config PRINTK_TIME

bool "Show timing information on printks"

depends on PRINTK

help

Selecting this option causes timing information to be

included in printk output. This allows you to measure

the interval between kernel operations, including bootup

operations. This is useful for identifying long delays

in kernel startup.

config ENABLE_MUST_CHECK

bool "Enable __must_check logic"

default y

help

Enable the __must_check logic in the kernel build. Disable this to

suppress the "warning: ignoring return value of 'foo', declared with

attribute warn_unused_result" messages.

config MAGIC_SYSRQ

bool "Magic SysRq key"

depends on !UML

help

If you say Y here, you will have some control over the system even

if the system crashes for example during kernel debugging (e.g., you

will be able to flush the buffer cache to disk, reboot the system

immediately or dump some status information). This is accomplished

by pressing various keys while holding SysRq (Alt+PrintScreen). It

also works on a serial console (on PC hardware at least), if you

send a BREAK and then within 5 seconds a command keypress. The

keys are documented in <file:Documentation/sysrq.txt>. Don't say Y

unless you really know what this hack does.

config UNUSED_SYMBOLS

bool "Enable unused/obsolete exported symbols"

default y if X86

help

Unused but exported symbols make the kernel needlessly bigger. For

that reason most of these unused exports will soon be removed. This

option is provided temporarily to provide a transition period in case

some external kernel module needs one of these symbols anyway. If you

encounter such a case in your module, consider if you are actually

using the right API. (rationale: since nobody in the kernel is using

this in a module, there is a pretty good chance it's actually the

wrong interface to use). If you really need the symbol, please send a

mail to the linux kernel mailing list mentioning the symbol and why

you really need it, and what the merge plan to the mainline kernel for

your module is.

config DEBUG_FS

bool "Debug Filesystem"

depends on SYSFS

help

debugfs is a virtual file system that kernel developers use to put

debugging files into. Enable this option to be able to read and

write to these files.

If unsure, say N.

config HEADERS_CHECK

bool "Run 'make headers_check' when building vmlinux"

depends on !UML

help

This option will extract the user-visible kernel headers whenever

building the kernel, and will run basic sanity checks on them to

ensure that exported files do not attempt to include files which

were not exported, etc.

If you're making modifications to header files which are

relevant for userspace, say 'Y', and check the headers

exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in

your build tree), to make sure they're suitable.

config DEBUG_KERNEL

bool "Kernel debugging"

help

Say Y here if you are developing drivers or trying to debug and

identify kernel problems.

config DEBUG_SHIRQ

bool "Debug shared IRQ handlers"

depends on DEBUG_KERNEL && GENERIC_HARDIRQS

help

Enable this to generate a spurious interrupt as soon as a shared

interrupt handler is registered, and just before one is deregistered.

Drivers ought to be able to handle interrupts coming in at those

points; some don't and need to be caught.

config DETECT_SOFTLOCKUP

bool "Detect Soft Lockups"

depends on DEBUG_KERNEL && !S390

default y

help

Say Y here to enable the kernel to detect "soft lockups",

which are bugs that cause the kernel to loop in kernel

mode for more than 10 seconds, without giving other tasks a

chance to run.

When a soft-lockup is detected, the kernel will print the

current stack trace (which you should report), but the

system will stay locked up. This feature has negligible

overhead.

(Note that "hard lockups" are separate type of bugs that

can be detected via the NMI-watchdog, on platforms that

support it.)

config SCHED_DEBUG

bool "Collect scheduler debugging info"

depends on DEBUG_KERNEL && PROC_FS

default y

help

If you say Y here, the /proc/sched_debug file will be provided

that can help debug the scheduler. The runtime overhead of this

option is minimal.

config SCHEDSTATS

bool "Collect scheduler statistics"

depends on DEBUG_KERNEL && PROC_FS

help

If you say Y here, additional code will be inserted into the

scheduler and related routines to collect statistics about

scheduler behavior and provide them in /proc/schedstat. These

stats may be useful for both tuning and debugging the scheduler

If you aren't debugging the scheduler or trying to tune a specific

application, you can say N to avoid the very slight overhead

this adds.

config TIMER_STATS

bool "Collect kernel timers statistics"

depends on DEBUG_KERNEL && PROC_FS

help

If you say Y here, additional code will be inserted into the

timer routines to collect statistics about kernel timers being

reprogrammed. The statistics can be read from /proc/timer_stats.

The statistics collection is started by writing 1 to /proc/timer_stats,

writing 0 stops it. This feature is useful to collect information

about timer usage patterns in kernel and userspace. This feature

is lightweight if enabled in the kernel config but not activated

(it defaults to deactivated on bootup and will only be activated

if some application like powertop activates it explicitly).

config DEBUG_SLAB

bool "Debug slab memory allocations"

depends on DEBUG_KERNEL && SLAB

help

Say Y here to have the kernel do limited verification on memory

allocation as well as poisoning memory on free to catch use of freed

memory. This can make kmalloc/kfree-intensive workloads much slower.

config DEBUG_SLAB_LEAK

bool "Memory leak debugging"

depends on DEBUG_SLAB

config SLUB_DEBUG_ON

bool "SLUB debugging on by default"

depends on SLUB && SLUB_DEBUG

default n

help

Boot with debugging on by default. SLUB boots by default with

the runtime debug capabilities switched off. Enabling this is

equivalent to specifying the "slub_debug" parameter on boot.

There is no support for more fine grained debug control like

possible with slub_debug=xxx. SLUB debugging may be switched

off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying

"slub_debug=-".

config DEBUG_PREEMPT

bool "Debug preemptible kernel"

depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64)

default y

help

If you say Y here then the kernel will use a debug variant of the

commonly used smp_processor_id() function and will print warnings

if kernel code uses it in a preemption-unsafe way. Also, the kernel

will detect preemption count underflows.

config DEBUG_RT_MUTEXES

bool "RT Mutex debugging, deadlock detection"

depends on DEBUG_KERNEL && RT_MUTEXES

help

This allows rt mutex semantics violations and rt mutex related

deadlocks (lockups) to be detected and reported automatically.

config DEBUG_PI_LIST

bool

default y

depends on DEBUG_RT_MUTEXES

config RT_MUTEX_TESTER

bool "Built-in scriptable tester for rt-mutexes"

depends on DEBUG_KERNEL && RT_MUTEXES

help

This option enables a rt-mutex tester.

config DEBUG_SPINLOCK

bool "Spinlock and rw-lock debugging: basic checks"

depends on DEBUG_KERNEL

help

Say Y here and build SMP to catch missing spinlock initialization

and certain other kinds of spinlock errors commonly made. This is

best used in conjunction with the NMI watchdog so that spinlock

deadlocks are also debuggable.

config DEBUG_MUTEXES

bool "Mutex debugging: basic checks"

depends on DEBUG_KERNEL

help

This feature allows mutex semantics violations to be detected and

reported.

config DEBUG_SEMAPHORE

bool "Semaphore debugging"

depends on DEBUG_KERNEL

depends on ALPHA || FRV

default n

help

If you say Y here then semaphore processing will issue lots of

verbose debugging messages. If you suspect a semaphore problem or a

kernel hacker asks for this option then say Y. Otherwise say N.

config DEBUG_LOCK_ALLOC

bool "Lock debugging: detect incorrect freeing of live locks"

depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

select DEBUG_SPINLOCK

select DEBUG_MUTEXES

select LOCKDEP

help

This feature will check whether any held lock (spinlock, rwlock,

mutex or rwsem) is incorrectly freed by the kernel, via any of the

memory-freeing routines (kfree(), kmem_cache_free(), free_pages(),

vfree(), etc.), whether a live lock is incorrectly reinitialized via

spin_lock_init()/mutex_init()/etc., or whether there is any lock

held during task exit.

config PROVE_LOCKING

bool "Lock debugging: prove locking correctness"

depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

select LOCKDEP

select DEBUG_SPINLOCK

select DEBUG_MUTEXES

select DEBUG_LOCK_ALLOC

default n

help

This feature enables the kernel to prove that all locking

that occurs in the kernel runtime is mathematically

correct: that under no circumstance could an arbitrary (and

not yet triggered) combination of observed locking

sequences (on an arbitrary number of CPUs, running an

arbitrary number of tasks and interrupt contexts) cause a

deadlock.

In short, this feature enables the kernel to report locking

related deadlocks before they actually occur.

The proof does not depend on how hard and complex a

deadlock scenario would be to trigger: how many

participant CPUs, tasks and irq-contexts would be needed

for it to trigger. The proof also does not depend on

timing: if a race and a resulting deadlock is possible

theoretically (no matter how unlikely the race scenario

is), it will be proven so and will immediately be

reported by the kernel (once the event is observed that

makes the deadlock theoretically possible).

If a deadlock is impossible (i.e. the locking rules, as

observed by the kernel, are mathematically correct), the

kernel reports nothing.

NOTE: this feature can also be enabled for rwlocks, mutexes

and rwsems - in which case all dependencies between these

different locking variants are observed and mapped too, and

the proof of observed correctness is also maintained for an

arbitrary combination of these separate locking variants.

For more details, see Documentation/lockdep-design.txt.

config LOCKDEP

bool

depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

select STACKTRACE

select FRAME_POINTER if !X86 && !MIPS

select KALLSYMS

select KALLSYMS_ALL

config LOCK_STAT

bool "Lock usage statistics"

depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

select LOCKDEP

select DEBUG_SPINLOCK

select DEBUG_MUTEXES

select DEBUG_LOCK_ALLOC

default n

help

This feature enables tracking lock contention points

For more details, see Documentation/lockstat.txt

config DEBUG_LOCKDEP

bool "Lock dependency engine debugging"

depends on DEBUG_KERNEL && LOCKDEP

help

If you say Y here, the lock dependency engine will do

additional runtime checks to debug itself, at the price

of more runtime overhead.

config TRACE_IRQFLAGS

depends on DEBUG_KERNEL

bool

default y

depends on TRACE_IRQFLAGS_SUPPORT

depends on PROVE_LOCKING

config DEBUG_SPINLOCK_SLEEP

bool "Spinlock debugging: sleep-inside-spinlock checking"

depends on DEBUG_KERNEL

help

If you say Y here, various routines which may sleep will become very

noisy if they are called with a spinlock held.

config DEBUG_LOCKING_API_SELFTESTS

bool "Locking API boot-time self-tests"

depends on DEBUG_KERNEL

help

Say Y here if you want the kernel to run a short self-test during

bootup. The self-test checks whether common types of locking bugs

are detected by debugging mechanisms or not. (if you disable

lock debugging then those bugs wont be detected of course.)

The following locking APIs are covered: spinlocks, rwlocks,

mutexes and rwsems.

config STACKTRACE

bool

depends on DEBUG_KERNEL

depends on STACKTRACE_SUPPORT

config DEBUG_KOBJECT

bool "kobject debugging"

depends on DEBUG_KERNEL

help

If you say Y here, some extra kobject debugging messages will be sent

to the syslog.

config DEBUG_HIGHMEM

bool "Highmem debugging"

depends on DEBUG_KERNEL && HIGHMEM

help

This options enables addition error checking for high memory systems.

Disable for production systems.

config DEBUG_BUGVERBOSE

bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED

depends on BUG

depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG || BFIN

default !EMBEDDED

help

Say Y here to make BUG() panics output the file name and line number

of the BUG call as well as the EIP and oops trace. This aids

debugging but costs about 70-100K of memory.

config DEBUG_INFO

bool "Compile the kernel with debug info"

depends on DEBUG_KERNEL

help

If you say Y here the resulting kernel image will include

debugging info resulting in a larger kernel image.

This adds debug symbols to the kernel and modules (gcc -g), and

is needed if you intend to use kernel crashdump or binary object

tools like crash, kgdb, LKCD, gdb, etc on the kernel.

Say Y here only if you plan to debug the kernel.

If unsure, say N.

config DEBUG_VM

bool "Debug VM"

depends on DEBUG_KERNEL

help

Enable this to turn on extended checks in the virtual-memory system

that may impact performance.

If unsure, say N.

config DEBUG_LIST

bool "Debug linked list manipulation"

depends on DEBUG_KERNEL

help

Enable this to turn on extended checks in the linked-list

walking routines.

If unsure, say N.

config FRAME_POINTER

bool "Compile the kernel with frame pointers"

depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH || BFIN)

default y if DEBUG_INFO && UML

help

If you say Y here the resulting kernel image will be slightly larger

and slower, but it might give very useful debugging information on

some architectures or if you use external debuggers.

If you don't debug the kernel, you can say N.

config FORCED_INLINING

bool "Force gcc to inline functions marked 'inline'"

depends on DEBUG_KERNEL

default y

help

This option determines if the kernel forces gcc to inline the functions

developers have marked 'inline'. Doing so takes away freedom from gcc to

do what it thinks is best, which is desirable for the gcc 3.x series of

compilers. The gcc 4.x series have a rewritten inlining algorithm and

disabling this option will generate a smaller kernel there. Hopefully

this algorithm is so good that allowing gcc4 to make the decision can

become the default in the future, until then this option is there to

test gcc for this.

config BOOT_PRINTK_DELAY

bool "Delay each boot printk message by N milliseconds"

depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY

help

This build option allows you to read kernel boot messages

by inserting a short delay after each one. The delay is

specified in milliseconds on the kernel command line,

using "boot_delay=N".

It is likely that you would also need to use "lpj=M" to preset

the "loops per jiffie" value.

See a previous boot log for the "lpj" value to use for your

system, and then set "lpj=M" before setting "boot_delay=N".

NOTE: Using this option may adversely affect SMP systems.

I.e., processors other than the first one may not boot up.

BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect

what it believes to be lockup conditions.

config RCU_TORTURE_TEST

tristate "torture tests for RCU"

depends on DEBUG_KERNEL

depends on m

default n

help

This option provides a kernel module that runs torture tests

on the RCU infrastructure. The kernel module may be built

after the fact on the running kernel to be tested, if desired.

Say M if you want the RCU torture tests to build as a module.

Say N if you are unsure.

config LKDTM

tristate "Linux Kernel Dump Test Tool Module"

depends on DEBUG_KERNEL

depends on KPROBES

default n

help

This module enables testing of the different dumping mechanisms by

inducing system failures at predefined crash points.

If you don't need it: say N

Choose M here to compile this code as a module. The module will be

called lkdtm.

Documentation on how to use the module can be found in

drivers/misc/lkdtm.c

config FAULT_INJECTION

bool "Fault-injection framework"

depends on DEBUG_KERNEL

help

Provide fault-injection framework.

For more details, see Documentation/fault-injection/.

config FAILSLAB

bool "Fault-injection capability for kmalloc"

depends on FAULT_INJECTION

help

Provide fault-injection capability for kmalloc.

config FAIL_PAGE_ALLOC

bool "Fault-injection capabilitiy for alloc_pages()"

depends on FAULT_INJECTION

help

Provide fault-injection capability for alloc_pages().

config FAIL_MAKE_REQUEST

bool "Fault-injection capability for disk IO"

depends on FAULT_INJECTION

help

Provide fault-injection capability for disk IO.

config FAULT_INJECTION_DEBUG_FS

bool "Debugfs entries for fault-injection capabilities"

depends on FAULT_INJECTION && SYSFS && DEBUG_FS

help

Enable configuration of fault-injection capabilities via debugfs.

config FAULT_INJECTION_STACKTRACE_FILTER

bool "stacktrace filter for fault-injection capabilities"

depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT

depends on !X86_64

select STACKTRACE

select FRAME_POINTER

help

Provide stacktrace filter for fault-injection capabilities