lib/Kconfig.debug - linux - Git at Google



            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_WARN_DEPRECATED

            
            	bool "Enable __deprecated logic"

            
            	default y

            
            	help

            
            	  Enable the __deprecated logic in the kernel build.

            
            	  Disable this to suppress the "warning: 'foo' is deprecated

            
            	  (declared at kernel/power/somefile.c:1234)" messages.


            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_SECTION_MISMATCH

            
            	bool "Enable full Section mismatch analysis"

            
            	default n

            
            	help

            
            	  The section mismatch analysis checks if there are illegal

            
            	  references from one section to another section.

            
            	  Linux will during link or during runtime drop some sections

            
            	  and any use of code/data previously in these sections will

            
            	  most likely result in an oops.

            
            	  In the code functions and variables are annotated with

            
            	  __init, __devinit etc. (see full list in include/linux/init.h)

            
            	  which result in the code/data being placed in specific sections.

            
            	  The section mismatch anaylsis are always done after a full

            
            	  kernel build but enabling this options will in addition

            
            	  do the following:

            
            	  - Add the option -fno-inline-functions-called-once to gcc

            
            	    When inlining a function annotated __init in a non-init

            
            	    function we would loose the section information and thus

            
            	    the analysis would not catch the illegal reference.

            
            	    This options tell gcc to inline less but will also

            
            	    result in a larger kernel.

            
            	  - Run the section mismatch analysis for each module/built-in.o

            
            	    When we run the section mismatch analysis on vmlinux.o we

            
            	    looses valueable information about where the mismatch was

            
            	    introduced.

            
            	    Running the analysis for each module/built-in.o file

            
            	    will tell where the mismatch happens much closer to the

            
            	    source. The drawback is that we will report the same

            
            	    mismatch at least twice.

            
            	  - Enable verbose reporting from modpost to help solving

            
            	    the section mismatches reported.


            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 || BLACKFIN

            
            	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 DEBUG_SG

            
            	bool "Debug SG table operations"

            
            	depends on DEBUG_KERNEL

            
            	help

            
            	  Enable this to turn on checks on scatter-gather tables. This can

            
            	  help find problems with drivers that do not properly initialize

            
            	  their sg tables.


            	  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 || BLACKFIN)

            
            	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


            config LATENCYTOP

            
            	bool "Latency measuring infrastructure"

            
            	select FRAME_POINTER if !MIPS

            
            	select KALLSYMS

            
            	select KALLSYMS_ALL

            
            	select STACKTRACE

            
            	select SCHEDSTATS

            
            	select SCHED_DEBUG

            
            	depends on X86 || X86_64

            
            	help

            
            	  Enable this option if you want to use the LatencyTOP tool

            
            	  to find out which userspace is blocking on what kernel operations.


            source "samples/Kconfig"

	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_WARN_DEPRECATED
	bool "Enable __deprecated logic"
	default y
	help
	Enable the __deprecated logic in the kernel build.
	Disable this to suppress the "warning: 'foo' is deprecated
	(declared at kernel/power/somefile.c:1234)" messages.

	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_SECTION_MISMATCH
	bool "Enable full Section mismatch analysis"
	default n
	help
	The section mismatch analysis checks if there are illegal
	references from one section to another section.
	Linux will during link or during runtime drop some sections
	and any use of code/data previously in these sections will
	most likely result in an oops.
	In the code functions and variables are annotated with
	__init, __devinit etc. (see full list in include/linux/init.h)
	which result in the code/data being placed in specific sections.
	The section mismatch anaylsis are always done after a full
	kernel build but enabling this options will in addition
	do the following:
	- Add the option -fno-inline-functions-called-once to gcc
	When inlining a function annotated __init in a non-init
	function we would loose the section information and thus
	the analysis would not catch the illegal reference.
	This options tell gcc to inline less but will also
	result in a larger kernel.
	- Run the section mismatch analysis for each module/built-in.o
	When we run the section mismatch analysis on vmlinux.o we
	looses valueable information about where the mismatch was
	introduced.
	Running the analysis for each module/built-in.o file
	will tell where the mismatch happens much closer to the
	source. The drawback is that we will report the same
	mismatch at least twice.
	- Enable verbose reporting from modpost to help solving
	the section mismatches reported.

	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 \|\| BLACKFIN
	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 DEBUG_SG
	bool "Debug SG table operations"
	depends on DEBUG_KERNEL
	help
	Enable this to turn on checks on scatter-gather tables. This can
	help find problems with drivers that do not properly initialize
	their sg tables.

	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 \|\| BLACKFIN)
	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

	config LATENCYTOP
	bool "Latency measuring infrastructure"
	select FRAME_POINTER if !MIPS
	select KALLSYMS
	select KALLSYMS_ALL
	select STACKTRACE
	select SCHEDSTATS
	select SCHED_DEBUG
	depends on X86 \|\| X86_64
	help
	Enable this option if you want to use the LatencyTOP tool
	to find out which userspace is blocking on what kernel operations.


	source "samples/Kconfig"