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 LOCKUP_DETECTOR
156 bool "Detect Hard and Soft Lockups"
157 depends on DEBUG_KERNEL && !S390
159 Say Y here to enable the kernel to act as a watchdog to detect
160 hard and soft lockups.
162 Softlockups are bugs that cause the kernel to loop in kernel
163 mode for more than 60 seconds, without giving other tasks a
164 chance to run. The current stack trace is displayed upon
165 detection and the system will stay locked up.
167 Hardlockups are bugs that cause the CPU to loop in kernel mode
168 for more than 60 seconds, without letting other interrupts have a
169 chance to run. The current stack trace is displayed upon detection
170 and the system will stay locked up.
172 The overhead should be minimal. A periodic hrtimer runs to
173 generate interrupts and kick the watchdog task every 10-12 seconds.
174 An NMI is generated every 60 seconds or so to check for hardlockups.
176 config HARDLOCKUP_DETECTOR
177 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI
179 config BOOTPARAM_SOFTLOCKUP_PANIC
180 bool "Panic (Reboot) On Soft Lockups"
181 depends on LOCKUP_DETECTOR
183 Say Y here to enable the kernel to panic on "soft lockups",
184 which are bugs that cause the kernel to loop in kernel
185 mode for more than 60 seconds, without giving other tasks a
188 The panic can be used in combination with panic_timeout,
189 to cause the system to reboot automatically after a
190 lockup has been detected. This feature is useful for
191 high-availability systems that have uptime guarantees and
192 where a lockup must be resolved ASAP.
196 config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
198 depends on LOCKUP_DETECTOR
200 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
201 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
203 config DETECT_HUNG_TASK
204 bool "Detect Hung Tasks"
205 depends on DEBUG_KERNEL
206 default DETECT_SOFTLOCKUP
208 Say Y here to enable the kernel to detect "hung tasks",
209 which are bugs that cause the task to be stuck in
210 uninterruptible "D" state indefinitiley.
212 When a hung task is detected, the kernel will print the
213 current stack trace (which you should report), but the
214 task will stay in uninterruptible state. If lockdep is
215 enabled then all held locks will also be reported. This
216 feature has negligible overhead.
218 config BOOTPARAM_HUNG_TASK_PANIC
219 bool "Panic (Reboot) On Hung Tasks"
220 depends on DETECT_HUNG_TASK
222 Say Y here to enable the kernel to panic on "hung tasks",
223 which are bugs that cause the kernel to leave a task stuck
224 in uninterruptible "D" state.
226 The panic can be used in combination with panic_timeout,
227 to cause the system to reboot automatically after a
228 hung task has been detected. This feature is useful for
229 high-availability systems that have uptime guarantees and
230 where a hung tasks must be resolved ASAP.
234 config BOOTPARAM_HUNG_TASK_PANIC_VALUE
236 depends on DETECT_HUNG_TASK
238 default 0 if !BOOTPARAM_HUNG_TASK_PANIC
239 default 1 if BOOTPARAM_HUNG_TASK_PANIC
242 bool "Collect scheduler debugging info"
243 depends on DEBUG_KERNEL && PROC_FS
246 If you say Y here, the /proc/sched_debug file will be provided
247 that can help debug the scheduler. The runtime overhead of this
251 bool "Collect scheduler statistics"
252 depends on DEBUG_KERNEL && PROC_FS
254 If you say Y here, additional code will be inserted into the
255 scheduler and related routines to collect statistics about
256 scheduler behavior and provide them in /proc/schedstat. These
257 stats may be useful for both tuning and debugging the scheduler
258 If you aren't debugging the scheduler or trying to tune a specific
259 application, you can say N to avoid the very slight overhead
263 bool "Collect kernel timers statistics"
264 depends on DEBUG_KERNEL && PROC_FS
266 If you say Y here, additional code will be inserted into the
267 timer routines to collect statistics about kernel timers being
268 reprogrammed. The statistics can be read from /proc/timer_stats.
269 The statistics collection is started by writing 1 to /proc/timer_stats,
270 writing 0 stops it. This feature is useful to collect information
271 about timer usage patterns in kernel and userspace. This feature
272 is lightweight if enabled in the kernel config but not activated
273 (it defaults to deactivated on bootup and will only be activated
274 if some application like powertop activates it explicitly).
277 bool "Debug object operations"
278 depends on DEBUG_KERNEL
280 If you say Y here, additional code will be inserted into the
281 kernel to track the life time of various objects and validate
282 the operations on those objects.
284 config DEBUG_OBJECTS_SELFTEST
285 bool "Debug objects selftest"
286 depends on DEBUG_OBJECTS
288 This enables the selftest of the object debug code.
290 config DEBUG_OBJECTS_FREE
291 bool "Debug objects in freed memory"
292 depends on DEBUG_OBJECTS
294 This enables checks whether a k/v free operation frees an area
295 which contains an object which has not been deactivated
296 properly. This can make kmalloc/kfree-intensive workloads
299 config DEBUG_OBJECTS_TIMERS
300 bool "Debug timer objects"
301 depends on DEBUG_OBJECTS
303 If you say Y here, additional code will be inserted into the
304 timer routines to track the life time of timer objects and
305 validate the timer operations.
307 config DEBUG_OBJECTS_WORK
308 bool "Debug work objects"
309 depends on DEBUG_OBJECTS
311 If you say Y here, additional code will be inserted into the
312 work queue routines to track the life time of work objects and
313 validate the work operations.
315 config DEBUG_OBJECTS_ENABLE_DEFAULT
316 int "debug_objects bootup default value (0-1)"
319 depends on DEBUG_OBJECTS
321 Debug objects boot parameter default value
324 bool "Debug slab memory allocations"
325 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
327 Say Y here to have the kernel do limited verification on memory
328 allocation as well as poisoning memory on free to catch use of freed
329 memory. This can make kmalloc/kfree-intensive workloads much slower.
331 config DEBUG_SLAB_LEAK
332 bool "Memory leak debugging"
333 depends on DEBUG_SLAB
336 bool "SLUB debugging on by default"
337 depends on SLUB && SLUB_DEBUG && !KMEMCHECK
340 Boot with debugging on by default. SLUB boots by default with
341 the runtime debug capabilities switched off. Enabling this is
342 equivalent to specifying the "slub_debug" parameter on boot.
343 There is no support for more fine grained debug control like
344 possible with slub_debug=xxx. SLUB debugging may be switched
345 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
350 bool "Enable SLUB performance statistics"
351 depends on SLUB && SLUB_DEBUG && SYSFS
353 SLUB statistics are useful to debug SLUBs allocation behavior in
354 order find ways to optimize the allocator. This should never be
355 enabled for production use since keeping statistics slows down
356 the allocator by a few percentage points. The slabinfo command
357 supports the determination of the most active slabs to figure
358 out which slabs are relevant to a particular load.
359 Try running: slabinfo -DA
361 config DEBUG_KMEMLEAK
362 bool "Kernel memory leak detector"
363 depends on DEBUG_KERNEL && EXPERIMENTAL && !MEMORY_HOTPLUG && \
364 (X86 || ARM || PPC || S390 || SPARC64 || SUPERH || MICROBLAZE)
366 select DEBUG_FS if SYSFS
367 select STACKTRACE if STACKTRACE_SUPPORT
371 Say Y here if you want to enable the memory leak
372 detector. The memory allocation/freeing is traced in a way
373 similar to the Boehm's conservative garbage collector, the
374 difference being that the orphan objects are not freed but
375 only shown in /sys/kernel/debug/kmemleak. Enabling this
376 feature will introduce an overhead to memory
377 allocations. See Documentation/kmemleak.txt for more
380 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
381 of finding leaks due to the slab objects poisoning.
383 In order to access the kmemleak file, debugfs needs to be
384 mounted (usually at /sys/kernel/debug).
386 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
387 int "Maximum kmemleak early log entries"
388 depends on DEBUG_KMEMLEAK
392 Kmemleak must track all the memory allocations to avoid
393 reporting false positives. Since memory may be allocated or
394 freed before kmemleak is initialised, an early log buffer is
395 used to store these actions. If kmemleak reports "early log
396 buffer exceeded", please increase this value.
398 config DEBUG_KMEMLEAK_TEST
399 tristate "Simple test for the kernel memory leak detector"
400 depends on DEBUG_KMEMLEAK
402 Say Y or M here to build a test for the kernel memory leak
403 detector. This option enables a module that explicitly leaks
409 bool "Debug preemptible kernel"
410 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
413 If you say Y here then the kernel will use a debug variant of the
414 commonly used smp_processor_id() function and will print warnings
415 if kernel code uses it in a preemption-unsafe way. Also, the kernel
416 will detect preemption count underflows.
418 config DEBUG_RT_MUTEXES
419 bool "RT Mutex debugging, deadlock detection"
420 depends on DEBUG_KERNEL && RT_MUTEXES
422 This allows rt mutex semantics violations and rt mutex related
423 deadlocks (lockups) to be detected and reported automatically.
428 depends on DEBUG_RT_MUTEXES
430 config RT_MUTEX_TESTER
431 bool "Built-in scriptable tester for rt-mutexes"
432 depends on DEBUG_KERNEL && RT_MUTEXES
434 This option enables a rt-mutex tester.
436 config DEBUG_SPINLOCK
437 bool "Spinlock and rw-lock debugging: basic checks"
438 depends on DEBUG_KERNEL
440 Say Y here and build SMP to catch missing spinlock initialization
441 and certain other kinds of spinlock errors commonly made. This is
442 best used in conjunction with the NMI watchdog so that spinlock
443 deadlocks are also debuggable.
446 bool "Mutex debugging: basic checks"
447 depends on DEBUG_KERNEL
449 This feature allows mutex semantics violations to be detected and
452 config DEBUG_LOCK_ALLOC
453 bool "Lock debugging: detect incorrect freeing of live locks"
454 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
455 select DEBUG_SPINLOCK
459 This feature will check whether any held lock (spinlock, rwlock,
460 mutex or rwsem) is incorrectly freed by the kernel, via any of the
461 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
462 vfree(), etc.), whether a live lock is incorrectly reinitialized via
463 spin_lock_init()/mutex_init()/etc., or whether there is any lock
464 held during task exit.
467 bool "Lock debugging: prove locking correctness"
468 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
470 select DEBUG_SPINLOCK
472 select DEBUG_LOCK_ALLOC
475 This feature enables the kernel to prove that all locking
476 that occurs in the kernel runtime is mathematically
477 correct: that under no circumstance could an arbitrary (and
478 not yet triggered) combination of observed locking
479 sequences (on an arbitrary number of CPUs, running an
480 arbitrary number of tasks and interrupt contexts) cause a
483 In short, this feature enables the kernel to report locking
484 related deadlocks before they actually occur.
486 The proof does not depend on how hard and complex a
487 deadlock scenario would be to trigger: how many
488 participant CPUs, tasks and irq-contexts would be needed
489 for it to trigger. The proof also does not depend on
490 timing: if a race and a resulting deadlock is possible
491 theoretically (no matter how unlikely the race scenario
492 is), it will be proven so and will immediately be
493 reported by the kernel (once the event is observed that
494 makes the deadlock theoretically possible).
496 If a deadlock is impossible (i.e. the locking rules, as
497 observed by the kernel, are mathematically correct), the
498 kernel reports nothing.
500 NOTE: this feature can also be enabled for rwlocks, mutexes
501 and rwsems - in which case all dependencies between these
502 different locking variants are observed and mapped too, and
503 the proof of observed correctness is also maintained for an
504 arbitrary combination of these separate locking variants.
506 For more details, see Documentation/lockdep-design.txt.
509 bool "RCU debugging: prove RCU correctness"
510 depends on PROVE_LOCKING
513 This feature enables lockdep extensions that check for correct
514 use of RCU APIs. This is currently under development. Say Y
515 if you want to debug RCU usage or help work on the PROVE_RCU
518 Say N if you are unsure.
520 config PROVE_RCU_REPEATEDLY
521 bool "RCU debugging: don't disable PROVE_RCU on first splat"
525 By itself, PROVE_RCU will disable checking upon issuing the
526 first warning (or "splat"). This feature prevents such
527 disabling, allowing multiple RCU-lockdep warnings to be printed
530 Say N if you are unsure.
534 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
536 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390
541 bool "Lock usage statistics"
542 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
544 select DEBUG_SPINLOCK
546 select DEBUG_LOCK_ALLOC
549 This feature enables tracking lock contention points
551 For more details, see Documentation/lockstat.txt
553 This also enables lock events required by "perf lock",
555 If you want to use "perf lock", you also need to turn on
556 CONFIG_EVENT_TRACING.
558 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
559 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
562 bool "Lock dependency engine debugging"
563 depends on DEBUG_KERNEL && LOCKDEP
565 If you say Y here, the lock dependency engine will do
566 additional runtime checks to debug itself, at the price
567 of more runtime overhead.
569 config TRACE_IRQFLAGS
570 depends on DEBUG_KERNEL
573 depends on TRACE_IRQFLAGS_SUPPORT
574 depends on PROVE_LOCKING
576 config DEBUG_SPINLOCK_SLEEP
577 bool "Spinlock debugging: sleep-inside-spinlock checking"
578 depends on DEBUG_KERNEL
580 If you say Y here, various routines which may sleep will become very
581 noisy if they are called with a spinlock held.
583 config DEBUG_LOCKING_API_SELFTESTS
584 bool "Locking API boot-time self-tests"
585 depends on DEBUG_KERNEL
587 Say Y here if you want the kernel to run a short self-test during
588 bootup. The self-test checks whether common types of locking bugs
589 are detected by debugging mechanisms or not. (if you disable
590 lock debugging then those bugs wont be detected of course.)
591 The following locking APIs are covered: spinlocks, rwlocks,
596 depends on STACKTRACE_SUPPORT
599 bool "kobject debugging"
600 depends on DEBUG_KERNEL
602 If you say Y here, some extra kobject debugging messages will be sent
606 bool "Highmem debugging"
607 depends on DEBUG_KERNEL && HIGHMEM
609 This options enables addition error checking for high memory systems.
610 Disable for production systems.
612 config DEBUG_BUGVERBOSE
613 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
615 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \
616 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300
619 Say Y here to make BUG() panics output the file name and line number
620 of the BUG call as well as the EIP and oops trace. This aids
621 debugging but costs about 70-100K of memory.
624 bool "Compile the kernel with debug info"
625 depends on DEBUG_KERNEL
627 If you say Y here the resulting kernel image will include
628 debugging info resulting in a larger kernel image.
629 This adds debug symbols to the kernel and modules (gcc -g), and
630 is needed if you intend to use kernel crashdump or binary object
631 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
632 Say Y here only if you plan to debug the kernel.
638 depends on DEBUG_KERNEL
640 Enable this to turn on extended checks in the virtual-memory system
641 that may impact performance.
646 bool "Debug VM translations"
647 depends on DEBUG_KERNEL && X86
649 Enable some costly sanity checks in virtual to page code. This can
650 catch mistakes with virt_to_page() and friends.
654 config DEBUG_NOMMU_REGIONS
655 bool "Debug the global anon/private NOMMU mapping region tree"
656 depends on DEBUG_KERNEL && !MMU
658 This option causes the global tree of anonymous and private mapping
659 regions to be regularly checked for invalid topology.
661 config DEBUG_WRITECOUNT
662 bool "Debug filesystem writers count"
663 depends on DEBUG_KERNEL
665 Enable this to catch wrong use of the writers count in struct
666 vfsmount. This will increase the size of each file struct by
671 config DEBUG_MEMORY_INIT
672 bool "Debug memory initialisation" if EMBEDDED
675 Enable this for additional checks during memory initialisation.
676 The sanity checks verify aspects of the VM such as the memory model
677 and other information provided by the architecture. Verbose
678 information will be printed at KERN_DEBUG loglevel depending
679 on the mminit_loglevel= command-line option.
684 bool "Debug linked list manipulation"
685 depends on DEBUG_KERNEL
687 Enable this to turn on extended checks in the linked-list
693 bool "Debug SG table operations"
694 depends on DEBUG_KERNEL
696 Enable this to turn on checks on scatter-gather tables. This can
697 help find problems with drivers that do not properly initialize
702 config DEBUG_NOTIFIERS
703 bool "Debug notifier call chains"
704 depends on DEBUG_KERNEL
706 Enable this to turn on sanity checking for notifier call chains.
707 This is most useful for kernel developers to make sure that
708 modules properly unregister themselves from notifier chains.
709 This is a relatively cheap check but if you care about maximum
712 config DEBUG_CREDENTIALS
713 bool "Debug credential management"
714 depends on DEBUG_KERNEL
716 Enable this to turn on some debug checking for credential
717 management. The additional code keeps track of the number of
718 pointers from task_structs to any given cred struct, and checks to
719 see that this number never exceeds the usage count of the cred
722 Furthermore, if SELinux is enabled, this also checks that the
723 security pointer in the cred struct is never seen to be invalid.
728 # Select this config option from the architecture Kconfig, if it
729 # it is preferred to always offer frame pointers as a config
730 # option on the architecture (regardless of KERNEL_DEBUG):
732 config ARCH_WANT_FRAME_POINTERS
737 bool "Compile the kernel with frame pointers"
738 depends on DEBUG_KERNEL && \
739 (CRIS || M68K || M68KNOMMU || FRV || UML || \
740 AVR32 || SUPERH || BLACKFIN || MN10300) || \
741 ARCH_WANT_FRAME_POINTERS
742 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
744 If you say Y here the resulting kernel image will be slightly
745 larger and slower, but it gives very useful debugging information
746 in case of kernel bugs. (precise oopses/stacktraces/warnings)
748 config BOOT_PRINTK_DELAY
749 bool "Delay each boot printk message by N milliseconds"
750 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
752 This build option allows you to read kernel boot messages
753 by inserting a short delay after each one. The delay is
754 specified in milliseconds on the kernel command line,
755 using "boot_delay=N".
757 It is likely that you would also need to use "lpj=M" to preset
758 the "loops per jiffie" value.
759 See a previous boot log for the "lpj" value to use for your
760 system, and then set "lpj=M" before setting "boot_delay=N".
761 NOTE: Using this option may adversely affect SMP systems.
762 I.e., processors other than the first one may not boot up.
763 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
764 what it believes to be lockup conditions.
766 config RCU_TORTURE_TEST
767 tristate "torture tests for RCU"
768 depends on DEBUG_KERNEL
771 This option provides a kernel module that runs torture tests
772 on the RCU infrastructure. The kernel module may be built
773 after the fact on the running kernel to be tested, if desired.
775 Say Y here if you want RCU torture tests to be built into
777 Say M if you want the RCU torture tests to build as a module.
778 Say N if you are unsure.
780 config RCU_TORTURE_TEST_RUNNABLE
781 bool "torture tests for RCU runnable by default"
782 depends on RCU_TORTURE_TEST = y
785 This option provides a way to build the RCU torture tests
786 directly into the kernel without them starting up at boot
787 time. You can use /proc/sys/kernel/rcutorture_runnable
788 to manually override this setting. This /proc file is
789 available only when the RCU torture tests have been built
792 Say Y here if you want the RCU torture tests to start during
793 boot (you probably don't).
794 Say N here if you want the RCU torture tests to start only
795 after being manually enabled via /proc.
797 config RCU_CPU_STALL_DETECTOR
798 bool "Check for stalled CPUs delaying RCU grace periods"
799 depends on TREE_RCU || TREE_PREEMPT_RCU
802 This option causes RCU to printk information on which
803 CPUs are delaying the current grace period, but only when
804 the grace period extends for excessive time periods.
806 Say N if you want to disable such checks.
808 Say Y if you are unsure.
810 config RCU_CPU_STALL_VERBOSE
811 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
812 depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU
815 This option causes RCU to printk detailed per-task information
816 for any tasks that are stalling the current RCU grace period.
818 Say N if you are unsure.
820 Say Y if you want to enable such checks.
822 config KPROBES_SANITY_TEST
823 bool "Kprobes sanity tests"
824 depends on DEBUG_KERNEL
828 This option provides for testing basic kprobes functionality on
829 boot. A sample kprobe, jprobe and kretprobe are inserted and
830 verified for functionality.
832 Say N if you are unsure.
834 config BACKTRACE_SELF_TEST
835 tristate "Self test for the backtrace code"
836 depends on DEBUG_KERNEL
839 This option provides a kernel module that can be used to test
840 the kernel stack backtrace code. This option is not useful
841 for distributions or general kernels, but only for kernel
842 developers working on architecture code.
844 Note that if you want to also test saved backtraces, you will
845 have to enable STACKTRACE as well.
847 Say N if you are unsure.
849 config DEBUG_BLOCK_EXT_DEVT
850 bool "Force extended block device numbers and spread them"
851 depends on DEBUG_KERNEL
855 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
856 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
857 YOU ARE DOING. Distros, please enable this and fix whatever
860 Conventionally, block device numbers are allocated from
861 predetermined contiguous area. However, extended block area
862 may introduce non-contiguous block device numbers. This
863 option forces most block device numbers to be allocated from
864 the extended space and spreads them to discover kernel or
865 userland code paths which assume predetermined contiguous
866 device number allocation.
868 Note that turning on this debug option shuffles all the
869 device numbers for all IDE and SCSI devices including libata
870 ones, so root partition specified using device number
871 directly (via rdev or root=MAJ:MIN) won't work anymore.
872 Textual device names (root=/dev/sdXn) will continue to work.
874 Say N if you are unsure.
876 config DEBUG_FORCE_WEAK_PER_CPU
877 bool "Force weak per-cpu definitions"
878 depends on DEBUG_KERNEL
880 s390 and alpha require percpu variables in modules to be
881 defined weak to work around addressing range issue which
882 puts the following two restrictions on percpu variable
885 1. percpu symbols must be unique whether static or not
886 2. percpu variables can't be defined inside a function
888 To ensure that generic code follows the above rules, this
889 option forces all percpu variables to be defined as weak.
892 tristate "Linux Kernel Dump Test Tool Module"
897 This module enables testing of the different dumping mechanisms by
898 inducing system failures at predefined crash points.
899 If you don't need it: say N
900 Choose M here to compile this code as a module. The module will be
903 Documentation on how to use the module can be found in
904 Documentation/fault-injection/provoke-crashes.txt
906 config CPU_NOTIFIER_ERROR_INJECT
907 tristate "CPU notifier error injection module"
908 depends on HOTPLUG_CPU && DEBUG_KERNEL
910 This option provides a kernel module that can be used to test
911 the error handling of the cpu notifiers
913 To compile this code as a module, choose M here: the module will
914 be called cpu-notifier-error-inject.
918 config FAULT_INJECTION
919 bool "Fault-injection framework"
920 depends on DEBUG_KERNEL
922 Provide fault-injection framework.
923 For more details, see Documentation/fault-injection/.
926 bool "Fault-injection capability for kmalloc"
927 depends on FAULT_INJECTION
928 depends on SLAB || SLUB
930 Provide fault-injection capability for kmalloc.
932 config FAIL_PAGE_ALLOC
933 bool "Fault-injection capabilitiy for alloc_pages()"
934 depends on FAULT_INJECTION
936 Provide fault-injection capability for alloc_pages().
938 config FAIL_MAKE_REQUEST
939 bool "Fault-injection capability for disk IO"
940 depends on FAULT_INJECTION && BLOCK
942 Provide fault-injection capability for disk IO.
944 config FAIL_IO_TIMEOUT
945 bool "Faul-injection capability for faking disk interrupts"
946 depends on FAULT_INJECTION && BLOCK
948 Provide fault-injection capability on end IO handling. This
949 will make the block layer "forget" an interrupt as configured,
950 thus exercising the error handling.
952 Only works with drivers that use the generic timeout handling,
953 for others it wont do anything.
955 config FAULT_INJECTION_DEBUG_FS
956 bool "Debugfs entries for fault-injection capabilities"
957 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
959 Enable configuration of fault-injection capabilities via debugfs.
961 config FAULT_INJECTION_STACKTRACE_FILTER
962 bool "stacktrace filter for fault-injection capabilities"
963 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
966 select FRAME_POINTER if !PPC && !S390
968 Provide stacktrace filter for fault-injection capabilities
971 bool "Latency measuring infrastructure"
972 select FRAME_POINTER if !MIPS && !PPC && !S390
978 depends on HAVE_LATENCYTOP_SUPPORT
980 Enable this option if you want to use the LatencyTOP tool
981 to find out which userspace is blocking on what kernel operations.
983 config SYSCTL_SYSCALL_CHECK
987 sys_sysctl uses binary paths that have been found challenging
988 to properly maintain and use. This enables checks that help
989 you to keep things correct.
991 source mm/Kconfig.debug
992 source kernel/trace/Kconfig
994 config PROVIDE_OHCI1394_DMA_INIT
995 bool "Remote debugging over FireWire early on boot"
996 depends on PCI && X86
998 If you want to debug problems which hang or crash the kernel early
999 on boot and the crashing machine has a FireWire port, you can use
1000 this feature to remotely access the memory of the crashed machine
1001 over FireWire. This employs remote DMA as part of the OHCI1394
1002 specification which is now the standard for FireWire controllers.
1004 With remote DMA, you can monitor the printk buffer remotely using
1005 firescope and access all memory below 4GB using fireproxy from gdb.
1006 Even controlling a kernel debugger is possible using remote DMA.
1010 If ohci1394_dma=early is used as boot parameter, it will initialize
1011 all OHCI1394 controllers which are found in the PCI config space.
1013 As all changes to the FireWire bus such as enabling and disabling
1014 devices cause a bus reset and thereby disable remote DMA for all
1015 devices, be sure to have the cable plugged and FireWire enabled on
1016 the debugging host before booting the debug target for debugging.
1018 This code (~1k) is freed after boot. By then, the firewire stack
1019 in charge of the OHCI-1394 controllers should be used instead.
1021 See Documentation/debugging-via-ohci1394.txt for more information.
1023 config FIREWIRE_OHCI_REMOTE_DMA
1024 bool "Remote debugging over FireWire with firewire-ohci"
1025 depends on FIREWIRE_OHCI
1027 This option lets you use the FireWire bus for remote debugging
1028 with help of the firewire-ohci driver. It enables unfiltered
1029 remote DMA in firewire-ohci.
1030 See Documentation/debugging-via-ohci1394.txt for more information.
1035 bool "Build targets in Documentation/ tree"
1036 depends on HEADERS_CHECK
1038 This option attempts to build objects from the source files in the
1039 kernel Documentation/ tree.
1041 Say N if you are unsure.
1043 config DYNAMIC_DEBUG
1044 bool "Enable dynamic printk() support"
1050 Compiles debug level messages into the kernel, which would not
1051 otherwise be available at runtime. These messages can then be
1052 enabled/disabled based on various levels of scope - per source file,
1053 function, module, format string, and line number. This mechanism
1054 implicitly enables all pr_debug() and dev_dbg() calls. The impact of
1055 this compile option is a larger kernel text size of about 2%.
1059 Dynamic debugging is controlled via the 'dynamic_debug/control' file,
1060 which is contained in the 'debugfs' filesystem. Thus, the debugfs
1061 filesystem must first be mounted before making use of this feature.
1062 We refer the control file as: <debugfs>/dynamic_debug/control. This
1063 file contains a list of the debug statements that can be enabled. The
1064 format for each line of the file is:
1066 filename:lineno [module]function flags format
1068 filename : source file of the debug statement
1069 lineno : line number of the debug statement
1070 module : module that contains the debug statement
1071 function : function that contains the debug statement
1072 flags : 'p' means the line is turned 'on' for printing
1073 format : the format used for the debug statement
1077 nullarbor:~ # cat <debugfs>/dynamic_debug/control
1078 # filename:lineno [module]function flags format
1079 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012"
1080 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012"
1081 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012"
1085 // enable the message at line 1603 of file svcsock.c
1086 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
1087 <debugfs>/dynamic_debug/control
1089 // enable all the messages in file svcsock.c
1090 nullarbor:~ # echo -n 'file svcsock.c +p' >
1091 <debugfs>/dynamic_debug/control
1093 // enable all the messages in the NFS server module
1094 nullarbor:~ # echo -n 'module nfsd +p' >
1095 <debugfs>/dynamic_debug/control
1097 // enable all 12 messages in the function svc_process()
1098 nullarbor:~ # echo -n 'func svc_process +p' >
1099 <debugfs>/dynamic_debug/control
1101 // disable all 12 messages in the function svc_process()
1102 nullarbor:~ # echo -n 'func svc_process -p' >
1103 <debugfs>/dynamic_debug/control
1105 See Documentation/dynamic-debug-howto.txt for additional information.
1107 config DMA_API_DEBUG
1108 bool "Enable debugging of DMA-API usage"
1109 depends on HAVE_DMA_API_DEBUG
1111 Enable this option to debug the use of the DMA API by device drivers.
1112 With this option you will be able to detect common bugs in device
1113 drivers like double-freeing of DMA mappings or freeing mappings that
1114 were never allocated.
1115 This option causes a performance degredation. Use only if you want
1116 to debug device drivers. If unsure, say N.
1118 config ATOMIC64_SELFTEST
1119 bool "Perform an atomic64_t self-test at boot"
1121 Enable this option to test the atomic64_t functions at boot.
1125 source "samples/Kconfig"
1127 source "lib/Kconfig.kgdb"
1129 source "lib/Kconfig.kmemcheck"