bugs
590 are detected by debugging mechanisms or not. (if you disable
591 lock debugging then those bugs wont be detected of course.)
592 The following locking APIs are covered: spinlocks, rwlocks,
597 depends on STACKTRACE_SUPPORT
600 bool "kobject debugging"
601 depends on DEBUG_KERNEL
603 If you say Y here, some extra kobject debugging messages will be sent
607 bool "Highmem debugging"
608 depends on DEBUG_KERNEL && HIGHMEM
610 This options enables addition error checking for high memory systems.
611 Disable for production systems.
613 config DEBUG_BUGVERBOSE
614 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
616 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
617 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
620 Say Y here to make BUG() panics output the file name and line number
621 of the BUG call as well as the EIP and oops trace. This aids
622 debugging but costs about 70-100K of memory.
625 bool "Compile the kernel with debug info"
626 depends on DEBUG_KERNEL
628 If you say Y here the resulting kernel image will include
629 debugging info resulting in a larger kernel image.
630 This adds debug symbols to the kernel and modules (gcc -g), and
631 is needed if you intend to use kernel crashdump or binary object
632 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
633 Say Y here only if you plan to debug the kernel.
637 config DEBUG_INFO_REDUCED
638 bool "Reduce debugging information"
639 depends on DEBUG_INFO
641 If you say Y here gcc is instructed to generate less debugging
642 information for structure types. This means that tools that
643 need full debugging information (like kgdb or systemtap) won't
644 be happy. But if you merely need debugging information to
645 resolve line numbers there is no loss. Advantage is that
646 build directory object sizes shrink dramatically over a full
647 DEBUG_INFO build and compile times are reduced too.
648 Only works with newer gcc versions.
652 depends on DEBUG_KERNEL
654 Enable this to turn on extended checks in the virtual-memory system
655 that may impact performance.
660 bool "Debug VM translations"
661 depends on DEBUG_KERNEL && X86
663 Enable some costly sanity checks in virtual to page code. This can
664 catch mistakes with virt_to_page() and friends.
668 config DEBUG_NOMMU_REGIONS
669 bool "Debug the global anon/private NOMMU mapping region tree"
670 depends on DEBUG_KERNEL && !MMU
672 This option causes the global tree of anonymous and private mapping
673 regions to be regularly checked for invalid topology.
675 config DEBUG_WRITECOUNT
676 bool "Debug filesystem writers count"
677 depends on DEBUG_KERNEL
679 Enable this to catch wrong use of the writers count in struct
680 vfsmount. This will increase the size of each file struct by
685 config DEBUG_MEMORY_INIT
686 bool "Debug memory initialisation" if EMBEDDED
689 Enable this for additional checks during memory initialisation.
690 The sanity checks verify aspects of the VM such as the memory model
691 and other information provided by the architecture. Verbose
692 information will be printed at KERN_DEBUG loglevel depending
693 on the mminit_loglevel= command-line option.
698 bool "Debug linked list manipulation"
699 depends on DEBUG_KERNEL
701 Enable this to turn on extended checks in the linked-list
707 bool "Debug SG table operations"
708 depends on DEBUG_KERNEL
710 Enable this to turn on checks on scatter-gather tables. This can
711 help find problems with drivers that do not properly initialize
716 config DEBUG_NOTIFIERS
717 bool "Debug notifier call chains"
718 depends on DEBUG_KERNEL
720 Enable this to turn on sanity checking for notifier call chains.
721 This is most useful for kernel developers to make sure that
722 modules properly unregister themselves from notifier chains.
723 This is a relatively cheap check but if you care about maximum
726 config DEBUG_CREDENTIALS
727 bool "Debug credential management"
728 depends on DEBUG_KERNEL
730 Enable this to turn on some debug checking for credential
731 management. The additional code keeps track of the number of
732 pointers from task_structs to any given cred struct, and checks to
733 see that this number never exceeds the usage count of the cred
736 Furthermore, if SELinux is enabled, this also checks that the
737 security pointer in the cred struct is never seen to be invalid.
742 # Select this config option from the architecture Kconfig, if it
743 # it is preferred to always offer frame pointers as a config
744 # option on the architecture (regardless of KERNEL_DEBUG):
746 config ARCH_WANT_FRAME_POINTERS
751 bool "Compile the kernel with frame pointers"
752 depends on DEBUG_KERNEL && \
753 (CRIS || M68K || M68KNOMMU || FRV || UML || \
754 AVR32 || SUPERH || BLACKFIN || MN10300) || \
755 ARCH_WANT_FRAME_POINTERS
756 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
758 If you say Y here the resulting kernel image will be slightly
759 larger and slower, but it gives very useful debugging information
760 in case of kernel bugs. (precise oopses/stacktraces/warnings)
762 config BOOT_PRINTK_DELAY
763 bool "Delay each boot printk message by N milliseconds"
764 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
766 This build option allows you to read kernel boot messages
767 by inserting a short delay after each one. The delay is
768 specified in milliseconds on the kernel command line,
769 using "boot_delay=N".
771 It is likely that you would also need to use "lpj=M" to preset
772 the "loops per jiffie" value.
773 See a previous boot log for the "lpj" value to use for your
774 system, and then set "lpj=M" before setting "boot_delay=N".
775 NOTE: Using this option may adversely affect SMP systems.
776 I.e., processors other than the first one may not boot up.
777 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
778 what it believes to be lockup conditions.
780 config RCU_TORTURE_TEST
781 tristate "torture tests for RCU"
782 depends on DEBUG_KERNEL
785 This option provides a kernel module that runs torture tests
786 on the RCU infrastructure. The kernel module may be built
787 after the fact on the running kernel to be tested, if desired.
789 Say Y here if you want RCU torture tests to be built into
791 Say M if you want the RCU torture tests to build as a module.
792 Say N if you are unsure.
794 config RCU_TORTURE_TEST_RUNNABLE
795 bool "torture tests for RCU runnable by default"
796 depends on RCU_TORTURE_TEST = y
799 This option provides a way to build the RCU torture tests
800 directly into the kernel without them starting up at boot
801 time. You can use /proc/sys/kernel/rcutorture_runnable
802 to manually override this setting. This /proc file is
803 available only when the RCU torture tests have been built
806 Say Y here if you want the RCU torture tests to start during
807 boot (you probably don't).
808 Say N here if you want the RCU torture tests to start only
809 after being manually enabled via /proc.
811 config RCU_CPU_STALL_DETECTOR
812 bool "Check for stalled CPUs delaying RCU grace periods"
813 depends on TREE_RCU || TREE_PREEMPT_RCU
816 This option causes RCU to printk information on which
817 CPUs are delaying the current grace period, but only when
818 the grace period extends for excessive time periods.
820 Say N if you want to disable such checks.
822 Say Y if you are unsure.
824 config RCU_CPU_STALL_VERBOSE
825 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
826 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
829 This option causes RCU to printk detailed per-task information
830 for any tasks that are stalling the current RCU grace period.
832 Say N if you are unsure.
834 Say Y if you want to enable such checks.
836 config KPROBES_SANITY_TEST
837 bool "Kprobes sanity tests"
838 depends on DEBUG_KERNEL
842 This option provides for testing basic kprobes functionality on
843 boot. A sample kprobe, jprobe and kretprobe are inserted and
844 verified for functionality.
846 Say N if you are unsure.
848 config BACKTRACE_SELF_TEST
849 tristate "Self test for the backtrace code"
850 depends on DEBUG_KERNEL
853 This option provides a kernel module that can be used to test
854 the kernel stack backtrace code. This option is not useful
855 for distributions or general kernels, but only for kernel
856 developers working on architecture code.
858 Note that if you want to also test saved backtraces, you will
859 have to enable STACKTRACE as well.
861 Say N if you are unsure.
863 config DEBUG_BLOCK_EXT_DEVT
864 bool "Force extended block device numbers and spread them"
865 depends on DEBUG_KERNEL
869 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
870 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
871 YOU ARE DOING. Distros, please enable this and fix whatever
874 Conventionally, block device numbers are allocated from
875 predetermined contiguous area. However, extended block area
876 may introduce non-contiguous block device numbers. This
877 option forces most block device numbers to be allocated from
878 the extended space and spreads them to discover kernel or
879 userland code paths which assume predetermined contiguous
880 device number allocation.
882 Note that turning on this debug option shuffles all the
883 device numbers for all IDE and SCSI devices including libata
884 ones, so root partition specified using device number
885 directly (via rdev or root=MAJ:MIN) won't work anymore.
886 Textual device names (root=/dev/sdXn) will continue to work.
888 Say N if you are unsure.
890 config DEBUG_FORCE_WEAK_PER_CPU
891 bool "Force weak per-cpu definitions"
892 depends on DEBUG_KERNEL
894 s390 and alpha require percpu variables in modules to be
895 defined weak to work around addressing range issue which
896 puts the following two restrictions on percpu variable
899 1. percpu symbols must be unique whether static or not
900 2. percpu variables can't be defined inside a function
902 To ensure that generic code follows the above rules, this
903 option forces all percpu variables to be defined as weak.
906 tristate "Linux Kernel Dump Test Tool Module"
911 This module enables testing of the different dumping mechanisms by
912 inducing system failures at predefined crash points.
913 If you don't need it: say N
914 Choose M here to compile this code as a module. The module will be
917 Documentation on how to use the module can be found in
918 Documentation/fault-injection/provoke-crashes.txt
920 config CPU_NOTIFIER_ERROR_INJECT
921 tristate "CPU notifier error injection module"
922 depends on HOTPLUG_CPU && DEBUG_KERNEL
924 This option provides a kernel module that can be used to test
925 the error handling of the cpu notifiers
927 To compile this code as a module, choose M here: the module will
928 be called cpu-notifier-error-inject.
932 config FAULT_INJECTION
933 bool "Fault-injection framework"
934 depends on DEBUG_KERNEL
936 Provide fault-injection framework.
937 For more details, see Documentation/fault-injection/.
940 bool "Fault-injection capability for kmalloc"
941 depends on FAULT_INJECTION
942 depends on SLAB || SLUB
944 Provide fault-injection capability for kmalloc.
946 config FAIL_PAGE_ALLOC
947 bool "Fault-injection capabilitiy for alloc_pages()"
948 depends on FAULT_INJECTION
950 Provide fault-injection capability for alloc_pages().
952 config FAIL_MAKE_REQUEST
953 bool "Fault-injection capability for disk IO"
954 depends on FAULT_INJECTION && BLOCK
956 Provide fault-injection capability for disk IO.
958 config FAIL_IO_TIMEOUT
959 bool "Fault-injection capability for faking disk interrupts"
960 depends on FAULT_INJECTION && BLOCK
962 Provide fault-injection capability on end IO handling. This
963 will make the block layer "forget" an interrupt as configured,
964 thus exercising the error handling.
966 Only works with drivers that use the generic timeout handling,
967 for others it wont do anything.
969 config FAULT_INJECTION_DEBUG_FS
970 bool "Debugfs entries for fault-injection capabilities"
971 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
973 Enable configuration of fault-injection capabilities via debugfs.
975 config FAULT_INJECTION_STACKTRACE_FILTER
976 bool "stacktrace filter for fault-injection capabilities"
977 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
980 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE
982 Provide stacktrace filter for fault-injection capabilities
985 bool "Latency measuring infrastructure"
986 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE
992 depends on HAVE_LATENCYTOP_SUPPORT
994 Enable this option if you want to use the LatencyTOP tool
995 to find out which userspace is blocking on what kernel operations.
997 config SYSCTL_SYSCALL_CHECK
1001 sys_sysctl uses binary paths that have been found challenging
1002 to properly maintain and use. This enables checks that help
1003 you to keep things correct.
1005 source mm/Kconfig.debug
1006 source kernel/trace/Kconfig
1008 config PROVIDE_OHCI1394_DMA_INIT
1009 bool "Remote debugging over FireWire early on boot"
1010 depends on PCI && X86
1012 If you want to debug problems which hang or crash the kernel early
1013 on boot and the crashing machine has a FireWire port, you can use
1014 this feature to remotely access the memory of the crashed machine
1015 over FireWire. This employs remote DMA as part of the OHCI1394
1016 specification which is now the standard for FireWire controllers.
1018 With remote DMA, you can monitor the printk buffer remotely using
1019 firescope and access all memory below 4GB using fireproxy from gdb.
1020 Even controlling a kernel debugger is possible using remote DMA.
1024 If ohci1394_dma=early is used as boot parameter, it will initialize
1025 all OHCI1394 controllers which are found in the PCI config space.
1027 As all changes to the FireWire bus such as enabling and disabling
1028 devices cause a bus reset and thereby disable remote DMA for all
1029 devices, be sure to have the cable plugged and FireWire enabled on
1030 the debugging host before booting the debug target for debugging.
1032 This code (~1k) is freed after boot. By then, the firewire stack
1033 in charge of the OHCI-1394 controllers should be used instead.
1035 See Documentation/debugging-via-ohci1394.txt for more information.
1037 config FIREWIRE_OHCI_REMOTE_DMA
1038 bool "Remote debugging over FireWire with firewire-ohci"
1039 depends on FIREWIRE_OHCI
1041 This option lets you use the FireWire bus for remote debugging
1042 with help of the firewire-ohci driver. It enables unfiltered
1043 remote DMA in firewire-ohci.
1044 See Documentation/debugging-via-ohci1394.txt for more information.
1049 bool "Build targets in Documentation/ tree"
1050 depends on HEADERS_CHECK
1052 This option attempts to build objects from the source files in the
1053 kernel Documentation/ tree.
1055 Say N if you are unsure.
1057 config DYNAMIC_DEBUG
1058 bool "Enable dynamic printk() support"
1064 Compiles debug level messages into the kernel, which would not
1065 otherwise be available at runtime. These messages can then be
1066 enabled/disabled based on various levels of scope - per source file,
1067 function, module, format string, and line number. This mechanism
1068 implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1069 this compile option is a larger kernel text size of about 2%.
1073 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1074 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1075 filesystem must first be mounted before making use of this feature.
1076 We refer the control file as: <debugfs>/dynamic_debug/control. This
1077 file contains a list of the debug statements that can be enabled. The
1078 format for each line of the file is:
1080 filename:lineno [module]function flags format
1082 filename : source file of the debug statement
1083 lineno : line number of the debug statement
1084 module : module that contains the debug statement
1085 function : function that contains the debug statement
1086 flags : 'p' means the line is turned 'on' for printing
1087 format : the format used for the debug statement
1091 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1092 # filename:lineno [module]function flags format
1093 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1094 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1095 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1099 // enable the message at line 1603 of file svcsock.c
1100 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1101 <debugfs>/dynamic_debug/control
1103 // enable all the messages in file svcsock.c
1104 nullarbor:~ # echo -n 'file svcsock.c +p' >
1105 <debugfs>/dynamic_debug/control
1107 // enable all the messages in the NFS server module
1108 nullarbor:~ # echo -n 'module nfsd +p' >
1109 <debugfs>/dynamic_debug/control
1111 // enable all 12 messages in the function svc_process()
1112 nullarbor:~ # echo -n 'func svc_process +p' >
1113 <debugfs>/dynamic_debug/control
1115 // disable all 12 messages in the function svc_process()
1116 nullarbor:~ # echo -n 'func svc_process -p' >
1117 <debugfs>/dynamic_debug/control
1119 See Documentation/dynamic-debug-howto.txt for additional information.
1121 config DMA_API_DEBUG
1122 bool "Enable debugging of DMA-API usage"
1123 depends on HAVE_DMA_API_DEBUG
1125 Enable this option to debug the use of the DMA API by device drivers.
1126 With this option you will be able to detect common bugs in device
1127 drivers like double-freeing of DMA mappings or freeing mappings that
1128 were never allocated.
1129 This option causes a performance degredation. Use only if you want
1130 to debug device drivers. If unsure, say N.
1132 config ATOMIC64_SELFTEST
1133 bool "Perform an atomic64_t self-test at boot"
1135 Enable this option to test the atomic64_t functions at boot.
1139 source "samples/Kconfig"
1141 source "lib/Kconfig.kgdb"
1143 source "lib/Kconfig.kmemcheck"