consolidate runtime testing configs

[mirror_ubuntu-zesty-kernel.git] / lib / Kconfig.debug

config PRINTK_TIME
        bool "Show timing information on printks"
        depends on PRINTK
        help
          Selecting this option causes time stamps of the printk()
          messages to be added to the output of the syslog() system
          call and at the console.

          The timestamp is always recorded internally, and exported
          to /dev/kmsg. This flag just specifies if the timestamp should
          be included, not that the timestamp is recorded.

          The behavior is also controlled by the kernel command line
          parameter printk.time=1. See Documentation/kernel-parameters.txt

config DEFAULT_MESSAGE_LOGLEVEL
        int "Default message log level (1-7)"
        range 1 7
        default "4"
        help
          Default log level for printk statements with no specified priority.

          This was hard-coded to KERN_WARNING since at least 2.6.10 but folks
          that are auditing their logs closely may want to set it to a lower
          priority.

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 FRAME_WARN
        int "Warn for stack frames larger than (needs gcc 4.4)"
        range 0 8192
        default 1024 if !64BIT
        default 2048 if 64BIT
        help
          Tell gcc to warn at build time for stack frames larger than this.
          Setting this too low will cause a lot of warnings.
          Setting it to 0 disables the warning.
          Requires gcc 4.4

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 STRIP_ASM_SYMS
        bool "Strip assembler-generated symbols during link"
        default n
        help
          Strip internal assembler-generated symbols during a link (symbols
          that look like '.Lxxx') so they don't pollute the output of
          get_wchan() and suchlike.

config READABLE_ASM
        bool "Generate readable assembler code"
        depends on DEBUG_KERNEL
        help
          Disable some compiler optimizations that tend to generate human unreadable
          assembler output. This may make the kernel slightly slower, but it helps
          to keep kernel developers who have to stare a lot at assembler listings
          sane.

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"
        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.

          For detailed documentation on the debugfs API, see
          Documentation/DocBook/filesystems.

          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"
        help
          The section mismatch analysis checks if there are illegal
          references from one section to another section.
          During linktime or runtime, some sections are dropped;
          any use of code/data previously in these sections would
          most likely result in an oops.
          In the code, functions and variables are annotated with
          __init, __cpuinit, etc. (see the full list in include/linux/init.h),
          which results in the code/data being placed in specific sections.
          The section mismatch analysis is always performed after a full
          kernel build, and enabling this option causes the following
          additional steps to occur:
          - Add the option -fno-inline-functions-called-once to gcc commands.
            When inlining a function annotated with __init in a non-init
            function, we would lose the section information and thus
            the analysis would not catch the illegal reference.
            This option tells gcc to inline less (but it does result in
            a larger kernel).
          - Run the section mismatch analysis for each module/built-in.o file.
            When we run the section mismatch analysis on vmlinux.o, we
            lose valueble information about where the mismatch was
            introduced.
            Running the analysis for each module/built-in.o file
            tells where the mismatch happens much closer to the
            source. The drawback is that the same mismatch is
            reported at least twice.
          - Enable verbose reporting from modpost in order to help resolve
            the section mismatches that are reported.

config DEBUG_KERNEL
        bool "Kernel debugging"
        help
          Say Y here if you are developing drivers or trying to debug and
          identify kernel problems.

menu "Memory Debugging"

source mm/Kconfig.debug

config DEBUG_OBJECTS
        bool "Debug object operations"
        depends on DEBUG_KERNEL
        help
          If you say Y here, additional code will be inserted into the
          kernel to track the life time of various objects and validate
          the operations on those objects.

config DEBUG_OBJECTS_SELFTEST
        bool "Debug objects selftest"
        depends on DEBUG_OBJECTS
        help
          This enables the selftest of the object debug code.

config DEBUG_OBJECTS_FREE
        bool "Debug objects in freed memory"
        depends on DEBUG_OBJECTS
        help
          This enables checks whether a k/v free operation frees an area
          which contains an object which has not been deactivated
          properly. This can make kmalloc/kfree-intensive workloads
          much slower.

config DEBUG_OBJECTS_TIMERS
        bool "Debug timer objects"
        depends on DEBUG_OBJECTS
        help
          If you say Y here, additional code will be inserted into the
          timer routines to track the life time of timer objects and
          validate the timer operations.

config DEBUG_OBJECTS_WORK
        bool "Debug work objects"
        depends on DEBUG_OBJECTS
        help
          If you say Y here, additional code will be inserted into the
          work queue routines to track the life time of work objects and
          validate the work operations.

config DEBUG_OBJECTS_RCU_HEAD
        bool "Debug RCU callbacks objects"
        depends on DEBUG_OBJECTS
        help
          Enable this to turn on debugging of RCU list heads (call_rcu() usage).

config DEBUG_OBJECTS_PERCPU_COUNTER
        bool "Debug percpu counter objects"
        depends on DEBUG_OBJECTS
        help
          If you say Y here, additional code will be inserted into the
          percpu counter routines to track the life time of percpu counter
          objects and validate the percpu counter operations.

config DEBUG_OBJECTS_ENABLE_DEFAULT
        int "debug_objects bootup default value (0-1)"
        range 0 1
        default "1"
        depends on DEBUG_OBJECTS
        help
          Debug objects boot parameter default value

config DEBUG_SLAB
        bool "Debug slab memory allocations"
        depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
        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 && !KMEMCHECK
        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 SLUB_STATS
        default n
        bool "Enable SLUB performance statistics"
        depends on SLUB && SYSFS
        help
          SLUB statistics are useful to debug SLUBs allocation behavior in
          order find ways to optimize the allocator. This should never be
          enabled for production use since keeping statistics slows down
          the allocator by a few percentage points. The slabinfo command
          supports the determination of the most active slabs to figure
          out which slabs are relevant to a particular load.
          Try running: slabinfo -DA

config HAVE_DEBUG_KMEMLEAK
        bool

config DEBUG_KMEMLEAK
        bool "Kernel memory leak detector"
        depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK
        select DEBUG_FS
        select STACKTRACE if STACKTRACE_SUPPORT
        select KALLSYMS
        select CRC32
        help
          Say Y here if you want to enable the memory leak
          detector. The memory allocation/freeing is traced in a way
          similar to the Boehm's conservative garbage collector, the
          difference being that the orphan objects are not freed but
          only shown in /sys/kernel/debug/kmemleak. Enabling this
          feature will introduce an overhead to memory
          allocations. See Documentation/kmemleak.txt for more
          details.

          Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances
          of finding leaks due to the slab objects poisoning.

          In order to access the kmemleak file, debugfs needs to be
          mounted (usually at /sys/kernel/debug).

config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
        int "Maximum kmemleak early log entries"
        depends on DEBUG_KMEMLEAK
        range 200 40000
        default 400
        help
          Kmemleak must track all the memory allocations to avoid
          reporting false positives. Since memory may be allocated or
          freed before kmemleak is initialised, an early log buffer is
          used to store these actions. If kmemleak reports "early log
          buffer exceeded", please increase this value.

config DEBUG_KMEMLEAK_TEST
        tristate "Simple test for the kernel memory leak detector"
        depends on DEBUG_KMEMLEAK && m
        help
          This option enables a module that explicitly leaks memory.

          If unsure, say N.

config DEBUG_KMEMLEAK_DEFAULT_OFF
        bool "Default kmemleak to off"
        depends on DEBUG_KMEMLEAK
        help
          Say Y here to disable kmemleak by default. It can then be enabled
          on the command line via kmemleak=on.

config DEBUG_STACK_USAGE
        bool "Stack utilization instrumentation"
        depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAG
        help
          Enables the display of the minimum amount of free stack which each
          task has ever had available in the sysrq-T and sysrq-P debug output.

          This option will slow down process creation somewhat.

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_VM_RB
        bool "Debug VM red-black trees"
        depends on DEBUG_VM
        help
          Enable this to turn on more extended checks in the virtual-memory
          system that may impact performance.

          If unsure, say N.

config DEBUG_VIRTUAL
        bool "Debug VM translations"
        depends on DEBUG_KERNEL && X86
        help
          Enable some costly sanity checks in virtual to page code. This can
          catch mistakes with virt_to_page() and friends.

          If unsure, say N.

config DEBUG_NOMMU_REGIONS
        bool "Debug the global anon/private NOMMU mapping region tree"
        depends on DEBUG_KERNEL && !MMU
        help
          This option causes the global tree of anonymous and private mapping
          regions to be regularly checked for invalid topology.

config DEBUG_MEMORY_INIT
        bool "Debug memory initialisation" if EXPERT
        default !EXPERT
        help
          Enable this for additional checks during memory initialisation.
          The sanity checks verify aspects of the VM such as the memory model
          and other information provided by the architecture. Verbose
          information will be printed at KERN_DEBUG loglevel depending
          on the mminit_loglevel= command-line option.

          If unsure, say Y

config MEMORY_NOTIFIER_ERROR_INJECT
        tristate "Memory hotplug notifier error injection module"
        depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION
        help
          This option provides the ability to inject artificial errors to
          memory hotplug notifier chain callbacks.  It is controlled through
          debugfs interface under /sys/kernel/debug/notifier-error-inject/memory

          If the notifier call chain should be failed with some events
          notified, write the error code to "actions/<notifier event>/error".

          Example: Inject memory hotplug offline error (-12 == -ENOMEM)

          # cd /sys/kernel/debug/notifier-error-inject/memory
          # echo -12 > actions/MEM_GOING_OFFLINE/error
          # echo offline > /sys/devices/system/memory/memoryXXX/state
          bash: echo: write error: Cannot allocate memory

          To compile this code as a module, choose M here: the module will
          be called memory-notifier-error-inject.

          If unsure, say N.

config DEBUG_PER_CPU_MAPS
        bool "Debug access to per_cpu maps"
        depends on DEBUG_KERNEL
        depends on SMP
        help
          Say Y to verify that the per_cpu map being accessed has
          been set up. This adds a fair amount of code to kernel memory
          and decreases performance.

          Say N if unsure.

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 HAVE_DEBUG_STACKOVERFLOW
        bool

config DEBUG_STACKOVERFLOW
        bool "Check for stack overflows"
        depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW
        ---help---
          Say Y here if you want to check for overflows of kernel, IRQ
          and exception stacks (if your archicture uses them). This
          option will show detailed messages if free stack space drops
          below a certain limit.

          These kinds of bugs usually occur when call-chains in the
          kernel get too deep, especially when interrupts are
          involved.

          Use this in cases where you see apparently random memory
          corruption, especially if it appears in 'struct thread_info'

          If in doubt, say "N".

source "lib/Kconfig.kmemcheck"

endmenu # "Memory Debugging"

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 LOCKUP_DETECTOR
        bool "Detect Hard and Soft Lockups"
        depends on DEBUG_KERNEL && !S390
        help
          Say Y here to enable the kernel to act as a watchdog to detect
          hard and soft lockups.

          Softlockups are bugs that cause the kernel to loop in kernel
          mode for more than 20 seconds, without giving other tasks a
          chance to run.  The current stack trace is displayed upon
          detection and the system will stay locked up.

          Hardlockups are bugs that cause the CPU to loop in kernel mode
          for more than 10 seconds, without letting other interrupts have a
          chance to run.  The current stack trace is displayed upon detection
          and the system will stay locked up.

          The overhead should be minimal.  A periodic hrtimer runs to
          generate interrupts and kick the watchdog task every 4 seconds.
          An NMI is generated every 10 seconds or so to check for hardlockups.

          The frequency of hrtimer and NMI events and the soft and hard lockup
          thresholds can be controlled through the sysctl watchdog_thresh.

config HARDLOCKUP_DETECTOR
        def_bool y
        depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG
        depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI

config BOOTPARAM_HARDLOCKUP_PANIC
        bool "Panic (Reboot) On Hard Lockups"
        depends on HARDLOCKUP_DETECTOR
        help
          Say Y here to enable the kernel to panic on "hard lockups",
          which are bugs that cause the kernel to loop in kernel
          mode with interrupts disabled for more than 10 seconds (configurable
          using the watchdog_thresh sysctl).

          Say N if unsure.

config BOOTPARAM_HARDLOCKUP_PANIC_VALUE
        int
        depends on HARDLOCKUP_DETECTOR
        range 0 1
        default 0 if !BOOTPARAM_HARDLOCKUP_PANIC
        default 1 if BOOTPARAM_HARDLOCKUP_PANIC

config BOOTPARAM_SOFTLOCKUP_PANIC
        bool "Panic (Reboot) On Soft Lockups"
        depends on LOCKUP_DETECTOR
        help
          Say Y here to enable the kernel to panic on "soft lockups",
          which are bugs that cause the kernel to loop in kernel
          mode for more than 20 seconds (configurable using the watchdog_thresh
          sysctl), without giving other tasks a chance to run.

          The panic can be used in combination with panic_timeout,
          to cause the system to reboot automatically after a
          lockup has been detected. This feature is useful for
          high-availability systems that have uptime guarantees and
          where a lockup must be resolved ASAP.

          Say N if unsure.

config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
        int
        depends on LOCKUP_DETECTOR
        range 0 1
        default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
        default 1 if BOOTPARAM_SOFTLOCKUP_PANIC

config PANIC_ON_OOPS
        bool "Panic on Oops"
        help
          Say Y here to enable the kernel to panic when it oopses. This
          has the same effect as setting oops=panic on the kernel command
          line.

          This feature is useful to ensure that the kernel does not do
          anything erroneous after an oops which could result in data
          corruption or other issues.

          Say N if unsure.

config PANIC_ON_OOPS_VALUE
        int
        range 0 1
        default 0 if !PANIC_ON_OOPS
        default 1 if PANIC_ON_OOPS

config DETECT_HUNG_TASK
        bool "Detect Hung Tasks"
        depends on DEBUG_KERNEL
        default LOCKUP_DETECTOR
        help
          Say Y here to enable the kernel to detect "hung tasks",
          which are bugs that cause the task to be stuck in
          uninterruptible "D" state indefinitiley.

          When a hung task is detected, the kernel will print the
          current stack trace (which you should report), but the
          task will stay in uninterruptible state. If lockdep is
          enabled then all held locks will also be reported. This
          feature has negligible overhead.

config DEFAULT_HUNG_TASK_TIMEOUT
        int "Default timeout for hung task detection (in seconds)"
        depends on DETECT_HUNG_TASK
        default 120
        help
          This option controls the default timeout (in seconds) used
          to determine when a task has become non-responsive and should
          be considered hung.

          It can be adjusted at runtime via the kernel.hung_task_timeout_secs
          sysctl or by writing a value to
          /proc/sys/kernel/hung_task_timeout_secs.

          A timeout of 0 disables the check.  The default is two minutes.
          Keeping the default should be fine in most cases.

config BOOTPARAM_HUNG_TASK_PANIC
        bool "Panic (Reboot) On Hung Tasks"
        depends on DETECT_HUNG_TASK
        help
          Say Y here to enable the kernel to panic on "hung tasks",
          which are bugs that cause the kernel to leave a task stuck
          in uninterruptible "D" state.

          The panic can be used in combination with panic_timeout,
          to cause the system to reboot automatically after a
          hung task has been detected. This feature is useful for
          high-availability systems that have uptime guarantees and
          where a hung tasks must be resolved ASAP.

          Say N if unsure.

config BOOTPARAM_HUNG_TASK_PANIC_VALUE
        int
        depends on DETECT_HUNG_TASK
        range 0 1
        default 0 if !BOOTPARAM_HUNG_TASK_PANIC
        default 1 if BOOTPARAM_HUNG_TASK_PANIC

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_PREEMPT
        bool "Debug preemptible kernel"
        depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
        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
        select UNINLINE_SPIN_UNLOCK
        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_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
        select TRACE_IRQFLAGS
        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 !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE
        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

         This also enables lock events required by "perf lock",
         subcommand of perf.
         If you want to use "perf lock", you also need to turn on
         CONFIG_EVENT_TRACING.

         CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.
         (CONFIG_LOCKDEP defines "acquire" and "release" events.)

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
        bool
        help
          Enables hooks to interrupt enabling and disabling for
          either tracing or lock debugging.

config DEBUG_ATOMIC_SLEEP
        bool "Sleep inside atomic section checking"
        select PREEMPT_COUNT
        depends on DEBUG_KERNEL
        help
          If you say Y here, various routines which may sleep will become very
          noisy if they are called inside atomic sections: when a spinlock is
          held, inside an rcu read side critical section, inside preempt disabled
          sections, inside an interrupt, etc...

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 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 HAVE_DEBUG_BUGVERBOSE
        bool

config DEBUG_BUGVERBOSE
        bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT
        depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)
        default y
        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_INFO_REDUCED
        bool "Reduce debugging information"
        depends on DEBUG_INFO
        help
          If you say Y here gcc is instructed to generate less debugging
          information for structure types. This means that tools that
          need full debugging information (like kgdb or systemtap) won't
          be happy. But if you merely need debugging information to
          resolve line numbers there is no loss. Advantage is that
          build directory object sizes shrink dramatically over a full
          DEBUG_INFO build and compile times are reduced too.
          Only works with newer gcc versions.

config DEBUG_WRITECOUNT
        bool "Debug filesystem writers count"
        depends on DEBUG_KERNEL
        help
          Enable this to catch wrong use of the writers count in struct
          vfsmount.  This will increase the size of each file struct by
          32 bits.

          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 DEBUG_NOTIFIERS
        bool "Debug notifier call chains"
        depends on DEBUG_KERNEL
        help
          Enable this to turn on sanity checking for notifier call chains.
          This is most useful for kernel developers to make sure that
          modules properly unregister themselves from notifier chains.
          This is a relatively cheap check but if you care about maximum
          performance, say N.

config DEBUG_CREDENTIALS
        bool "Debug credential management"
        depends on DEBUG_KERNEL
        help
          Enable this to turn on some debug checking for credential
          management.  The additional code keeps track of the number of
          pointers from task_structs to any given cred struct, and checks to
          see that this number never exceeds the usage count of the cred
          struct.

          Furthermore, if SELinux is enabled, this also checks that the
          security pointer in the cred struct is never seen to be invalid.

          If unsure, say N.

#
# Select this config option from the architecture Kconfig, if it
# is preferred to always offer frame pointers as a config
# option on the architecture (regardless of KERNEL_DEBUG):
#
config ARCH_WANT_FRAME_POINTERS
        bool
        help

config FRAME_POINTER
        bool "Compile the kernel with frame pointers"
        depends on DEBUG_KERNEL && \
                (CRIS || M68K || FRV || UML || \
                 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \
                ARCH_WANT_FRAME_POINTERS
        default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
        help
          If you say Y here the resulting kernel image will be slightly
          larger and slower, but it gives very useful debugging information
          in case of kernel bugs. (precise oopses/stacktraces/warnings)

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 LOCKUP_DETECTOR to detect
          what it believes to be lockup conditions.

menu "RCU Debugging"

config PROVE_RCU
        bool "RCU debugging: prove RCU correctness"
        depends on PROVE_LOCKING
        default n
        help
         This feature enables lockdep extensions that check for correct
         use of RCU APIs.  This is currently under development.  Say Y
         if you want to debug RCU usage or help work on the PROVE_RCU
         feature.

         Say N if you are unsure.

config PROVE_RCU_REPEATEDLY
        bool "RCU debugging: don't disable PROVE_RCU on first splat"
        depends on PROVE_RCU
        default n
        help
         By itself, PROVE_RCU will disable checking upon issuing the
         first warning (or "splat").  This feature prevents such
         disabling, allowing multiple RCU-lockdep warnings to be printed
         on a single reboot.

         Say Y to allow multiple RCU-lockdep warnings per boot.

         Say N if you are unsure.

config PROVE_RCU_DELAY
        bool "RCU debugging: preemptible RCU race provocation"
        depends on DEBUG_KERNEL && PREEMPT_RCU
        default n
        help
         There is a class of races that involve an unlikely preemption
         of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
         been set to INT_MIN.  This feature inserts a delay at that
         point to increase the probability of these races.

         Say Y to increase probability of preemption of __rcu_read_unlock().

         Say N if you are unsure.

config SPARSE_RCU_POINTER
        bool "RCU debugging: sparse-based checks for pointer usage"
        default n
        help
         This feature enables the __rcu sparse annotation for
         RCU-protected pointers.  This annotation will cause sparse
         to flag any non-RCU used of annotated pointers.  This can be
         helpful when debugging RCU usage.  Please note that this feature
         is not intended to enforce code cleanliness; it is instead merely
         a debugging aid.

         Say Y to make sparse flag questionable use of RCU-protected pointers

         Say N if you are unsure.

config RCU_TORTURE_TEST
        tristate "torture tests for RCU"
        depends on DEBUG_KERNEL
        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 Y here if you want RCU torture tests to be built into
          the kernel.
          Say M if you want the RCU torture tests to build as a module.
          Say N if you are unsure.

config RCU_TORTURE_TEST_RUNNABLE
        bool "torture tests for RCU runnable by default"
        depends on RCU_TORTURE_TEST = y
        default n
        help
          This option provides a way to build the RCU torture tests
          directly into the kernel without them starting up at boot
          time.  You can use /proc/sys/kernel/rcutorture_runnable
          to manually override this setting.  This /proc file is
          available only when the RCU torture tests have been built
          into the kernel.

          Say Y here if you want the RCU torture tests to start during
          boot (you probably don't).
          Say N here if you want the RCU torture tests to start only
          after being manually enabled via /proc.

config RCU_CPU_STALL_TIMEOUT
        int "RCU CPU stall timeout in seconds"
        depends on RCU_STALL_COMMON
        range 3 300
        default 21
        help
          If a given RCU grace period extends more than the specified
          number of seconds, a CPU stall warning is printed.  If the
          RCU grace period persists, additional CPU stall warnings are
          printed at more widely spaced intervals.

config RCU_CPU_STALL_VERBOSE
        bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
        depends on TREE_PREEMPT_RCU
        default y
        help
          This option causes RCU to printk detailed per-task information
          for any tasks that are stalling the current RCU grace period.

          Say N if you are unsure.

          Say Y if you want to enable such checks.

config RCU_CPU_STALL_INFO
        bool "Print additional diagnostics on RCU CPU stall"
        depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
        default n
        help
          For each stalled CPU that is aware of the current RCU grace
          period, print out additional per-CPU diagnostic information
          regarding scheduling-clock ticks, idle state, and,
          for RCU_FAST_NO_HZ kernels, idle-entry state.

          Say N if you are unsure.

          Say Y if you want to enable such diagnostics.

config RCU_TRACE
        bool "Enable tracing for RCU"
        depends on DEBUG_KERNEL
        select TRACE_CLOCK
        help
          This option provides tracing in RCU which presents stats
          in debugfs for debugging RCU implementation.

          Say Y here if you want to enable RCU tracing
          Say N if you are unsure.

endmenu # "RCU Debugging"

config DEBUG_BLOCK_EXT_DEVT
        bool "Force extended block device numbers and spread them"
        depends on DEBUG_KERNEL
        depends on BLOCK
        default n
        help
          BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON
          SOME DISTRIBUTIONS.  DO NOT ENABLE THIS UNLESS YOU KNOW WHAT
          YOU ARE DOING.  Distros, please enable this and fix whatever
          is broken.

          Conventionally, block device numbers are allocated from
          predetermined contiguous area.  However, extended block area
          may introduce non-contiguous block device numbers.  This
          option forces most block device numbers to be allocated from
          the extended space and spreads them to discover kernel or
          userland code paths which assume predetermined contiguous
          device number allocation.

          Note that turning on this debug option shuffles all the
          device numbers for all IDE and SCSI devices including libata
          ones, so root partition specified using device number
          directly (via rdev or root=MAJ:MIN) won't work anymore.
          Textual device names (root=/dev/sdXn) will continue to work.

          Say N if you are unsure.

config DEBUG_FORCE_WEAK_PER_CPU
        bool "Force weak per-cpu definitions"
        depends on DEBUG_KERNEL
        help
          s390 and alpha require percpu variables in modules to be
          defined weak to work around addressing range issue which
          puts the following two restrictions on percpu variable
          definitions.

          1. percpu symbols must be unique whether static or not
          2. percpu variables can't be defined inside a function

          To ensure that generic code follows the above rules, this
          option forces all percpu variables to be defined as weak.

config NOTIFIER_ERROR_INJECTION
        tristate "Notifier error injection"
        depends on DEBUG_KERNEL
        select DEBUG_FS
        help
          This option provides the ability to inject artificial errors to
          specified notifier chain callbacks. It is useful to test the error
          handling of notifier call chain failures.

          Say N if unsure.

config CPU_NOTIFIER_ERROR_INJECT
        tristate "CPU notifier error injection module"
        depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION
        help
          This option provides a kernel module that can be used to test
          the error handling of the cpu notifiers by injecting artificial
          errors to CPU notifier chain callbacks.  It is controlled through
          debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu

          If the notifier call chain should be failed with some events
          notified, write the error code to "actions/<notifier event>/error".

          Example: Inject CPU offline error (-1 == -EPERM)

          # cd /sys/kernel/debug/notifier-error-inject/cpu
          # echo -1 > actions/CPU_DOWN_PREPARE/error
          # echo 0 > /sys/devices/system/cpu/cpu1/online
          bash: echo: write error: Operation not permitted

          To compile this code as a module, choose M here: the module will
          be called cpu-notifier-error-inject.

          If unsure, say N.

config PM_NOTIFIER_ERROR_INJECT
        tristate "PM notifier error injection module"
        depends on PM && NOTIFIER_ERROR_INJECTION
        default m if PM_DEBUG
        help
          This option provides the ability to inject artificial errors to
          PM notifier chain callbacks.  It is controlled through debugfs
          interface /sys/kernel/debug/notifier-error-inject/pm

          If the notifier call chain should be failed with some events
          notified, write the error code to "actions/<notifier event>/error".

          Example: Inject PM suspend error (-12 = -ENOMEM)

          # cd /sys/kernel/debug/notifier-error-inject/pm/
          # echo -12 > actions/PM_SUSPEND_PREPARE/error
          # echo mem > /sys/power/state
          bash: echo: write error: Cannot allocate memory

          To compile this code as a module, choose M here: the module will
          be called pm-notifier-error-inject.

          If unsure, say N.

config OF_RECONFIG_NOTIFIER_ERROR_INJECT
        tristate "OF reconfig notifier error injection module"
        depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION
        help
          This option provides the ability to inject artificial errors to
          OF reconfig notifier chain callbacks.  It is controlled
          through debugfs interface under
          /sys/kernel/debug/notifier-error-inject/OF-reconfig/

          If the notifier call chain should be failed with some events
          notified, write the error code to "actions/<notifier event>/error".

          To compile this code as a module, choose M here: the module will
          be called of-reconfig-notifier-error-inject.

          If unsure, say N.

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
        depends on SLAB || SLUB
        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 && BLOCK
        help
          Provide fault-injection capability for disk IO.

config FAIL_IO_TIMEOUT
        bool "Fault-injection capability for faking disk interrupts"
        depends on FAULT_INJECTION && BLOCK
        help
          Provide fault-injection capability on end IO handling. This
          will make the block layer "forget" an interrupt as configured,
          thus exercising the error handling.

          Only works with drivers that use the generic timeout handling,
          for others it wont do anything.

config FAIL_MMC_REQUEST
        bool "Fault-injection capability for MMC IO"
        select DEBUG_FS
        depends on FAULT_INJECTION && MMC
        help
          Provide fault-injection capability for MMC IO.
          This will make the mmc core return data errors. This is
          useful to test the error handling in the mmc block device
          and to test how the mmc host driver handles retries from
          the block device.

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 if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
        help
          Provide stacktrace filter for fault-injection capabilities

config LATENCYTOP
        bool "Latency measuring infrastructure"
        depends on HAVE_LATENCYTOP_SUPPORT
        depends on DEBUG_KERNEL
        depends on STACKTRACE_SUPPORT
        depends on PROC_FS
        select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND
        select KALLSYMS
        select KALLSYMS_ALL
        select STACKTRACE
        select SCHEDSTATS
        select SCHED_DEBUG
        help
          Enable this option if you want to use the LatencyTOP tool
          to find out which userspace is blocking on what kernel operations.

config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
        bool

config DEBUG_STRICT_USER_COPY_CHECKS
        bool "Strict user copy size checks"
        depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
        depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
        help
          Enabling this option turns a certain set of sanity checks for user
          copy operations into compile time failures.

          The copy_from_user() etc checks are there to help test if there
          are sufficient security checks on the length argument of
          the copy operation, by having gcc prove that the argument is
          within bounds.

          If unsure, say N.

source kernel/trace/Kconfig

menu "Runtime Testing"

config LKDTM
        tristate "Linux Kernel Dump Test Tool Module"
        depends on DEBUG_FS
        depends on BLOCK
        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
        Documentation/fault-injection/provoke-crashes.txt

config TEST_LIST_SORT
        bool "Linked list sorting test"
        depends on DEBUG_KERNEL
        help
          Enable this to turn on 'list_sort()' function test. This test is
          executed only once during system boot, so affects only boot time.

          If unsure, say N.

config KPROBES_SANITY_TEST
        bool "Kprobes sanity tests"
        depends on DEBUG_KERNEL
        depends on KPROBES
        default n
        help
          This option provides for testing basic kprobes functionality on
          boot. A sample kprobe, jprobe and kretprobe are inserted and
          verified for functionality.

          Say N if you are unsure.

config BACKTRACE_SELF_TEST
        tristate "Self test for the backtrace code"
        depends on DEBUG_KERNEL
        default n
        help
          This option provides a kernel module that can be used to test
          the kernel stack backtrace code. This option is not useful
          for distributions or general kernels, but only for kernel
          developers working on architecture code.

          Note that if you want to also test saved backtraces, you will
          have to enable STACKTRACE as well.

          Say N if you are unsure.

config RBTREE_TEST
        tristate "Red-Black tree test"
        depends on m && DEBUG_KERNEL
        help
          A benchmark measuring the performance of the rbtree library.
          Also includes rbtree invariant checks.

config INTERVAL_TREE_TEST
        tristate "Interval tree test"
        depends on m && DEBUG_KERNEL
        help
          A benchmark measuring the performance of the interval tree library

config ATOMIC64_SELFTEST
        bool "Perform an atomic64_t self-test at boot"
        help
          Enable this option to test the atomic64_t functions at boot.

          If unsure, say N.

config ASYNC_RAID6_TEST
        tristate "Self test for hardware accelerated raid6 recovery"
        depends on ASYNC_RAID6_RECOV
        select ASYNC_MEMCPY
        ---help---
          This is a one-shot self test that permutes through the
          recovery of all the possible two disk failure scenarios for a
          N-disk array.  Recovery is performed with the asynchronous
          raid6 recovery routines, and will optionally use an offload
          engine if one is available.

          If unsure, say N.

config TEST_STRING_HELPERS
        tristate "Test functions located in the string_helpers module at runtime"

config TEST_KSTRTOX
        tristate "Test kstrto*() family of functions at runtime"

endmenu # runtime tests

config PROVIDE_OHCI1394_DMA_INIT
        bool "Remote debugging over FireWire early on boot"
        depends on PCI && X86
        help
          If you want to debug problems which hang or crash the kernel early
          on boot and the crashing machine has a FireWire port, you can use
          this feature to remotely access the memory of the crashed machine
          over FireWire. This employs remote DMA as part of the OHCI1394
          specification which is now the standard for FireWire controllers.

          With remote DMA, you can monitor the printk buffer remotely using
          firescope and access all memory below 4GB using fireproxy from gdb.
          Even controlling a kernel debugger is possible using remote DMA.

          Usage:

          If ohci1394_dma=early is used as boot parameter, it will initialize
          all OHCI1394 controllers which are found in the PCI config space.

          As all changes to the FireWire bus such as enabling and disabling
          devices cause a bus reset and thereby disable remote DMA for all
          devices, be sure to have the cable plugged and FireWire enabled on
          the debugging host before booting the debug target for debugging.

          This code (~1k) is freed after boot. By then, the firewire stack
          in charge of the OHCI-1394 controllers should be used instead.

          See Documentation/debugging-via-ohci1394.txt for more information.

config FIREWIRE_OHCI_REMOTE_DMA
        bool "Remote debugging over FireWire with firewire-ohci"
        depends on FIREWIRE_OHCI
        help
          This option lets you use the FireWire bus for remote debugging
          with help of the firewire-ohci driver. It enables unfiltered
          remote DMA in firewire-ohci.
          See Documentation/debugging-via-ohci1394.txt for more information.

          If unsure, say N.

config BUILD_DOCSRC
        bool "Build targets in Documentation/ tree"
        depends on HEADERS_CHECK
        help
          This option attempts to build objects from the source files in the
          kernel Documentation/ tree.

          Say N if you are unsure.

config DYNAMIC_DEBUG
        bool "Enable dynamic printk() support"
        default n
        depends on PRINTK
        depends on DEBUG_FS
        help

          Compiles debug level messages into the kernel, which would not
          otherwise be available at runtime. These messages can then be
          enabled/disabled based on various levels of scope - per source file,
          function, module, format string, and line number. This mechanism
          implicitly compiles in all pr_debug() and dev_dbg() calls, which
          enlarges the kernel text size by about 2%.

          If a source file is compiled with DEBUG flag set, any
          pr_debug() calls in it are enabled by default, but can be
          disabled at runtime as below.  Note that DEBUG flag is
          turned on by many CONFIG_*DEBUG* options.

          Usage:

          Dynamic debugging is controlled via the 'dynamic_debug/control' file,
          which is contained in the 'debugfs' filesystem. Thus, the debugfs
          filesystem must first be mounted before making use of this feature.
          We refer the control file as: <debugfs>/dynamic_debug/control. This
          file contains a list of the debug statements that can be enabled. The
          format for each line of the file is:

                filename:lineno [module]function flags format

          filename : source file of the debug statement
          lineno : line number of the debug statement
          module : module that contains the debug statement
          function : function that contains the debug statement
          flags : '=p' means the line is turned 'on' for printing
          format : the format used for the debug statement

          From a live system:

                nullarbor:~ # cat <debugfs>/dynamic_debug/control
                # filename:lineno [module]function flags format
                fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012"
                fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012"
                fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012"

          Example usage:

                // enable the message at line 1603 of file svcsock.c
                nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' >
                                                <debugfs>/dynamic_debug/control

                // enable all the messages in file svcsock.c
                nullarbor:~ # echo -n 'file svcsock.c +p' >
                                                <debugfs>/dynamic_debug/control

                // enable all the messages in the NFS server module
                nullarbor:~ # echo -n 'module nfsd +p' >
                                                <debugfs>/dynamic_debug/control

                // enable all 12 messages in the function svc_process()
                nullarbor:~ # echo -n 'func svc_process +p' >
                                                <debugfs>/dynamic_debug/control

                // disable all 12 messages in the function svc_process()
                nullarbor:~ # echo -n 'func svc_process -p' >
                                                <debugfs>/dynamic_debug/control

          See Documentation/dynamic-debug-howto.txt for additional information.

config DMA_API_DEBUG
        bool "Enable debugging of DMA-API usage"
        depends on HAVE_DMA_API_DEBUG
        help
          Enable this option to debug the use of the DMA API by device drivers.
          With this option you will be able to detect common bugs in device
          drivers like double-freeing of DMA mappings or freeing mappings that
          were never allocated.
          This option causes a performance degredation.  Use only if you want
          to debug device drivers. If unsure, say N.

source "samples/Kconfig"

source "lib/Kconfig.kgdb"