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_MUST_CHECK
13 bool "Enable __must_check logic"
16 Enable the __must_check logic in the kernel build. Disable this to
17 suppress the "warning: ignoring return value of 'foo', declared with
18 attribute warn_unused_result" messages.
21 bool "Magic SysRq key"
24 If you say Y here, you will have some control over the system even
25 if the system crashes for example during kernel debugging (e.g., you
26 will be able to flush the buffer cache to disk, reboot the system
27 immediately or dump some status information). This is accomplished
28 by pressing various keys while holding SysRq (Alt+PrintScreen). It
29 also works on a serial console (on PC hardware at least), if you
30 send a BREAK and then within 5 seconds a command keypress. The
31 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
32 unless you really know what this hack does.
35 bool "Enable unused/obsolete exported symbols"
38 Unused but exported symbols make the kernel needlessly bigger. For
39 that reason most of these unused exports will soon be removed. This
40 option is provided temporarily to provide a transition period in case
41 some external kernel module needs one of these symbols anyway. If you
42 encounter such a case in your module, consider if you are actually
43 using the right API. (rationale: since nobody in the kernel is using
44 this in a module, there is a pretty good chance it's actually the
45 wrong interface to use). If you really need the symbol, please send a
46 mail to the linux kernel mailing list mentioning the symbol and why
47 you really need it, and what the merge plan to the mainline kernel for
51 bool "Debug Filesystem"
54 debugfs is a virtual file system that kernel developers use to put
55 debugging files into. Enable this option to be able to read and
61 bool "Run 'make headers_check' when building vmlinux"
64 This option will extract the user-visible kernel headers whenever
65 building the kernel, and will run basic sanity checks on them to
66 ensure that exported files do not attempt to include files which
67 were not exported, etc.
69 If you're making modifications to header files which are
70 relevant for userspace, say 'Y', and check the headers
71 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
72 your build tree), to make sure they're suitable.
75 bool "Kernel debugging"
77 Say Y here if you are developing drivers or trying to debug and
78 identify kernel problems.
81 bool "Debug shared IRQ handlers"
82 depends on DEBUG_KERNEL && GENERIC_HARDIRQS
84 Enable this to generate a spurious interrupt as soon as a shared
85 interrupt handler is registered, and just before one is deregistered.
86 Drivers ought to be able to handle interrupts coming in at those
87 points; some don't and need to be caught.
90 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL
92 default 17 if S390 || LOCKDEP
93 default 16 if X86_NUMAQ || IA64
97 Select kernel log buffer size as a power of 2.
98 Defaults and Examples:
99 17 => 128 KB for S/390
100 16 => 64 KB for x86 NUMAQ or IA-64
102 14 => 16 KB for uniprocessor
106 config DETECT_SOFTLOCKUP
107 bool "Detect Soft Lockups"
108 depends on DEBUG_KERNEL && !S390
111 Say Y here to enable the kernel to detect "soft lockups",
112 which are bugs that cause the kernel to loop in kernel
113 mode for more than 10 seconds, without giving other tasks a
116 When a soft-lockup is detected, the kernel will print the
117 current stack trace (which you should report), but the
118 system will stay locked up. This feature has negligible
121 (Note that "hard lockups" are separate type of bugs that
122 can be detected via the NMI-watchdog, on platforms that
126 bool "Collect scheduler statistics"
127 depends on DEBUG_KERNEL && PROC_FS
129 If you say Y here, additional code will be inserted into the
130 scheduler and related routines to collect statistics about
131 scheduler behavior and provide them in /proc/schedstat. These
132 stats may be useful for both tuning and debugging the scheduler
133 If you aren't debugging the scheduler or trying to tune a specific
134 application, you can say N to avoid the very slight overhead
138 bool "Collect kernel timers statistics"
139 depends on DEBUG_KERNEL && PROC_FS
141 If you say Y here, additional code will be inserted into the
142 timer routines to collect statistics about kernel timers being
143 reprogrammed. The statistics can be read from /proc/timer_stats.
144 The statistics collection is started by writing 1 to /proc/timer_stats,
145 writing 0 stops it. This feature is useful to collect information
146 about timer usage patterns in kernel and userspace. This feature
147 is lightweight if enabled in the kernel config but not activated
148 (it defaults to deactivated on bootup and will only be activated
149 if some application like powertop activates it explicitly).
152 bool "Debug slab memory allocations"
153 depends on DEBUG_KERNEL && SLAB
155 Say Y here to have the kernel do limited verification on memory
156 allocation as well as poisoning memory on free to catch use of freed
157 memory. This can make kmalloc/kfree-intensive workloads much slower.
159 config DEBUG_SLAB_LEAK
160 bool "Memory leak debugging"
161 depends on DEBUG_SLAB
164 bool "Debug preemptible kernel"
165 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
168 If you say Y here then the kernel will use a debug variant of the
169 commonly used smp_processor_id() function and will print warnings
170 if kernel code uses it in a preemption-unsafe way. Also, the kernel
171 will detect preemption count underflows.
173 config DEBUG_RT_MUTEXES
174 bool "RT Mutex debugging, deadlock detection"
175 depends on DEBUG_KERNEL && RT_MUTEXES
177 This allows rt mutex semantics violations and rt mutex related
178 deadlocks (lockups) to be detected and reported automatically.
183 depends on DEBUG_RT_MUTEXES
185 config RT_MUTEX_TESTER
186 bool "Built-in scriptable tester for rt-mutexes"
187 depends on DEBUG_KERNEL && RT_MUTEXES
189 This option enables a rt-mutex tester.
191 config DEBUG_SPINLOCK
192 bool "Spinlock and rw-lock debugging: basic checks"
193 depends on DEBUG_KERNEL
195 Say Y here and build SMP to catch missing spinlock initialization
196 and certain other kinds of spinlock errors commonly made. This is
197 best used in conjunction with the NMI watchdog so that spinlock
198 deadlocks are also debuggable.
201 bool "Mutex debugging: basic checks"
202 depends on DEBUG_KERNEL
204 This feature allows mutex semantics violations to be detected and
207 config DEBUG_LOCK_ALLOC
208 bool "Lock debugging: detect incorrect freeing of live locks"
209 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
210 select DEBUG_SPINLOCK
214 This feature will check whether any held lock (spinlock, rwlock,
215 mutex or rwsem) is incorrectly freed by the kernel, via any of the
216 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),
217 vfree(), etc.), whether a live lock is incorrectly reinitialized via
218 spin_lock_init()/mutex_init()/etc., or whether there is any lock
219 held during task exit.
222 bool "Lock debugging: prove locking correctness"
223 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
225 select DEBUG_SPINLOCK
227 select DEBUG_LOCK_ALLOC
230 This feature enables the kernel to prove that all locking
231 that occurs in the kernel runtime is mathematically
232 correct: that under no circumstance could an arbitrary (and
233 not yet triggered) combination of observed locking
234 sequences (on an arbitrary number of CPUs, running an
235 arbitrary number of tasks and interrupt contexts) cause a
238 In short, this feature enables the kernel to report locking
239 related deadlocks before they actually occur.
241 The proof does not depend on how hard and complex a
242 deadlock scenario would be to trigger: how many
243 participant CPUs, tasks and irq-contexts would be needed
244 for it to trigger. The proof also does not depend on
245 timing: if a race and a resulting deadlock is possible
246 theoretically (no matter how unlikely the race scenario
247 is), it will be proven so and will immediately be
248 reported by the kernel (once the event is observed that
249 makes the deadlock theoretically possible).
251 If a deadlock is impossible (i.e. the locking rules, as
252 observed by the kernel, are mathematically correct), the
253 kernel reports nothing.
255 NOTE: this feature can also be enabled for rwlocks, mutexes
256 and rwsems - in which case all dependencies between these
257 different locking variants are observed and mapped too, and
258 the proof of observed correctness is also maintained for an
259 arbitrary combination of these separate locking variants.
261 For more details, see Documentation/lockdep-design.txt.
265 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
267 select FRAME_POINTER if !X86
272 bool "Lock dependency engine debugging"
273 depends on DEBUG_KERNEL && LOCKDEP
275 If you say Y here, the lock dependency engine will do
276 additional runtime checks to debug itself, at the price
277 of more runtime overhead.
279 config TRACE_IRQFLAGS
280 depends on DEBUG_KERNEL
283 depends on TRACE_IRQFLAGS_SUPPORT
284 depends on PROVE_LOCKING
286 config DEBUG_SPINLOCK_SLEEP
287 bool "Spinlock debugging: sleep-inside-spinlock checking"
288 depends on DEBUG_KERNEL
290 If you say Y here, various routines which may sleep will become very
291 noisy if they are called with a spinlock held.
293 config DEBUG_LOCKING_API_SELFTESTS
294 bool "Locking API boot-time self-tests"
295 depends on DEBUG_KERNEL
297 Say Y here if you want the kernel to run a short self-test during
298 bootup. The self-test checks whether common types of locking bugs
299 are detected by debugging mechanisms or not. (if you disable
300 lock debugging then those bugs wont be detected of course.)
301 The following locking APIs are covered: spinlocks, rwlocks,
306 depends on DEBUG_KERNEL
307 depends on STACKTRACE_SUPPORT
310 bool "kobject debugging"
311 depends on DEBUG_KERNEL
313 If you say Y here, some extra kobject debugging messages will be sent
317 bool "Highmem debugging"
318 depends on DEBUG_KERNEL && HIGHMEM
320 This options enables addition error checking for high memory systems.
321 Disable for production systems.
323 config DEBUG_BUGVERBOSE
324 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
326 depends on ARM || ARM26 || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG
329 Say Y here to make BUG() panics output the file name and line number
330 of the BUG call as well as the EIP and oops trace. This aids
331 debugging but costs about 70-100K of memory.
334 bool "Compile the kernel with debug info"
335 depends on DEBUG_KERNEL
337 If you say Y here the resulting kernel image will include
338 debugging info resulting in a larger kernel image.
339 Say Y here only if you plan to debug the kernel.
345 depends on DEBUG_KERNEL
347 Enable this to turn on extended checks in the virtual-memory system
348 that may impact performance.
353 bool "Debug linked list manipulation"
354 depends on DEBUG_KERNEL
356 Enable this to turn on extended checks in the linked-list
362 bool "Compile the kernel with frame pointers"
363 depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH)
364 default y if DEBUG_INFO && UML
366 If you say Y here the resulting kernel image will be slightly larger
367 and slower, but it might give very useful debugging information on
368 some architectures or if you use external debuggers.
369 If you don't debug the kernel, you can say N.
371 config FORCED_INLINING
372 bool "Force gcc to inline functions marked 'inline'"
373 depends on DEBUG_KERNEL
376 This option determines if the kernel forces gcc to inline the functions
377 developers have marked 'inline'. Doing so takes away freedom from gcc to
378 do what it thinks is best, which is desirable for the gcc 3.x series of
379 compilers. The gcc 4.x series have a rewritten inlining algorithm and
380 disabling this option will generate a smaller kernel there. Hopefully
381 this algorithm is so good that allowing gcc4 to make the decision can
382 become the default in the future, until then this option is there to
385 config RCU_TORTURE_TEST
386 tristate "torture tests for RCU"
387 depends on DEBUG_KERNEL
390 This option provides a kernel module that runs torture tests
391 on the RCU infrastructure. The kernel module may be built
392 after the fact on the running kernel to be tested, if desired.
394 Say Y here if you want RCU torture tests to start automatically
395 at boot time (you probably don't).
396 Say M if you want the RCU torture tests to build as a module.
397 Say N if you are unsure.
400 tristate "Linux Kernel Dump Test Tool Module"
401 depends on DEBUG_KERNEL
405 This module enables testing of the different dumping mechanisms by
406 inducing system failures at predefined crash points.
407 If you don't need it: say N
408 Choose M here to compile this code as a module. The module will be
411 Documentation on how to use the module can be found in
414 config FAULT_INJECTION
415 bool "Fault-injection framework"
416 depends on DEBUG_KERNEL
418 Provide fault-injection framework.
419 For more details, see Documentation/fault-injection/.
422 bool "Fault-injection capability for kmalloc"
423 depends on FAULT_INJECTION
425 Provide fault-injection capability for kmalloc.
427 config FAIL_PAGE_ALLOC
428 bool "Fault-injection capabilitiy for alloc_pages()"
429 depends on FAULT_INJECTION
431 Provide fault-injection capability for alloc_pages().
433 config FAIL_MAKE_REQUEST
434 bool "Fault-injection capability for disk IO"
435 depends on FAULT_INJECTION
437 Provide fault-injection capability for disk IO.
439 config FAULT_INJECTION_DEBUG_FS
440 bool "Debugfs entries for fault-injection capabilities"
441 depends on FAULT_INJECTION && SYSFS && DEBUG_FS
443 Enable configuration of fault-injection capabilities via debugfs.
445 config FAULT_INJECTION_STACKTRACE_FILTER
446 bool "stacktrace filter for fault-injection capabilities"
447 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
451 Provide stacktrace filter for fault-injection capabilities