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 bool "Magic SysRq key"
32 If you say Y here, you will have some control over the system even
33 if the system crashes for example during kernel debugging (e.g., you
34 will be able to flush the buffer cache to disk, reboot the system
35 immediately or dump some status information). This is accomplished
36 by pressing various keys while holding SysRq (Alt+PrintScreen). It
37 also works on a serial console (on PC hardware at least), if you
38 send a BREAK and then within 5 seconds a command keypress. The
39 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
40 unless you really know what this hack does.
43 bool "Enable unused/obsolete exported symbols"
46 Unused but exported symbols make the kernel needlessly bigger. For
47 that reason most of these unused exports will soon be removed. This
48 option is provided temporarily to provide a transition period in case
49 some external kernel module needs one of these symbols anyway. If you
50 encounter such a case in your module, consider if you are actually
51 using the right API. (rationale: since nobody in the kernel is using
52 this in a module, there is a pretty good chance it's actually the
53 wrong interface to use). If you really need the symbol, please send a
54 mail to the linux kernel mailing list mentioning the symbol and why
55 you really need it, and what the merge plan to the mainline kernel for
59 bool "Debug Filesystem"
62 debugfs is a virtual file system that kernel developers use to put
63 debugging files into. Enable this option to be able to read and
69 bool "Run 'make headers_check' when building vmlinux"
72 This option will extract the user-visible kernel headers whenever
73 building the kernel, and will run basic sanity checks on them to
74 ensure that exported files do not attempt to include files which
75 were not exported, etc.
77 If you're making modifications to header files which are
78 relevant for userspace, say 'Y', and check the headers
79 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
80 your build tree), to make sure they're suitable.
82 config DEBUG_SECTION_MISMATCH
83 bool "Enable full Section mismatch analysis"
86 The section mismatch analysis checks if there are illegal
87 references from one section to another section.
88 Linux will during link or during runtime drop some sections
89 and any use of code/data previously in these sections will
90 most likely result in an oops.
91 In the code functions and variables are annotated with
92 __init, __devinit etc. (see full list in include/linux/init.h)
93 which result in the code/data being placed in specific sections.
94 The section mismatch anaylsis are always done after a full
95 kernel build but enabling this options will in addition
97 - Add the option -fno-inline-functions-called-once to gcc
98 When inlining a function annotated __init in a non-init
99 function we would loose the section information and thus
100 the analysis would not catch the illegal reference.
101 This options tell gcc to inline less but will also
102 result in a larger kernel.
103 - Run the section mismatch analysis for each module/built-in.o
104 When we run the section mismatch analysis on vmlinux.o we
105 looses valueable information about where the mismatch was
107 Running the analysis for each module/built-in.o file
108 will tell where the mismatch happens much closer to the
109 source. The drawback is that we will report the same
110 mismatch at least twice.
113 bool "Kernel debugging"
115 Say Y here if you are developing drivers or trying to debug and
116 identify kernel problems.
119 bool "Debug shared IRQ handlers"
120 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
122 Enable this to generate a spurious interrupt as soon as a shared
123 interrupt handler is registered, and just before one is deregistered.
124 Drivers ought to be able to handle interrupts coming in at those
125 points; some don't and need to be caught.
127 config DETECT_SOFTLOCKUP
128 bool "Detect Soft Lockups"
129 depends on DEBUG_KERNEL && !S390
132 Say Y here to enable the kernel to detect "soft lockups",
133 which are bugs that cause the kernel to loop in kernel
134 mode for more than 10 seconds, without giving other tasks a
137 When a soft-lockup is detected, the kernel will print the
138 current stack trace (which you should report), but the
139 system will stay locked up. This feature has negligible
142 (Note that "hard lockups" are separate type of bugs that
143 can be detected via the NMI-watchdog, on platforms that
147 bool "Collect scheduler debugging info"
148 depends on DEBUG_KERNEL && PROC_FS
151 If you say Y here, the /proc/sched_debug file will be provided
152 that can help debug the scheduler. The runtime overhead of this
156 bool "Collect scheduler statistics"
157 depends on DEBUG_KERNEL && PROC_FS
159 If you say Y here, additional code will be inserted into the
160 scheduler and related routines to collect statistics about
161 scheduler behavior and provide them in /proc/schedstat. These
162 stats may be useful for both tuning and debugging the scheduler
163 If you aren't debugging the scheduler or trying to tune a specific
164 application, you can say N to avoid the very slight overhead
168 bool "Collect kernel timers statistics"
169 depends on DEBUG_KERNEL && PROC_FS
171 If you say Y here, additional code will be inserted into the
172 timer routines to collect statistics about kernel timers being
173 reprogrammed. The statistics can be read from /proc/timer_stats.
174 The statistics collection is started by writing 1 to /proc/timer_stats,
175 writing 0 stops it. This feature is useful to collect information
176 about timer usage patterns in kernel and userspace. This feature
177 is lightweight if enabled in the kernel config but not activated
178 (it defaults to deactivated on bootup and will only be activated
179 if some application like powertop activates it explicitly).
182 bool "Debug slab memory allocations"
183 depends on DEBUG_KERNEL && SLAB
185 Say Y here to have the kernel do limited verification on memory
186 allocation as well as poisoning memory on free to catch use of freed
187 memory. This can make kmalloc/kfree-intensive workloads much slower.
189 config DEBUG_SLAB_LEAK
190 bool "Memory leak debugging"
191 depends on DEBUG_SLAB
194 bool "SLUB debugging on by default"
195 depends on SLUB && SLUB_DEBUG
198 Boot with debugging on by default. SLUB boots by default with
199 the runtime debug capabilities switched off. Enabling this is
200 equivalent to specifying the "slub_debug" parameter on boot.
201 There is no support for more fine grained debug control like
202 possible with slub_debug=xxx. SLUB debugging may be switched
203 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
207 bool "Debug preemptible kernel"
208 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64)
211 If you say Y here then the kernel will use a debug variant of the
212 commonly used smp_processor_id() function and will print warnings
213 if kernel code uses it in a preemption-unsafe way. Also, the kernel
214 will detect preemption count underflows.
216 config DEBUG_RT_MUTEXES
217 bool "RT Mutex debugging, deadlock detection"
218 depends on DEBUG_KERNEL && RT_MUTEXES
220 This allows rt mutex semantics violations and rt mutex related
221 deadlocks (lockups) to be detected and reported automatically.
226 depends on DEBUG_RT_MUTEXES
228 config RT_MUTEX_TESTER
229 bool "Built-in scriptable tester for rt-mutexes"
230 depends on DEBUG_KERNEL && RT_MUTEXES
232 This option enables a rt-mutex tester.
234 config DEBUG_SPINLOCK
235 bool "Spinlock and rw-lock debugging: basic checks"
236 depends on DEBUG_KERNEL
238 Say Y here and build SMP to catch missing spinlock initialization
239 and certain other kinds of spinlock errors commonly made. This is
240 best used in conjunction with the NMI watchdog so that spinlock
241 deadlocks are also debuggable.
244 bool "Mutex debugging: basic checks"
245 depends on DEBUG_KERNEL
247 This feature allows mutex semantics violations to be detected and
250 config DEBUG_SEMAPHORE
251 bool "Semaphore debugging"
252 depends on DEBUG_KERNEL
253 depends on ALPHA || FRV
256 If you say Y here then semaphore processing will issue lots of
257 verbose debugging messages. If you suspect a semaphore problem or a
258 kernel hacker asks for this option then say Y. Otherwise say N.
260 config DEBUG_LOCK_ALLOC
261 bool "Lock debugging: detect incorrect freeing of live locks"
262 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
263 select DEBUG_SPINLOCK
267 This feature will check whether any held lock (spinlock, rwlock,
268 mutex or rwsem) is incorrectly freed by the kernel, via any of the
269 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
270 vfree(), etc.), whether a live lock is incorrectly reinitialized via
271 spin_lock_init()/mutex_init()/etc., or whether there is any lock
272 held during task exit.
275 bool "Lock debugging: prove locking correctness"
276 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
278 select DEBUG_SPINLOCK
280 select DEBUG_LOCK_ALLOC
283 This feature enables the kernel to prove that all locking
284 that occurs in the kernel runtime is mathematically
285 correct: that under no circumstance could an arbitrary (and
286 not yet triggered) combination of observed locking
287 sequences (on an arbitrary number of CPUs, running an
288 arbitrary number of tasks and interrupt contexts) cause a
291 In short, this feature enables the kernel to report locking
292 related deadlocks before they actually occur.
294 The proof does not depend on how hard and complex a
295 deadlock scenario would be to trigger: how many
296 participant CPUs, tasks and irq-contexts would be needed
297 for it to trigger. The proof also does not depend on
298 timing: if a race and a resulting deadlock is possible
299 theoretically (no matter how unlikely the race scenario
300 is), it will be proven so and will immediately be
301 reported by the kernel (once the event is observed that
302 makes the deadlock theoretically possible).
304 If a deadlock is impossible (i.e. the locking rules, as
305 observed by the kernel, are mathematically correct), the
306 kernel reports nothing.
308 NOTE: this feature can also be enabled for rwlocks, mutexes
309 and rwsems - in which case all dependencies between these
310 different locking variants are observed and mapped too, and
311 the proof of observed correctness is also maintained for an
312 arbitrary combination of these separate locking variants.
314 For more details, see Documentation/lockdep-design.txt.
318 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
320 select FRAME_POINTER if !X86 && !MIPS
325 bool "Lock usage statistics"
326 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
328 select DEBUG_SPINLOCK
330 select DEBUG_LOCK_ALLOC
333 This feature enables tracking lock contention points
335 For more details, see Documentation/lockstat.txt
338 bool "Lock dependency engine debugging"
339 depends on DEBUG_KERNEL && LOCKDEP
341 If you say Y here, the lock dependency engine will do
342 additional runtime checks to debug itself, at the price
343 of more runtime overhead.
345 config TRACE_IRQFLAGS
346 depends on DEBUG_KERNEL
349 depends on TRACE_IRQFLAGS_SUPPORT
350 depends on PROVE_LOCKING
352 config DEBUG_SPINLOCK_SLEEP
353 bool "Spinlock debugging: sleep-inside-spinlock checking"
354 depends on DEBUG_KERNEL
356 If you say Y here, various routines which may sleep will become very
357 noisy if they are called with a spinlock held.
359 config DEBUG_LOCKING_API_SELFTESTS
360 bool "Locking API boot-time self-tests"
361 depends on DEBUG_KERNEL
363 Say Y here if you want the kernel to run a short self-test during
364 bootup. The self-test checks whether common types of locking bugs
365 are detected by debugging mechanisms or not. (if you disable
366 lock debugging then those bugs wont be detected of course.)
367 The following locking APIs are covered: spinlocks, rwlocks,
372 depends on DEBUG_KERNEL
373 depends on STACKTRACE_SUPPORT
376 bool "kobject debugging"
377 depends on DEBUG_KERNEL
379 If you say Y here, some extra kobject debugging messages will be sent
383 bool "Highmem debugging"
384 depends on DEBUG_KERNEL && HIGHMEM
386 This options enables addition error checking for high memory systems.
387 Disable for production systems.
389 config DEBUG_BUGVERBOSE
390 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
392 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG || BLACKFIN
395 Say Y here to make BUG() panics output the file name and line number
396 of the BUG call as well as the EIP and oops trace. This aids
397 debugging but costs about 70-100K of memory.
400 bool "Compile the kernel with debug info"
401 depends on DEBUG_KERNEL
403 If you say Y here the resulting kernel image will include
404 debugging info resulting in a larger kernel image.
405 This adds debug symbols to the kernel and modules (gcc -g), and
406 is needed if you intend to use kernel crashdump or binary object
407 tools like crash, kgdb, LKCD, gdb, etc on the kernel.
408 Say Y here only if you plan to debug the kernel.
414 depends on DEBUG_KERNEL
416 Enable this to turn on extended checks in the virtual-memory system
417 that may impact performance.
422 bool "Debug linked list manipulation"
423 depends on DEBUG_KERNEL
425 Enable this to turn on extended checks in the linked-list
431 bool "Debug SG table operations"
432 depends on DEBUG_KERNEL
434 Enable this to turn on checks on scatter-gather tables. This can
435 help find problems with drivers that do not properly initialize
441 bool "Compile the kernel with frame pointers"
442 depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH || BLACKFIN)
443 default y if DEBUG_INFO && UML
445 If you say Y here the resulting kernel image will be slightly larger
446 and slower, but it might give very useful debugging information on
447 some architectures or if you use external debuggers.
448 If you don't debug the kernel, you can say N.
450 config FORCED_INLINING
451 bool "Force gcc to inline functions marked 'inline'"
452 depends on DEBUG_KERNEL
455 This option determines if the kernel forces gcc to inline the functions
456 developers have marked 'inline'. Doing so takes away freedom from gcc to
457 do what it thinks is best, which is desirable for the gcc 3.x series of
458 compilers. The gcc 4.x series have a rewritten inlining algorithm and
459 disabling this option will generate a smaller kernel there. Hopefully
460 this algorithm is so good that allowing gcc4 to make the decision can
461 become the default in the future, until then this option is there to
464 config BOOT_PRINTK_DELAY
465 bool "Delay each boot printk message by N milliseconds"
466 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY
468 This build option allows you to read kernel boot messages
469 by inserting a short delay after each one. The delay is
470 specified in milliseconds on the kernel command line,
471 using "boot_delay=N".
473 It is likely that you would also need to use "lpj=M" to preset
474 the "loops per jiffie" value.
475 See a previous boot log for the "lpj" value to use for your
476 system, and then set "lpj=M" before setting "boot_delay=N".
477 NOTE: Using this option may adversely affect SMP systems.
478 I.e., processors other than the first one may not boot up.
479 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect
480 what it believes to be lockup conditions.
482 config RCU_TORTURE_TEST
483 tristate "torture tests for RCU"
484 depends on DEBUG_KERNEL
488 This option provides a kernel module that runs torture tests
489 on the RCU infrastructure. The kernel module may be built
490 after the fact on the running kernel to be tested, if desired.
492 Say M if you want the RCU torture tests to build as a module.
493 Say N if you are unsure.
496 tristate "Linux Kernel Dump Test Tool Module"
497 depends on DEBUG_KERNEL
501 This module enables testing of the different dumping mechanisms by
502 inducing system failures at predefined crash points.
503 If you don't need it: say N
504 Choose M here to compile this code as a module. The module will be
507 Documentation on how to use the module can be found in
510 config FAULT_INJECTION
511 bool "Fault-injection framework"
512 depends on DEBUG_KERNEL
514 Provide fault-injection framework.
515 For more details, see Documentation/fault-injection/.
518 bool "Fault-injection capability for kmalloc"
519 depends on FAULT_INJECTION
521 Provide fault-injection capability for kmalloc.
523 config FAIL_PAGE_ALLOC
524 bool "Fault-injection capabilitiy for alloc_pages()"
525 depends on FAULT_INJECTION
527 Provide fault-injection capability for alloc_pages().
529 config FAIL_MAKE_REQUEST
530 bool "Fault-injection capability for disk IO"
531 depends on FAULT_INJECTION
533 Provide fault-injection capability for disk IO.
535 config FAULT_INJECTION_DEBUG_FS
536 bool "Debugfs entries for fault-injection capabilities"
537 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
539 Enable configuration of fault-injection capabilities via debugfs.
541 config FAULT_INJECTION_STACKTRACE_FILTER
542 bool "stacktrace filter for fault-injection capabilities"
543 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
548 Provide stacktrace filter for fault-injection capabilities
551 bool "Latency measuring infrastructure"
552 select FRAME_POINTER if !MIPS
558 depends on X86 || X86_64
560 Enable this option if you want to use the LatencyTOP tool
561 to find out which userspace is blocking on what kernel operations.
564 source "samples/Kconfig"