menu "printk and dmesg options"config PRINTK_TIMEbool "Show timing information on printks"depends on PRINTKhelpSelecting this option causes time stamps of the printk()messages to be added to the output of the syslog() systemcall and at the console.The timestamp is always recorded internally, and exportedto /dev/kmsg. This flag just specifies if the timestamp shouldbe included, not that the timestamp is recorded.The behavior is also controlled by the kernel command lineparameter printk.time=1. See Documentation/kernel-parameters.txtconfig MESSAGE_LOGLEVEL_DEFAULTint "Default message log level (1-7)"range 1 7default "4"helpDefault log level for printk statements with no specified priority.This was hard-coded to KERN_WARNING since at least 2.6.10 but folksthat are auditing their logs closely may want to set it to a lowerpriority.config BOOT_PRINTK_DELAYbool "Delay each boot printk message by N milliseconds"depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAYhelpThis build option allows you to read kernel boot messagesby inserting a short delay after each one. The delay isspecified in milliseconds on the kernel command line,using "boot_delay=N".It is likely that you would also need to use "lpj=M" to presetthe "loops per jiffie" value.See a previous boot log for the "lpj" value to use for yoursystem, 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 detectwhat it believes to be lockup conditions.config DYNAMIC_DEBUGbool "Enable dynamic printk() support"default ndepends on PRINTKdepends on DEBUG_FShelpCompiles debug level messages into the kernel, which would nototherwise be available at runtime. These messages can then beenabled/disabled based on various levels of scope - per source file,function, module, format string, and line number. This mechanismimplicitly compiles in all pr_debug() and dev_dbg() calls, whichenlarges the kernel text size by about 2%.If a source file is compiled with DEBUG flag set, anypr_debug() calls in it are enabled by default, but can bedisabled at runtime as below. Note that DEBUG flag isturned 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 debugfsfilesystem must first be mounted before making use of this feature.We refer the control file as: <debugfs>/dynamic_debug/control. Thisfile contains a list of the debug statements that can be enabled. Theformat for each line of the file is:filename:lineno [module]function flags formatfilename : source file of the debug statementlineno : line number of the debug statementmodule : module that contains the debug statementfunction : function that contains the debug statementflags : '=p' means the line is turned 'on' for printingformat : the format used for the debug statementFrom a live system:nullarbor:~ # cat <debugfs>/dynamic_debug/control# filename:lineno [module]function flags formatfs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:040円freeing040円%p012円"fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:040円nr_events040円too040円high012円"fs/aio.c:1770 [aio]sys_io_cancel =_ "calling040円cancel012円"Example usage:// enable the message at line 1603 of file svcsock.cnullarbor:~ # echo -n 'file svcsock.c line 1603 +p' ><debugfs>/dynamic_debug/control// enable all the messages in file svcsock.cnullarbor:~ # echo -n 'file svcsock.c +p' ><debugfs>/dynamic_debug/control// enable all the messages in the NFS server modulenullarbor:~ # 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/controlSee Documentation/dynamic-debug-howto.txt for additional information.endmenu # "printk and dmesg options"menu "Compile-time checks and compiler options"config DEBUG_INFObool "Compile the kernel with debug info"depends on DEBUG_KERNEL && !COMPILE_TESThelpIf you say Y here the resulting kernel image will includedebugging info resulting in a larger kernel image.This adds debug symbols to the kernel and modules (gcc -g), andis needed if you intend to use kernel crashdump or binary objecttools 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_REDUCEDbool "Reduce debugging information"depends on DEBUG_INFOhelpIf you say Y here gcc is instructed to generate less debugginginformation for structure types. This means that tools thatneed full debugging information (like kgdb or systemtap) won'tbe happy. But if you merely need debugging information toresolve line numbers there is no loss. Advantage is thatbuild directory object sizes shrink dramatically over a fullDEBUG_INFO build and compile times are reduced too.Only works with newer gcc versions.config DEBUG_INFO_SPLITbool "Produce split debuginfo in .dwo files"depends on DEBUG_INFOhelpGenerate debug info into separate .dwo files. This significantlyreduces the build directory size for builds with DEBUG_INFO,because it stores the information only once on disk in .dwofiles instead of multiple times in object files and executables.In addition the debug information is also compressed.Requires recent gcc (4.7+) and recent gdb/binutils.Any tool that packages or reads debug information would needto know about the .dwo files and include them.Incompatible with older versions of ccache.config DEBUG_INFO_DWARF4bool "Generate dwarf4 debuginfo"depends on DEBUG_INFOhelpGenerate dwarf4 debug info. This requires recent versionsof gcc and gdb. It makes the debug information larger.But it significantly improves the success of resolvingvariables in gdb on optimized code.config GDB_SCRIPTSbool "Provide GDB scripts for kernel debugging"depends on DEBUG_INFOhelpThis creates the required links to GDB helper scripts in thebuild directory. If you load vmlinux into gdb, the helperscripts will be automatically imported by gdb as well, andadditional functions are available to analyze a Linux kernelinstance. See Documentation/gdb-kernel-debugging.txt for furtherdetails.config ENABLE_WARN_DEPRECATEDbool "Enable __deprecated logic"default yhelpEnable 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_CHECKbool "Enable __must_check logic"default yhelpEnable the __must_check logic in the kernel build. Disable this tosuppress the "warning: ignoring return value of 'foo', declared withattribute warn_unused_result" messages.config FRAME_WARNint "Warn for stack frames larger than (needs gcc 4.4)"range 0 8192default 1024 if !64BITdefault 2048 if 64BIThelpTell 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 4.4config STRIP_ASM_SYMSbool "Strip assembler-generated symbols during link"default nhelpStrip internal assembler-generated symbols during a link (symbolsthat look like '.Lxxx') so they don't pollute the output ofget_wchan() and suchlike.config READABLE_ASMbool "Generate readable assembler code"depends on DEBUG_KERNELhelpDisable some compiler optimizations that tend to generate human unreadableassembler output. This may make the kernel slightly slower, but it helpsto keep kernel developers who have to stare a lot at assembler listingssane.config UNUSED_SYMBOLSbool "Enable unused/obsolete exported symbols"default y if X86helpUnused but exported symbols make the kernel needlessly bigger. Forthat reason most of these unused exports will soon be removed. Thisoption is provided temporarily to provide a transition period in casesome external kernel module needs one of these symbols anyway. If youencounter such a case in your module, consider if you are actuallyusing the right API. (rationale: since nobody in the kernel is usingthis in a module, there is a pretty good chance it's actually thewrong interface to use). If you really need the symbol, please send amail to the linux kernel mailing list mentioning the symbol and whyyou really need it, and what the merge plan to the mainline kernel foryour module is.config PAGE_OWNERbool "Track page owner"depends on DEBUG_KERNEL && STACKTRACE_SUPPORTselect DEBUG_FSselect STACKTRACEselect PAGE_EXTENSIONhelpThis keeps track of what call chain is the owner of a page, mayhelp to find bare alloc_page(s) leaks. Even if you include thisfeature on your build, it is disabled in default. You should pass"page_owner=on" to boot parameter in order to enable it. Eatsa fair amount of memory if enabled. See tools/vm/page_owner_sort.cfor user-space helper.If unsure, say N.config DEBUG_FSbool "Debug Filesystem"helpdebugfs is a virtual file system that kernel developers use to putdebugging files into. Enable this option to be able to read andwrite to these files.For detailed documentation on the debugfs API, seeDocumentation/DocBook/filesystems.If unsure, say N.config HEADERS_CHECKbool "Run 'make headers_check' when building vmlinux"depends on !UMLhelpThis option will extract the user-visible kernel headers wheneverbuilding the kernel, and will run basic sanity checks on them toensure that exported files do not attempt to include files whichwere not exported, etc.If you're making modifications to header files which arerelevant for userspace, say 'Y', and check the headersexported to $(INSTALL_HDR_PATH) (usually 'usr/include' inyour build tree), to make sure they're suitable.config DEBUG_SECTION_MISMATCHbool "Enable full Section mismatch analysis"helpThe section mismatch analysis checks if there are illegalreferences from one section to another section.During linktime or runtime, some sections are dropped;any use of code/data previously in these sections wouldmost likely result in an oops.In the code, functions and variables are annotated with__init,, 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 fullkernel build, and enabling this option causes the followingadditional steps to occur:- Add the option -fno-inline-functions-called-once to gcc commands.When inlining a function annotated with __init in a non-initfunction, we would lose the section information and thusthe analysis would not catch the illegal reference.This option tells gcc to inline less (but it does result ina larger kernel).- Run the section mismatch analysis for each module/built-in.o file.When we run the section mismatch analysis on vmlinux.o, welose valueble information about where the mismatch wasintroduced.Running the analysis for each module/built-in.o filetells where the mismatch happens much closer to thesource. The drawback is that the same mismatch isreported at least twice.- Enable verbose reporting from modpost in order to help resolvethe section mismatches that are reported.## 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_POINTERSboolhelpconfig FRAME_POINTERbool "Compile the kernel with frame pointers"depends on DEBUG_KERNEL && \(CRIS || M68K || FRV || UML || \AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ARCH_WANT_FRAME_POINTERSdefault y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERShelpIf you say Y here the resulting kernel image will be slightlylarger and slower, but it gives very useful debugging informationin case of kernel bugs. (precise oopses/stacktraces/warnings)config DEBUG_FORCE_WEAK_PER_CPUbool "Force weak per-cpu definitions"depends on DEBUG_KERNELhelps390 and alpha require percpu variables in modules to bedefined weak to work around addressing range issue whichputs the following two restrictions on percpu variabledefinitions.1. percpu symbols must be unique whether static or not2. percpu variables can't be defined inside a functionTo ensure that generic code follows the above rules, thisoption forces all percpu variables to be defined as weak.endmenu # "Compiler options"config MAGIC_SYSRQbool "Magic SysRq key"depends on !UMLhelpIf you say Y here, you will have some control over the system evenif the system crashes for example during kernel debugging (e.g., youwill be able to flush the buffer cache to disk, reboot the systemimmediately or dump some status information). This is accomplishedby pressing various keys while holding SysRq (Alt+PrintScreen). Italso works on a serial console (on PC hardware at least), if yousend a BREAK and then within 5 seconds a command keypress. Thekeys are documented in <file:Documentation/sysrq.txt>. Don't say Yunless you really know what this hack does.config MAGIC_SYSRQ_DEFAULT_ENABLEhex "Enable magic SysRq key functions by default"depends on MAGIC_SYSRQdefault 0x1helpSpecifies which SysRq key functions are enabled by default.This may be set to 1 or 0 to enable or disable them all, orto a bitmask as described in Documentation/sysrq.txt.config DEBUG_KERNELbool "Kernel debugging"helpSay Y here if you are developing drivers or trying to debug andidentify kernel problems.menu "Memory Debugging"source mm/Kconfig.debugconfig DEBUG_OBJECTSbool "Debug object operations"depends on DEBUG_KERNELhelpIf you say Y here, additional code will be inserted into thekernel to track the life time of various objects and validatethe operations on those objects.config DEBUG_OBJECTS_SELFTESTbool "Debug objects selftest"depends on DEBUG_OBJECTShelpThis enables the selftest of the object debug code.config DEBUG_OBJECTS_FREEbool "Debug objects in freed memory"depends on DEBUG_OBJECTShelpThis enables checks whether a k/v free operation frees an areawhich contains an object which has not been deactivatedproperly. This can make kmalloc/kfree-intensive workloadsmuch slower.config DEBUG_OBJECTS_TIMERSbool "Debug timer objects"depends on DEBUG_OBJECTShelpIf you say Y here, additional code will be inserted into thetimer routines to track the life time of timer objects andvalidate the timer operations.config DEBUG_OBJECTS_WORKbool "Debug work objects"depends on DEBUG_OBJECTShelpIf you say Y here, additional code will be inserted into thework queue routines to track the life time of work objects andvalidate the work operations.config DEBUG_OBJECTS_RCU_HEADbool "Debug RCU callbacks objects"depends on DEBUG_OBJECTShelpEnable this to turn on debugging of RCU list heads (call_rcu() usage).config DEBUG_OBJECTS_PERCPU_COUNTERbool "Debug percpu counter objects"depends on DEBUG_OBJECTShelpIf you say Y here, additional code will be inserted into thepercpu counter routines to track the life time of percpu counterobjects and validate the percpu counter operations.config DEBUG_OBJECTS_ENABLE_DEFAULTint "debug_objects bootup default value (0-1)"range 0 1default "1"depends on DEBUG_OBJECTShelpDebug objects boot parameter default valueconfig DEBUG_SLABbool "Debug slab memory allocations"depends on DEBUG_KERNEL && SLAB && !KMEMCHECKhelpSay Y here to have the kernel do limited verification on memoryallocation as well as poisoning memory on free to catch use of freedmemory. This can make kmalloc/kfree-intensive workloads much slower.config DEBUG_SLAB_LEAKbool "Memory leak debugging"depends on DEBUG_SLABconfig SLUB_DEBUG_ONbool "SLUB debugging on by default"depends on SLUB && SLUB_DEBUG && !KMEMCHECKdefault nhelpBoot with debugging on by default. SLUB boots by default withthe runtime debug capabilities switched off. Enabling this isequivalent to specifying the "slub_debug" parameter on boot.There is no support for more fine grained debug control likepossible with slub_debug=xxx. SLUB debugging may be switchedoff in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying"slub_debug=-".config SLUB_STATSdefault nbool "Enable SLUB performance statistics"depends on SLUB && SYSFShelpSLUB statistics are useful to debug SLUBs allocation behavior inorder find ways to optimize the allocator. This should never beenabled for production use since keeping statistics slows downthe allocator by a few percentage points. The slabinfo commandsupports the determination of the most active slabs to figureout which slabs are relevant to a particular load.Try running: slabinfo -DAconfig HAVE_DEBUG_KMEMLEAKboolconfig DEBUG_KMEMLEAKbool "Kernel memory leak detector"depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAKselect DEBUG_FSselect STACKTRACE if STACKTRACE_SUPPORTselect KALLSYMSselect CRC32helpSay Y here if you want to enable the memory leakdetector. The memory allocation/freeing is traced in a waysimilar to the Boehm's conservative garbage collector, thedifference being that the orphan objects are not freed butonly shown in /sys/kernel/debug/kmemleak. Enabling thisfeature will introduce an overhead to memoryallocations. See Documentation/kmemleak.txt for moredetails.Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chancesof finding leaks due to the slab objects poisoning.In order to access the kmemleak file, debugfs needs to bemounted (usually at /sys/kernel/debug).config DEBUG_KMEMLEAK_EARLY_LOG_SIZEint "Maximum kmemleak early log entries"depends on DEBUG_KMEMLEAKrange 200 40000default 400helpKmemleak must track all the memory allocations to avoidreporting false positives. Since memory may be allocated orfreed before kmemleak is initialised, an early log buffer isused to store these actions. If kmemleak reports "early logbuffer exceeded", please increase this value.config DEBUG_KMEMLEAK_TESTtristate "Simple test for the kernel memory leak detector"depends on DEBUG_KMEMLEAK && mhelpThis option enables a module that explicitly leaks memory.If unsure, say N.config DEBUG_KMEMLEAK_DEFAULT_OFFbool "Default kmemleak to off"depends on DEBUG_KMEMLEAKhelpSay Y here to disable kmemleak by default. It can then be enabledon the command line via kmemleak=on.config DEBUG_STACK_USAGEbool "Stack utilization instrumentation"depends on DEBUG_KERNEL && !IA64 && !PARISC && !METAGhelpEnables the display of the minimum amount of free stack which eachtask has ever had available in the sysrq-T and sysrq-P debug output.This option will slow down process creation somewhat.config DEBUG_VMbool "Debug VM"depends on DEBUG_KERNELhelpEnable this to turn on extended checks in the virtual-memory systemthat may impact performance.If unsure, say N.config DEBUG_VM_VMACACHEbool "Debug VMA caching"depends on DEBUG_VMhelpEnable this to turn on VMA caching debug information. Doing socan cause significant overhead, so only enable it in non-productionenvironments.If unsure, say N.config DEBUG_VM_RBbool "Debug VM red-black trees"depends on DEBUG_VMhelpEnable VM red-black tree debugging information and extra validations.If unsure, say N.config DEBUG_VIRTUALbool "Debug VM translations"depends on DEBUG_KERNEL && X86helpEnable some costly sanity checks in virtual to page code. This cancatch mistakes with virt_to_page() and friends.If unsure, say N.config DEBUG_NOMMU_REGIONSbool "Debug the global anon/private NOMMU mapping region tree"depends on DEBUG_KERNEL && !MMUhelpThis option causes the global tree of anonymous and private mappingregions to be regularly checked for invalid topology.config DEBUG_MEMORY_INITbool "Debug memory initialisation" if EXPERTdefault !EXPERThelpEnable this for additional checks during memory initialisation.The sanity checks verify aspects of the VM such as the memory modeland other information provided by the architecture. Verboseinformation will be printed at KERN_DEBUG loglevel dependingon the mminit_loglevel= command-line option.If unsure, say Yconfig MEMORY_NOTIFIER_ERROR_INJECTtristate "Memory hotplug notifier error injection module"depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTIONhelpThis option provides the ability to inject artificial errors tomemory hotplug notifier chain callbacks. It is controlled throughdebugfs interface under /sys/kernel/debug/notifier-error-inject/memoryIf the notifier call chain should be failed with some eventsnotified, 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/statebash: echo: write error: Cannot allocate memoryTo compile this code as a module, choose M here: the module willbe called memory-notifier-error-inject.If unsure, say N.config DEBUG_PER_CPU_MAPSbool "Debug access to per_cpu maps"depends on DEBUG_KERNELdepends on SMPhelpSay Y to verify that the per_cpu map being accessed hasbeen set up. This adds a fair amount of code to kernel memoryand decreases performance.Say N if unsure.config DEBUG_HIGHMEMbool "Highmem debugging"depends on DEBUG_KERNEL && HIGHMEMhelpThis option enables additional error checking for high memorysystems. Disable for production systems.config HAVE_DEBUG_STACKOVERFLOWboolconfig DEBUG_STACKOVERFLOWbool "Check for stack overflows"depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW---help---Say Y here if you want to check for overflows of kernel, IRQand exception stacks (if your architecture uses them). Thisoption will show detailed messages if free stack space dropsbelow a certain limit.These kinds of bugs usually occur when call-chains in thekernel get too deep, especially when interrupts areinvolved.Use this in cases where you see apparently random memorycorruption, especially if it appears in 'struct thread_info'If in doubt, say "N".source "lib/Kconfig.kmemcheck"source "lib/Kconfig.kasan"endmenu # "Memory Debugging"config DEBUG_SHIRQbool "Debug shared IRQ handlers"depends on DEBUG_KERNELhelpEnable this to generate a spurious interrupt as soon as a sharedinterrupt handler is registered, and just before one is deregistered.Drivers ought to be able to handle interrupts coming in at thosepoints; some don't and need to be caught.menu "Debug Lockups and Hangs"config LOCKUP_DETECTORbool "Detect Hard and Soft Lockups"depends on DEBUG_KERNEL && !S390helpSay Y here to enable the kernel to act as a watchdog to detecthard and soft lockups.Softlockups are bugs that cause the kernel to loop in kernelmode for more than 20 seconds, without giving other tasks achance to run. The current stack trace is displayed upondetection and the system will stay locked up.Hardlockups are bugs that cause the CPU to loop in kernel modefor more than 10 seconds, without letting other interrupts have achance to run. The current stack trace is displayed upon detectionand the system will stay locked up.The overhead should be minimal. A periodic hrtimer runs togenerate 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 lockupthresholds can be controlled through the sysctl watchdog_thresh.config HARDLOCKUP_DETECTORdef_bool ydepends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOGdepends on PERF_EVENTS && HAVE_PERF_EVENTS_NMIconfig BOOTPARAM_HARDLOCKUP_PANICbool "Panic (Reboot) On Hard Lockups"depends on HARDLOCKUP_DETECTORhelpSay Y here to enable the kernel to panic on "hard lockups",which are bugs that cause the kernel to loop in kernelmode with interrupts disabled for more than 10 seconds (configurableusing the watchdog_thresh sysctl).Say N if unsure.config BOOTPARAM_HARDLOCKUP_PANIC_VALUEintdepends on HARDLOCKUP_DETECTORrange 0 1default 0 if !BOOTPARAM_HARDLOCKUP_PANICdefault 1 if BOOTPARAM_HARDLOCKUP_PANICconfig BOOTPARAM_SOFTLOCKUP_PANICbool "Panic (Reboot) On Soft Lockups"depends on LOCKUP_DETECTORhelpSay Y here to enable the kernel to panic on "soft lockups",which are bugs that cause the kernel to loop in kernelmode for more than 20 seconds (configurable using the watchdog_threshsysctl), 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 alockup has been detected. This feature is useful forhigh-availability systems that have uptime guarantees andwhere a lockup must be resolved ASAP.Say N if unsure.config BOOTPARAM_SOFTLOCKUP_PANIC_VALUEintdepends on LOCKUP_DETECTORrange 0 1default 0 if !BOOTPARAM_SOFTLOCKUP_PANICdefault 1 if BOOTPARAM_SOFTLOCKUP_PANICconfig DETECT_HUNG_TASKbool "Detect Hung Tasks"depends on DEBUG_KERNELdefault LOCKUP_DETECTORhelpSay Y here to enable the kernel to detect "hung tasks",which are bugs that cause the task to be stuck inuninterruptible "D" state indefinitiley.When a hung task is detected, the kernel will print thecurrent stack trace (which you should report), but thetask will stay in uninterruptible state. If lockdep isenabled then all held locks will also be reported. Thisfeature has negligible overhead.config DEFAULT_HUNG_TASK_TIMEOUTint "Default timeout for hung task detection (in seconds)"depends on DETECT_HUNG_TASKdefault 120helpThis option controls the default timeout (in seconds) usedto determine when a task has become non-responsive and shouldbe considered hung.It can be adjusted at runtime via the kernel.hung_task_timeout_secssysctl 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_PANICbool "Panic (Reboot) On Hung Tasks"depends on DETECT_HUNG_TASKhelpSay Y here to enable the kernel to panic on "hung tasks",which are bugs that cause the kernel to leave a task stuckin uninterruptible "D" state.The panic can be used in combination with panic_timeout,to cause the system to reboot automatically after ahung task has been detected. This feature is useful forhigh-availability systems that have uptime guarantees andwhere a hung tasks must be resolved ASAP.Say N if unsure.config BOOTPARAM_HUNG_TASK_PANIC_VALUEintdepends on DETECT_HUNG_TASKrange 0 1default 0 if !BOOTPARAM_HUNG_TASK_PANICdefault 1 if BOOTPARAM_HUNG_TASK_PANICendmenu # "Debug lockups and hangs"config PANIC_ON_OOPSbool "Panic on Oops"helpSay Y here to enable the kernel to panic when it oopses. Thishas the same effect as setting oops=panic on the kernel commandline.This feature is useful to ensure that the kernel does not doanything erroneous after an oops which could result in datacorruption or other issues.Say N if unsure.config PANIC_ON_OOPS_VALUEintrange 0 1default 0 if !PANIC_ON_OOPSdefault 1 if PANIC_ON_OOPSconfig PANIC_TIMEOUTint "panic timeout"default 0helpSet the timeout value (in seconds) until a reboot occurs when thethe kernel panics. If n = 0, then we wait forever. A timeoutvalue n > 0 will wait n seconds before rebooting, while a timeoutvalue n < 0 will reboot immediately.config SCHED_DEBUGbool "Collect scheduler debugging info"depends on DEBUG_KERNEL && PROC_FSdefault yhelpIf you say Y here, the /proc/sched_debug file will be providedthat can help debug the scheduler. The runtime overhead of thisoption is minimal.config SCHEDSTATSbool "Collect scheduler statistics"depends on DEBUG_KERNEL && PROC_FShelpIf you say Y here, additional code will be inserted into thescheduler and related routines to collect statistics aboutscheduler behavior and provide them in /proc/schedstat. Thesestats may be useful for both tuning and debugging the schedulerIf you aren't debugging the scheduler or trying to tune a specificapplication, you can say N to avoid the very slight overheadthis adds.config SCHED_STACK_END_CHECKbool "Detect stack corruption on calls to schedule()"depends on DEBUG_KERNELdefault nhelpThis option checks for a stack overrun on calls to schedule().If the stack end location is found to be over written always panic asthe content of the corrupted region can no longer be trusted.This is to ensure no erroneous behaviour occurs which could result indata corruption or a sporadic crash at a later stage once the regionis examined. The runtime overhead introduced is minimal.config TIMER_STATSbool "Collect kernel timers statistics"depends on DEBUG_KERNEL && PROC_FShelpIf you say Y here, additional code will be inserted into thetimer routines to collect statistics about kernel timers beingreprogrammed. 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 informationabout timer usage patterns in kernel and userspace. This featureis lightweight if enabled in the kernel config but not activated(it defaults to deactivated on bootup and will only be activatedif some application like powertop activates it explicitly).config DEBUG_PREEMPTbool "Debug preemptible kernel"depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORTdefault yhelpIf you say Y here then the kernel will use a debug variant of thecommonly used smp_processor_id() function and will print warningsif kernel code uses it in a preemption-unsafe way. Also, the kernelwill detect preemption count underflows.menu "Lock Debugging (spinlocks, mutexes, etc...)"config DEBUG_RT_MUTEXESbool "RT Mutex debugging, deadlock detection"depends on DEBUG_KERNEL && RT_MUTEXEShelpThis allows rt mutex semantics violations and rt mutex relateddeadlocks (lockups) to be detected and reported automatically.config RT_MUTEX_TESTERbool "Built-in scriptable tester for rt-mutexes"depends on DEBUG_KERNEL && RT_MUTEXES && BROKENhelpThis option enables a rt-mutex tester.config DEBUG_SPINLOCKbool "Spinlock and rw-lock debugging: basic checks"depends on DEBUG_KERNELselect UNINLINE_SPIN_UNLOCKhelpSay Y here and build SMP to catch missing spinlock initializationand certain other kinds of spinlock errors commonly made. This isbest used in conjunction with the NMI watchdog so that spinlockdeadlocks are also debuggable.config DEBUG_MUTEXESbool "Mutex debugging: basic checks"depends on DEBUG_KERNELhelpThis feature allows mutex semantics violations to be detected andreported.config DEBUG_WW_MUTEX_SLOWPATHbool "Wait/wound mutex debugging: Slowpath testing"depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORTselect DEBUG_LOCK_ALLOCselect DEBUG_SPINLOCKselect DEBUG_MUTEXEShelpThis feature enables slowpath testing for w/w mutex users byinjecting additional -EDEADLK wound/backoff cases. Together withthe full mutex checks enabled with (CONFIG_PROVE_LOCKING) thiswill test all possible w/w mutex interface abuse with theexception of simply not acquiring all the required locks.Note that this feature can introduce significant overhead, soit really should not be enabled in a production or distro kernel,even a debug kernel. If you are a driver writer, enable it. Ifyou are a distro, do not.config DEBUG_LOCK_ALLOCbool "Lock debugging: detect incorrect freeing of live locks"depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORTselect DEBUG_SPINLOCKselect DEBUG_MUTEXESselect LOCKDEPhelpThis feature will check whether any held lock (spinlock, rwlock,mutex or rwsem) is incorrectly freed by the kernel, via any of thememory-freeing routines (kfree(), kmem_cache_free(), free_pages(),vfree(), etc.), whether a live lock is incorrectly reinitialized viaspin_lock_init()/mutex_init()/etc., or whether there is any lockheld during task exit.config PROVE_LOCKINGbool "Lock debugging: prove locking correctness"depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORTselect LOCKDEPselect DEBUG_SPINLOCKselect DEBUG_MUTEXESselect DEBUG_LOCK_ALLOCselect TRACE_IRQFLAGSdefault nhelpThis feature enables the kernel to prove that all lockingthat occurs in the kernel runtime is mathematicallycorrect: that under no circumstance could an arbitrary (andnot yet triggered) combination of observed lockingsequences (on an arbitrary number of CPUs, running anarbitrary number of tasks and interrupt contexts) cause adeadlock.In short, this feature enables the kernel to report lockingrelated deadlocks before they actually occur.The proof does not depend on how hard and complex adeadlock scenario would be to trigger: how manyparticipant CPUs, tasks and irq-contexts would be neededfor it to trigger. The proof also does not depend ontiming: if a race and a resulting deadlock is possibletheoretically (no matter how unlikely the race scenariois), it will be proven so and will immediately bereported by the kernel (once the event is observed thatmakes the deadlock theoretically possible).If a deadlock is impossible (i.e. the locking rules, asobserved by the kernel, are mathematically correct), thekernel reports nothing.NOTE: this feature can also be enabled for rwlocks, mutexesand rwsems - in which case all dependencies between thesedifferent locking variants are observed and mapped too, andthe proof of observed correctness is also maintained for anarbitrary combination of these separate locking variants.For more details, see Documentation/locking/lockdep-design.txt.config LOCKDEPbooldepends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORTselect STACKTRACEselect FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCOREselect KALLSYMSselect KALLSYMS_ALLconfig LOCK_STATbool "Lock usage statistics"depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORTselect LOCKDEPselect DEBUG_SPINLOCKselect DEBUG_MUTEXESselect DEBUG_LOCK_ALLOCdefault nhelpThis feature enables tracking lock contention pointsFor more details, see Documentation/locking/lockstat.txtThis also enables lock events required by "perf lock",subcommand of perf.If you want to use "perf lock", you also need to turn onCONFIG_EVENT_TRACING.CONFIG_LOCK_STAT defines "contended" and "acquired" lock events.(CONFIG_LOCKDEP defines "acquire" and "release" events.)config DEBUG_LOCKDEPbool "Lock dependency engine debugging"depends on DEBUG_KERNEL && LOCKDEPhelpIf you say Y here, the lock dependency engine will doadditional runtime checks to debug itself, at the priceof more runtime overhead.config DEBUG_ATOMIC_SLEEPbool "Sleep inside atomic section checking"select PREEMPT_COUNTdepends on DEBUG_KERNELhelpIf you say Y here, various routines which may sleep will become verynoisy if they are called inside atomic sections: when a spinlock isheld, inside an rcu read side critical section, inside preempt disabledsections, inside an interrupt, etc...config DEBUG_LOCKING_API_SELFTESTSbool "Locking API boot-time self-tests"depends on DEBUG_KERNELhelpSay Y here if you want the kernel to run a short self-test duringbootup. The self-test checks whether common types of locking bugsare detected by debugging mechanisms or not. (if you disablelock debugging then those bugs wont be detected of course.)The following locking APIs are covered: spinlocks, rwlocks,mutexes and rwsems.config LOCK_TORTURE_TESTtristate "torture tests for locking"depends on DEBUG_KERNELselect TORTURE_TESTdefault nhelpThis option provides a kernel module that runs torture testson kernel locking primitives. The kernel module may be builtafter the fact on the running kernel to be tested, if desired.Say Y here if you want kernel locking-primitive torture teststo be built into the kernel.Say M if you want these torture tests to build as a module.Say N if you are unsure.endmenu # lock debuggingconfig TRACE_IRQFLAGSboolhelpEnables hooks to interrupt enabling and disabling foreither tracing or lock debugging.config STACKTRACEbool "Stack backtrace support"depends on STACKTRACE_SUPPORThelpThis option causes the kernel to create a /proc/pid/stack forevery process, showing its current stack trace.It is also used by various kernel debugging features that requirestack trace generation.config DEBUG_KOBJECTbool "kobject debugging"depends on DEBUG_KERNELhelpIf you say Y here, some extra kobject debugging messages will be sentto the syslog.config DEBUG_KOBJECT_RELEASEbool "kobject release debugging"depends on DEBUG_OBJECTS_TIMERShelpkobjects are reference counted objects. This means that theirlast reference count put is not predictable, and the kobject canlive on past the point at which a driver decides to drop it'sinitial reference to the kobject gained on allocation. Anexample of this would be a struct device which has just beenunregistered.However, some buggy drivers assume that after such an operation,the memory backing the kobject can be immediately freed. Thisgoes completely against the principles of a refcounted object.If you say Y here, the kernel will delay the release of kobjectson the last reference count to improve the visibility of thiskind of kobject release bug.config HAVE_DEBUG_BUGVERBOSEboolconfig DEBUG_BUGVERBOSEbool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERTdepends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE)default yhelpSay Y here to make BUG() panics output the file name and line numberof the BUG call as well as the EIP and oops trace. This aidsdebugging but costs about 70-100K of memory.config DEBUG_LISTbool "Debug linked list manipulation"depends on DEBUG_KERNELhelpEnable this to turn on extended checks in the linked-listwalking routines.If unsure, say N.config DEBUG_PI_LISTbool "Debug priority linked list manipulation"depends on DEBUG_KERNELhelpEnable this to turn on extended checks in the priority-orderedlinked-list (plist) walking routines. This checks the entirelist multiple times during each manipulation.If unsure, say N.config DEBUG_SGbool "Debug SG table operations"depends on DEBUG_KERNELhelpEnable this to turn on checks on scatter-gather tables. This canhelp find problems with drivers that do not properly initializetheir sg tables.If unsure, say N.config DEBUG_NOTIFIERSbool "Debug notifier call chains"depends on DEBUG_KERNELhelpEnable this to turn on sanity checking for notifier call chains.This is most useful for kernel developers to make sure thatmodules properly unregister themselves from notifier chains.This is a relatively cheap check but if you care about maximumperformance, say N.config DEBUG_CREDENTIALSbool "Debug credential management"depends on DEBUG_KERNELhelpEnable this to turn on some debug checking for credentialmanagement. The additional code keeps track of the number ofpointers from task_structs to any given cred struct, and checks tosee that this number never exceeds the usage count of the credstruct.Furthermore, if SELinux is enabled, this also checks that thesecurity pointer in the cred struct is never seen to be invalid.If unsure, say N.menu "RCU Debugging"config PROVE_RCUbool "RCU debugging: prove RCU correctness"depends on PROVE_LOCKINGdefault nhelpThis feature enables lockdep extensions that check for correctuse of RCU APIs. This is currently under development. Say Yif you want to debug RCU usage or help work on the PROVE_RCUfeature.Say N if you are unsure.config PROVE_RCU_REPEATEDLYbool "RCU debugging: don't disable PROVE_RCU on first splat"depends on PROVE_RCUdefault nhelpBy itself, PROVE_RCU will disable checking upon issuing thefirst warning (or "splat"). This feature prevents suchdisabling, allowing multiple RCU-lockdep warnings to be printedon a single reboot.Say Y to allow multiple RCU-lockdep warnings per boot.Say N if you are unsure.config SPARSE_RCU_POINTERbool "RCU debugging: sparse-based checks for pointer usage"default nhelpThis feature enables the __rcu sparse annotation forRCU-protected pointers. This annotation will cause sparseto flag any non-RCU used of annotated pointers. This can behelpful when debugging RCU usage. Please note that this featureis not intended to enforce code cleanliness; it is instead merelya debugging aid.Say Y to make sparse flag questionable use of RCU-protected pointersSay N if you are unsure.config TORTURE_TESTtristatedefault nconfig RCU_TORTURE_TESTtristate "torture tests for RCU"depends on DEBUG_KERNELselect TORTURE_TESTselect SRCUdefault nhelpThis option provides a kernel module that runs torture testson the RCU infrastructure. The kernel module may be builtafter the fact on the running kernel to be tested, if desired.Say Y here if you want RCU torture tests to be built intothe 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_RUNNABLEbool "torture tests for RCU runnable by default"depends on RCU_TORTURE_TEST = ydefault nhelpThis option provides a way to build the RCU torture testsdirectly into the kernel without them starting up at boottime. You can use /proc/sys/kernel/rcutorture_runnableto manually override this setting. This /proc file isavailable only when the RCU torture tests have been builtinto the kernel.Say Y here if you want the RCU torture tests to start duringboot (you probably don't).Say N here if you want the RCU torture tests to start onlyafter being manually enabled via /proc.config RCU_CPU_STALL_TIMEOUTint "RCU CPU stall timeout in seconds"depends on RCU_STALL_COMMONrange 3 300default 21helpIf a given RCU grace period extends more than the specifiednumber of seconds, a CPU stall warning is printed. If theRCU grace period persists, additional CPU stall warnings areprinted at more widely spaced intervals.config RCU_CPU_STALL_INFObool "Print additional diagnostics on RCU CPU stall"depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNELdefault yhelpFor each stalled CPU that is aware of the current RCU graceperiod, print out additional per-CPU diagnostic informationregarding 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_TRACEbool "Enable tracing for RCU"depends on DEBUG_KERNELselect TRACE_CLOCKhelpThis option provides tracing in RCU which presents statsin debugfs for debugging RCU implementation.Say Y here if you want to enable RCU tracingSay N if you are unsure.endmenu # "RCU Debugging"config DEBUG_BLOCK_EXT_DEVTbool "Force extended block device numbers and spread them"depends on DEBUG_KERNELdepends on BLOCKdefault nhelpBIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ONSOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHATYOU ARE DOING. Distros, please enable this and fix whateveris broken.Conventionally, block device numbers are allocated frompredetermined contiguous area. However, extended block areamay introduce non-contiguous block device numbers. Thisoption forces most block device numbers to be allocated fromthe extended space and spreads them to discover kernel oruserland code paths which assume predetermined contiguousdevice number allocation.Note that turning on this debug option shuffles all thedevice numbers for all IDE and SCSI devices including libataones, so root partition specified using device numberdirectly (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 NOTIFIER_ERROR_INJECTIONtristate "Notifier error injection"depends on DEBUG_KERNELselect DEBUG_FShelpThis option provides the ability to inject artificial errors tospecified notifier chain callbacks. It is useful to test the errorhandling of notifier call chain failures.Say N if unsure.config CPU_NOTIFIER_ERROR_INJECTtristate "CPU notifier error injection module"depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTIONhelpThis option provides a kernel module that can be used to testthe error handling of the cpu notifiers by injecting artificialerrors to CPU notifier chain callbacks. It is controlled throughdebugfs interface under /sys/kernel/debug/notifier-error-inject/cpuIf the notifier call chain should be failed with some eventsnotified, 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/onlinebash: echo: write error: Operation not permittedTo compile this code as a module, choose M here: the module willbe called cpu-notifier-error-inject.If unsure, say N.config PM_NOTIFIER_ERROR_INJECTtristate "PM notifier error injection module"depends on PM && NOTIFIER_ERROR_INJECTIONdefault m if PM_DEBUGhelpThis option provides the ability to inject artificial errors toPM notifier chain callbacks. It is controlled through debugfsinterface /sys/kernel/debug/notifier-error-inject/pmIf the notifier call chain should be failed with some eventsnotified, 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/statebash: echo: write error: Cannot allocate memoryTo compile this code as a module, choose M here: the module willbe called pm-notifier-error-inject.If unsure, say N.config OF_RECONFIG_NOTIFIER_ERROR_INJECTtristate "OF reconfig notifier error injection module"depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTIONhelpThis option provides the ability to inject artificial errors toOF reconfig notifier chain callbacks. It is controlledthrough debugfs interface under/sys/kernel/debug/notifier-error-inject/OF-reconfig/If the notifier call chain should be failed with some eventsnotified, write the error code to "actions/<notifier event>/error".To compile this code as a module, choose M here: the module willbe called of-reconfig-notifier-error-inject.If unsure, say N.config FAULT_INJECTIONbool "Fault-injection framework"depends on DEBUG_KERNELhelpProvide fault-injection framework.For more details, see Documentation/fault-injection/.config FAILSLABbool "Fault-injection capability for kmalloc"depends on FAULT_INJECTIONdepends on SLAB || SLUBhelpProvide fault-injection capability for kmalloc.config FAIL_PAGE_ALLOCbool "Fault-injection capabilitiy for alloc_pages()"depends on FAULT_INJECTIONhelpProvide fault-injection capability for alloc_pages().config FAIL_MAKE_REQUESTbool "Fault-injection capability for disk IO"depends on FAULT_INJECTION && BLOCKhelpProvide fault-injection capability for disk IO.config FAIL_IO_TIMEOUTbool "Fault-injection capability for faking disk interrupts"depends on FAULT_INJECTION && BLOCKhelpProvide fault-injection capability on end IO handling. Thiswill 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_REQUESTbool "Fault-injection capability for MMC IO"select DEBUG_FSdepends on FAULT_INJECTION && MMChelpProvide fault-injection capability for MMC IO.This will make the mmc core return data errors. This isuseful to test the error handling in the mmc block deviceand to test how the mmc host driver handles retries fromthe block device.config FAULT_INJECTION_DEBUG_FSbool "Debugfs entries for fault-injection capabilities"depends on FAULT_INJECTION && SYSFS && DEBUG_FShelpEnable configuration of fault-injection capabilities via debugfs.config FAULT_INJECTION_STACKTRACE_FILTERbool "stacktrace filter for fault-injection capabilities"depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORTdepends on !X86_64select STACKTRACEselect FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCOREhelpProvide stacktrace filter for fault-injection capabilitiesconfig LATENCYTOPbool "Latency measuring infrastructure"depends on HAVE_LATENCYTOP_SUPPORTdepends on DEBUG_KERNELdepends on STACKTRACE_SUPPORTdepends on PROC_FSselect FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARCselect KALLSYMSselect KALLSYMS_ALLselect STACKTRACEselect SCHEDSTATSselect SCHED_DEBUGhelpEnable this option if you want to use the LatencyTOP toolto find out which userspace is blocking on what kernel operations.config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKSboolconfig DEBUG_STRICT_USER_COPY_CHECKSbool "Strict user copy size checks"depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKSdepends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILINGhelpEnabling this option turns a certain set of sanity checks for usercopy operations into compile time failures.The copy_from_user() etc checks are there to help test if thereare sufficient security checks on the length argument ofthe copy operation, by having gcc prove that the argument iswithin bounds.If unsure, say N.source kernel/trace/Kconfigmenu "Runtime Testing"config LKDTMtristate "Linux Kernel Dump Test Tool Module"depends on DEBUG_FSdepends on BLOCKdefault nhelpThis module enables testing of the different dumping mechanisms byinducing system failures at predefined crash points.If you don't need it: say NChoose M here to compile this code as a module. The module will becalled lkdtm.Documentation on how to use the module can be found inDocumentation/fault-injection/provoke-crashes.txtconfig TEST_LIST_SORTbool "Linked list sorting test"depends on DEBUG_KERNELhelpEnable this to turn on 'list_sort()' function test. This test isexecuted only once during system boot, so affects only boot time.If unsure, say N.config KPROBES_SANITY_TESTbool "Kprobes sanity tests"depends on DEBUG_KERNELdepends on KPROBESdefault nhelpThis option provides for testing basic kprobes functionality onboot. A sample kprobe, jprobe and kretprobe are inserted andverified for functionality.Say N if you are unsure.config BACKTRACE_SELF_TESTtristate "Self test for the backtrace code"depends on DEBUG_KERNELdefault nhelpThis option provides a kernel module that can be used to testthe kernel stack backtrace code. This option is not usefulfor distributions or general kernels, but only for kerneldevelopers working on architecture code.Note that if you want to also test saved backtraces, you willhave to enable STACKTRACE as well.Say N if you are unsure.config RBTREE_TESTtristate "Red-Black tree test"depends on DEBUG_KERNELhelpA benchmark measuring the performance of the rbtree library.Also includes rbtree invariant checks.config INTERVAL_TREE_TESTtristate "Interval tree test"depends on m && DEBUG_KERNELselect INTERVAL_TREEhelpA benchmark measuring the performance of the interval tree libraryconfig PERCPU_TESTtristate "Per cpu operations test"depends on m && DEBUG_KERNELhelpEnable this option to build test module which validates per-cpuoperations.If unsure, say N.config ATOMIC64_SELFTESTbool "Perform an atomic64_t self-test at boot"helpEnable this option to test the atomic64_t functions at boot.If unsure, say N.config ASYNC_RAID6_TESTtristate "Self test for hardware accelerated raid6 recovery"depends on ASYNC_RAID6_RECOVselect ASYNC_MEMCPY---help---This is a one-shot self test that permutes through therecovery of all the possible two disk failure scenarios for aN-disk array. Recovery is performed with the asynchronousraid6 recovery routines, and will optionally use an offloadengine if one is available.If unsure, say N.config TEST_HEXDUMPtristate "Test functions located in the hexdump module at runtime"config TEST_STRING_HELPERStristate "Test functions located in the string_helpers module at runtime"config TEST_KSTRTOXtristate "Test kstrto*() family of functions at runtime"config TEST_RHASHTABLEtristate "Perform selftest on resizable hash table"default nhelpEnable this option to test the rhashtable functions at boot.If unsure, say N.endmenu # runtime testsconfig PROVIDE_OHCI1394_DMA_INITbool "Remote debugging over FireWire early on boot"depends on PCI && X86helpIf you want to debug problems which hang or crash the kernel earlyon boot and the crashing machine has a FireWire port, you can usethis feature to remotely access the memory of the crashed machineover FireWire. This employs remote DMA as part of the OHCI1394specification which is now the standard for FireWire controllers.With remote DMA, you can monitor the printk buffer remotely usingfirescope 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 initializeall OHCI1394 controllers which are found in the PCI config space.As all changes to the FireWire bus such as enabling and disablingdevices cause a bus reset and thereby disable remote DMA for alldevices, be sure to have the cable plugged and FireWire enabled onthe debugging host before booting the debug target for debugging.This code (~1k) is freed after boot. By then, the firewire stackin charge of the OHCI-1394 controllers should be used instead.See Documentation/debugging-via-ohci1394.txt for more information.config BUILD_DOCSRCbool "Build targets in Documentation/ tree"depends on HEADERS_CHECKhelpThis option attempts to build objects from the source files in thekernel Documentation/ tree.Say N if you are unsure.config DMA_API_DEBUGbool "Enable debugging of DMA-API usage"depends on HAVE_DMA_API_DEBUGhelpEnable 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 devicedrivers like double-freeing of DMA mappings or freeing mappings thatwere never allocated.This also attempts to catch cases where a page owned by DMA isaccessed by the cpu in a way that could cause data corruption. Forexample, this enables cow_user_page() to check that the source page isnot undergoing DMA.This option causes a performance degradation. Use only if you want todebug device drivers and dma interactions.If unsure, say N.config TEST_LKMtristate "Test module loading with 'hello world' module"default ndepends on mhelpThis builds the "test_module" module that emits "Hello, world"on printk when loaded. It is designed to be used for basicevaluation of the module loading subsystem (for example whenvalidating module verification). It lacks any extra dependencies,and will not normally be loaded by the system unless explicitlyrequested by name.If unsure, say N.config TEST_USER_COPYtristate "Test user/kernel boundary protections"default ndepends on mhelpThis builds the "test_user_copy" module that runs sanity checkson the copy_to/from_user infrastructure, making sure basicuser/kernel boundary testing is working. If it fails to load,a regression has been detected in the user/kernel memory boundaryprotections.If unsure, say N.config TEST_BPFtristate "Test BPF filter functionality"default ndepends on m && NEThelpThis builds the "test_bpf" module that runs various test vectorsagainst the BPF interpreter or BPF JIT compiler depending on thecurrent setting. This is in particular useful for BPF JIT compilerdevelopment, but also to run regression tests against changes inthe interpreter code. It also enables test stubs for eBPF maps andverifier used by user space verifier testsuite.If unsure, say N.config TEST_FIRMWAREtristate "Test firmware loading via userspace interface"default ndepends on FW_LOADERhelpThis builds the "test_firmware" module that creates a userspaceinterface for testing firmware loading. This can be used tocontrol the triggering of firmware loading without needing anactual firmware-using device. The contents can be rechecked byuserspace.If unsure, say N.config TEST_UDELAYtristate "udelay test driver"default nhelpThis builds the "udelay_test" module that helps to make surethat udelay() is working properly.If unsure, say N.source "samples/Kconfig"source "lib/Kconfig.kgdb"
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