1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 depends on PRINTK 5 help 6 Selecting this option causes timing information to be 7 included in printk output. This allows you to measure 8 the interval between kernel operations, including bootup 9 operations. This is useful for identifying long delays 10 in kernel startup. Or add printk.time=1 at boot-time. 11 See Documentation/kernel-parameters.txt 12 13config DEFAULT_MESSAGE_LOGLEVEL 14 int "Default message log level (1-7)" 15 range 1 7 16 default "4" 17 help 18 Default log level for printk statements with no specified priority. 19 20 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 21 that are auditing their logs closely may want to set it to a lower 22 priority. 23 24config ENABLE_WARN_DEPRECATED 25 bool "Enable __deprecated logic" 26 default y 27 help 28 Enable the __deprecated logic in the kernel build. 29 Disable this to suppress the "warning: 'foo' is deprecated 30 (declared at kernel/power/somefile.c:1234)" messages. 31 32config ENABLE_MUST_CHECK 33 bool "Enable __must_check logic" 34 default y 35 help 36 Enable the __must_check logic in the kernel build. Disable this to 37 suppress the "warning: ignoring return value of 'foo', declared with 38 attribute warn_unused_result" messages. 39 40config FRAME_WARN 41 int "Warn for stack frames larger than (needs gcc 4.4)" 42 range 0 8192 43 default 1024 if !64BIT 44 default 2048 if 64BIT 45 help 46 Tell gcc to warn at build time for stack frames larger than this. 47 Setting this too low will cause a lot of warnings. 48 Setting it to 0 disables the warning. 49 Requires gcc 4.4 50 51config MAGIC_SYSRQ 52 bool "Magic SysRq key" 53 depends on !UML 54 help 55 If you say Y here, you will have some control over the system even 56 if the system crashes for example during kernel debugging (e.g., you 57 will be able to flush the buffer cache to disk, reboot the system 58 immediately or dump some status information). This is accomplished 59 by pressing various keys while holding SysRq (Alt+PrintScreen). It 60 also works on a serial console (on PC hardware at least), if you 61 send a BREAK and then within 5 seconds a command keypress. The 62 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 63 unless you really know what this hack does. 64 65config STRIP_ASM_SYMS 66 bool "Strip assembler-generated symbols during link" 67 default n 68 help 69 Strip internal assembler-generated symbols during a link (symbols 70 that look like '.Lxxx') so they don't pollute the output of 71 get_wchan() and suchlike. 72 73config UNUSED_SYMBOLS 74 bool "Enable unused/obsolete exported symbols" 75 default y if X86 76 help 77 Unused but exported symbols make the kernel needlessly bigger. For 78 that reason most of these unused exports will soon be removed. This 79 option is provided temporarily to provide a transition period in case 80 some external kernel module needs one of these symbols anyway. If you 81 encounter such a case in your module, consider if you are actually 82 using the right API. (rationale: since nobody in the kernel is using 83 this in a module, there is a pretty good chance it's actually the 84 wrong interface to use). If you really need the symbol, please send a 85 mail to the linux kernel mailing list mentioning the symbol and why 86 you really need it, and what the merge plan to the mainline kernel for 87 your module is. 88 89config DEBUG_FS 90 bool "Debug Filesystem" 91 help 92 debugfs is a virtual file system that kernel developers use to put 93 debugging files into. Enable this option to be able to read and 94 write to these files. 95 96 For detailed documentation on the debugfs API, see 97 Documentation/DocBook/filesystems. 98 99 If unsure, say N. 100 101config HEADERS_CHECK 102 bool "Run 'make headers_check' when building vmlinux" 103 depends on !UML 104 help 105 This option will extract the user-visible kernel headers whenever 106 building the kernel, and will run basic sanity checks on them to 107 ensure that exported files do not attempt to include files which 108 were not exported, etc. 109 110 If you're making modifications to header files which are 111 relevant for userspace, say 'Y', and check the headers 112 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 113 your build tree), to make sure they're suitable. 114 115config DEBUG_SECTION_MISMATCH 116 bool "Enable full Section mismatch analysis" 117 help 118 The section mismatch analysis checks if there are illegal 119 references from one section to another section. 120 During linktime or runtime, some sections are dropped; 121 any use of code/data previously in these sections would 122 most likely result in an oops. 123 In the code, functions and variables are annotated with 124 __init, __devinit, etc. (see the full list in include/linux/init.h), 125 which results in the code/data being placed in specific sections. 126 The section mismatch analysis is always performed after a full 127 kernel build, and enabling this option causes the following 128 additional steps to occur: 129 - Add the option -fno-inline-functions-called-once to gcc commands. 130 When inlining a function annotated with __init in a non-init 131 function, we would lose the section information and thus 132 the analysis would not catch the illegal reference. 133 This option tells gcc to inline less (but it does result in 134 a larger kernel). 135 - Run the section mismatch analysis for each module/built-in.o file. 136 When we run the section mismatch analysis on vmlinux.o, we 137 lose valueble information about where the mismatch was 138 introduced. 139 Running the analysis for each module/built-in.o file 140 tells where the mismatch happens much closer to the 141 source. The drawback is that the same mismatch is 142 reported at least twice. 143 - Enable verbose reporting from modpost in order to help resolve 144 the section mismatches that are reported. 145 146config DEBUG_KERNEL 147 bool "Kernel debugging" 148 help 149 Say Y here if you are developing drivers or trying to debug and 150 identify kernel problems. 151 152config DEBUG_SHIRQ 153 bool "Debug shared IRQ handlers" 154 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 155 help 156 Enable this to generate a spurious interrupt as soon as a shared 157 interrupt handler is registered, and just before one is deregistered. 158 Drivers ought to be able to handle interrupts coming in at those 159 points; some don't and need to be caught. 160 161config LOCKUP_DETECTOR 162 bool "Detect Hard and Soft Lockups" 163 depends on DEBUG_KERNEL && !S390 164 help 165 Say Y here to enable the kernel to act as a watchdog to detect 166 hard and soft lockups. 167 168 Softlockups are bugs that cause the kernel to loop in kernel 169 mode for more than 20 seconds, without giving other tasks a 170 chance to run. The current stack trace is displayed upon 171 detection and the system will stay locked up. 172 173 Hardlockups are bugs that cause the CPU to loop in kernel mode 174 for more than 10 seconds, without letting other interrupts have a 175 chance to run. The current stack trace is displayed upon detection 176 and the system will stay locked up. 177 178 The overhead should be minimal. A periodic hrtimer runs to 179 generate interrupts and kick the watchdog task every 4 seconds. 180 An NMI is generated every 10 seconds or so to check for hardlockups. 181 182 The frequency of hrtimer and NMI events and the soft and hard lockup 183 thresholds can be controlled through the sysctl watchdog_thresh. 184 185config HARDLOCKUP_DETECTOR 186 def_bool LOCKUP_DETECTOR && PERF_EVENTS && HAVE_PERF_EVENTS_NMI && \ 187 !HAVE_NMI_WATCHDOG 188 189config BOOTPARAM_HARDLOCKUP_PANIC 190 bool "Panic (Reboot) On Hard Lockups" 191 depends on LOCKUP_DETECTOR 192 help 193 Say Y here to enable the kernel to panic on "hard lockups", 194 which are bugs that cause the kernel to loop in kernel 195 mode with interrupts disabled for more than 10 seconds (configurable 196 using the watchdog_thresh sysctl). 197 198 Say N if unsure. 199 200config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 201 int 202 depends on LOCKUP_DETECTOR 203 range 0 1 204 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 205 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 206 207config BOOTPARAM_SOFTLOCKUP_PANIC 208 bool "Panic (Reboot) On Soft Lockups" 209 depends on LOCKUP_DETECTOR 210 help 211 Say Y here to enable the kernel to panic on "soft lockups", 212 which are bugs that cause the kernel to loop in kernel 213 mode for more than 20 seconds (configurable using the watchdog_thresh 214 sysctl), without giving other tasks a chance to run. 215 216 The panic can be used in combination with panic_timeout, 217 to cause the system to reboot automatically after a 218 lockup has been detected. This feature is useful for 219 high-availability systems that have uptime guarantees and 220 where a lockup must be resolved ASAP. 221 222 Say N if unsure. 223 224config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 225 int 226 depends on LOCKUP_DETECTOR 227 range 0 1 228 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 229 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 230 231config DETECT_HUNG_TASK 232 bool "Detect Hung Tasks" 233 depends on DEBUG_KERNEL 234 default LOCKUP_DETECTOR 235 help 236 Say Y here to enable the kernel to detect "hung tasks", 237 which are bugs that cause the task to be stuck in 238 uninterruptible "D" state indefinitiley. 239 240 When a hung task is detected, the kernel will print the 241 current stack trace (which you should report), but the 242 task will stay in uninterruptible state. If lockdep is 243 enabled then all held locks will also be reported. This 244 feature has negligible overhead. 245 246config DEFAULT_HUNG_TASK_TIMEOUT 247 int "Default timeout for hung task detection (in seconds)" 248 depends on DETECT_HUNG_TASK 249 default 120 250 help 251 This option controls the default timeout (in seconds) used 252 to determine when a task has become non-responsive and should 253 be considered hung. 254 255 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 256 sysctl or by writing a value to 257 /proc/sys/kernel/hung_task_timeout_secs. 258 259 A timeout of 0 disables the check. The default is two minutes. 260 Keeping the default should be fine in most cases. 261 262config BOOTPARAM_HUNG_TASK_PANIC 263 bool "Panic (Reboot) On Hung Tasks" 264 depends on DETECT_HUNG_TASK 265 help 266 Say Y here to enable the kernel to panic on "hung tasks", 267 which are bugs that cause the kernel to leave a task stuck 268 in uninterruptible "D" state. 269 270 The panic can be used in combination with panic_timeout, 271 to cause the system to reboot automatically after a 272 hung task has been detected. This feature is useful for 273 high-availability systems that have uptime guarantees and 274 where a hung tasks must be resolved ASAP. 275 276 Say N if unsure. 277 278config BOOTPARAM_HUNG_TASK_PANIC_VALUE 279 int 280 depends on DETECT_HUNG_TASK 281 range 0 1 282 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 283 default 1 if BOOTPARAM_HUNG_TASK_PANIC 284 285config SCHED_DEBUG 286 bool "Collect scheduler debugging info" 287 depends on DEBUG_KERNEL && PROC_FS 288 default y 289 help 290 If you say Y here, the /proc/sched_debug file will be provided 291 that can help debug the scheduler. The runtime overhead of this 292 option is minimal. 293 294config SCHEDSTATS 295 bool "Collect scheduler statistics" 296 depends on DEBUG_KERNEL && PROC_FS 297 help 298 If you say Y here, additional code will be inserted into the 299 scheduler and related routines to collect statistics about 300 scheduler behavior and provide them in /proc/schedstat. These 301 stats may be useful for both tuning and debugging the scheduler 302 If you aren't debugging the scheduler or trying to tune a specific 303 application, you can say N to avoid the very slight overhead 304 this adds. 305 306config TIMER_STATS 307 bool "Collect kernel timers statistics" 308 depends on DEBUG_KERNEL && PROC_FS 309 help 310 If you say Y here, additional code will be inserted into the 311 timer routines to collect statistics about kernel timers being 312 reprogrammed. The statistics can be read from /proc/timer_stats. 313 The statistics collection is started by writing 1 to /proc/timer_stats, 314 writing 0 stops it. This feature is useful to collect information 315 about timer usage patterns in kernel and userspace. This feature 316 is lightweight if enabled in the kernel config but not activated 317 (it defaults to deactivated on bootup and will only be activated 318 if some application like powertop activates it explicitly). 319 320config DEBUG_OBJECTS 321 bool "Debug object operations" 322 depends on DEBUG_KERNEL 323 help 324 If you say Y here, additional code will be inserted into the 325 kernel to track the life time of various objects and validate 326 the operations on those objects. 327 328config DEBUG_OBJECTS_SELFTEST 329 bool "Debug objects selftest" 330 depends on DEBUG_OBJECTS 331 help 332 This enables the selftest of the object debug code. 333 334config DEBUG_OBJECTS_FREE 335 bool "Debug objects in freed memory" 336 depends on DEBUG_OBJECTS 337 help 338 This enables checks whether a k/v free operation frees an area 339 which contains an object which has not been deactivated 340 properly. This can make kmalloc/kfree-intensive workloads 341 much slower. 342 343config DEBUG_OBJECTS_TIMERS 344 bool "Debug timer objects" 345 depends on DEBUG_OBJECTS 346 help 347 If you say Y here, additional code will be inserted into the 348 timer routines to track the life time of timer objects and 349 validate the timer operations. 350 351config DEBUG_OBJECTS_WORK 352 bool "Debug work objects" 353 depends on DEBUG_OBJECTS 354 help 355 If you say Y here, additional code will be inserted into the 356 work queue routines to track the life time of work objects and 357 validate the work operations. 358 359config DEBUG_OBJECTS_RCU_HEAD 360 bool "Debug RCU callbacks objects" 361 depends on DEBUG_OBJECTS 362 help 363 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 364 365config DEBUG_OBJECTS_PERCPU_COUNTER 366 bool "Debug percpu counter objects" 367 depends on DEBUG_OBJECTS 368 help 369 If you say Y here, additional code will be inserted into the 370 percpu counter routines to track the life time of percpu counter 371 objects and validate the percpu counter operations. 372 373config DEBUG_OBJECTS_ENABLE_DEFAULT 374 int "debug_objects bootup default value (0-1)" 375 range 0 1 376 default "1" 377 depends on DEBUG_OBJECTS 378 help 379 Debug objects boot parameter default value 380 381config DEBUG_SLAB 382 bool "Debug slab memory allocations" 383 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 384 help 385 Say Y here to have the kernel do limited verification on memory 386 allocation as well as poisoning memory on free to catch use of freed 387 memory. This can make kmalloc/kfree-intensive workloads much slower. 388 389config DEBUG_SLAB_LEAK 390 bool "Memory leak debugging" 391 depends on DEBUG_SLAB 392 393config SLUB_DEBUG_ON 394 bool "SLUB debugging on by default" 395 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 396 default n 397 help 398 Boot with debugging on by default. SLUB boots by default with 399 the runtime debug capabilities switched off. Enabling this is 400 equivalent to specifying the "slub_debug" parameter on boot. 401 There is no support for more fine grained debug control like 402 possible with slub_debug=xxx. SLUB debugging may be switched 403 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 404 "slub_debug=-". 405 406config SLUB_STATS 407 default n 408 bool "Enable SLUB performance statistics" 409 depends on SLUB && SYSFS 410 help 411 SLUB statistics are useful to debug SLUBs allocation behavior in 412 order find ways to optimize the allocator. This should never be 413 enabled for production use since keeping statistics slows down 414 the allocator by a few percentage points. The slabinfo command 415 supports the determination of the most active slabs to figure 416 out which slabs are relevant to a particular load. 417 Try running: slabinfo -DA 418 419config DEBUG_KMEMLEAK 420 bool "Kernel memory leak detector" 421 depends on DEBUG_KERNEL && EXPERIMENTAL && \ 422 (X86 || ARM || PPC || MIPS || S390 || SPARC64 || SUPERH || MICROBLAZE || TILE) 423 424 select DEBUG_FS 425 select STACKTRACE if STACKTRACE_SUPPORT 426 select KALLSYMS 427 select CRC32 428 help 429 Say Y here if you want to enable the memory leak 430 detector. The memory allocation/freeing is traced in a way 431 similar to the Boehm's conservative garbage collector, the 432 difference being that the orphan objects are not freed but 433 only shown in /sys/kernel/debug/kmemleak. Enabling this 434 feature will introduce an overhead to memory 435 allocations. See Documentation/kmemleak.txt for more 436 details. 437 438 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 439 of finding leaks due to the slab objects poisoning. 440 441 In order to access the kmemleak file, debugfs needs to be 442 mounted (usually at /sys/kernel/debug). 443 444config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 445 int "Maximum kmemleak early log entries" 446 depends on DEBUG_KMEMLEAK 447 range 200 40000 448 default 400 449 help 450 Kmemleak must track all the memory allocations to avoid 451 reporting false positives. Since memory may be allocated or 452 freed before kmemleak is initialised, an early log buffer is 453 used to store these actions. If kmemleak reports "early log 454 buffer exceeded", please increase this value. 455 456config DEBUG_KMEMLEAK_TEST 457 tristate "Simple test for the kernel memory leak detector" 458 depends on DEBUG_KMEMLEAK && m 459 help 460 This option enables a module that explicitly leaks memory. 461 462 If unsure, say N. 463 464config DEBUG_KMEMLEAK_DEFAULT_OFF 465 bool "Default kmemleak to off" 466 depends on DEBUG_KMEMLEAK 467 help 468 Say Y here to disable kmemleak by default. It can then be enabled 469 on the command line via kmemleak=on. 470 471config DEBUG_PREEMPT 472 bool "Debug preemptible kernel" 473 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 474 default y 475 help 476 If you say Y here then the kernel will use a debug variant of the 477 commonly used smp_processor_id() function and will print warnings 478 if kernel code uses it in a preemption-unsafe way. Also, the kernel 479 will detect preemption count underflows. 480 481config DEBUG_RT_MUTEXES 482 bool "RT Mutex debugging, deadlock detection" 483 depends on DEBUG_KERNEL && RT_MUTEXES 484 help 485 This allows rt mutex semantics violations and rt mutex related 486 deadlocks (lockups) to be detected and reported automatically. 487 488config DEBUG_PI_LIST 489 bool 490 default y 491 depends on DEBUG_RT_MUTEXES 492 493config RT_MUTEX_TESTER 494 bool "Built-in scriptable tester for rt-mutexes" 495 depends on DEBUG_KERNEL && RT_MUTEXES 496 help 497 This option enables a rt-mutex tester. 498 499config DEBUG_SPINLOCK 500 bool "Spinlock and rw-lock debugging: basic checks" 501 depends on DEBUG_KERNEL 502 help 503 Say Y here and build SMP to catch missing spinlock initialization 504 and certain other kinds of spinlock errors commonly made. This is 505 best used in conjunction with the NMI watchdog so that spinlock 506 deadlocks are also debuggable. 507 508config DEBUG_MUTEXES 509 bool "Mutex debugging: basic checks" 510 depends on DEBUG_KERNEL 511 help 512 This feature allows mutex semantics violations to be detected and 513 reported. 514 515config DEBUG_LOCK_ALLOC 516 bool "Lock debugging: detect incorrect freeing of live locks" 517 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 518 select DEBUG_SPINLOCK 519 select DEBUG_MUTEXES 520 select LOCKDEP 521 help 522 This feature will check whether any held lock (spinlock, rwlock, 523 mutex or rwsem) is incorrectly freed by the kernel, via any of the 524 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 525 vfree(), etc.), whether a live lock is incorrectly reinitialized via 526 spin_lock_init()/mutex_init()/etc., or whether there is any lock 527 held during task exit. 528 529config PROVE_LOCKING 530 bool "Lock debugging: prove locking correctness" 531 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 532 select LOCKDEP 533 select DEBUG_SPINLOCK 534 select DEBUG_MUTEXES 535 select DEBUG_LOCK_ALLOC 536 select TRACE_IRQFLAGS 537 default n 538 help 539 This feature enables the kernel to prove that all locking 540 that occurs in the kernel runtime is mathematically 541 correct: that under no circumstance could an arbitrary (and 542 not yet triggered) combination of observed locking 543 sequences (on an arbitrary number of CPUs, running an 544 arbitrary number of tasks and interrupt contexts) cause a 545 deadlock. 546 547 In short, this feature enables the kernel to report locking 548 related deadlocks before they actually occur. 549 550 The proof does not depend on how hard and complex a 551 deadlock scenario would be to trigger: how many 552 participant CPUs, tasks and irq-contexts would be needed 553 for it to trigger. The proof also does not depend on 554 timing: if a race and a resulting deadlock is possible 555 theoretically (no matter how unlikely the race scenario 556 is), it will be proven so and will immediately be 557 reported by the kernel (once the event is observed that 558 makes the deadlock theoretically possible). 559 560 If a deadlock is impossible (i.e. the locking rules, as 561 observed by the kernel, are mathematically correct), the 562 kernel reports nothing. 563 564 NOTE: this feature can also be enabled for rwlocks, mutexes 565 and rwsems - in which case all dependencies between these 566 different locking variants are observed and mapped too, and 567 the proof of observed correctness is also maintained for an 568 arbitrary combination of these separate locking variants. 569 570 For more details, see Documentation/lockdep-design.txt. 571 572config PROVE_RCU 573 bool "RCU debugging: prove RCU correctness" 574 depends on PROVE_LOCKING 575 default n 576 help 577 This feature enables lockdep extensions that check for correct 578 use of RCU APIs. This is currently under development. Say Y 579 if you want to debug RCU usage or help work on the PROVE_RCU 580 feature. 581 582 Say N if you are unsure. 583 584config PROVE_RCU_REPEATEDLY 585 bool "RCU debugging: don't disable PROVE_RCU on first splat" 586 depends on PROVE_RCU 587 default n 588 help 589 By itself, PROVE_RCU will disable checking upon issuing the 590 first warning (or "splat"). This feature prevents such 591 disabling, allowing multiple RCU-lockdep warnings to be printed 592 on a single reboot. 593 594 Say Y to allow multiple RCU-lockdep warnings per boot. 595 596 Say N if you are unsure. 597 598config SPARSE_RCU_POINTER 599 bool "RCU debugging: sparse-based checks for pointer usage" 600 default n 601 help 602 This feature enables the __rcu sparse annotation for 603 RCU-protected pointers. This annotation will cause sparse 604 to flag any non-RCU used of annotated pointers. This can be 605 helpful when debugging RCU usage. Please note that this feature 606 is not intended to enforce code cleanliness; it is instead merely 607 a debugging aid. 608 609 Say Y to make sparse flag questionable use of RCU-protected pointers 610 611 Say N if you are unsure. 612 613config LOCKDEP 614 bool 615 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 616 select STACKTRACE 617 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 618 select KALLSYMS 619 select KALLSYMS_ALL 620 621config LOCK_STAT 622 bool "Lock usage statistics" 623 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 624 select LOCKDEP 625 select DEBUG_SPINLOCK 626 select DEBUG_MUTEXES 627 select DEBUG_LOCK_ALLOC 628 default n 629 help 630 This feature enables tracking lock contention points 631 632 For more details, see Documentation/lockstat.txt 633 634 This also enables lock events required by "perf lock", 635 subcommand of perf. 636 If you want to use "perf lock", you also need to turn on 637 CONFIG_EVENT_TRACING. 638 639 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 640 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 641 642config DEBUG_LOCKDEP 643 bool "Lock dependency engine debugging" 644 depends on DEBUG_KERNEL && LOCKDEP 645 help 646 If you say Y here, the lock dependency engine will do 647 additional runtime checks to debug itself, at the price 648 of more runtime overhead. 649 650config TRACE_IRQFLAGS 651 bool 652 help 653 Enables hooks to interrupt enabling and disabling for 654 either tracing or lock debugging. 655 656config DEBUG_ATOMIC_SLEEP 657 bool "Sleep inside atomic section checking" 658 select PREEMPT_COUNT 659 depends on DEBUG_KERNEL 660 help 661 If you say Y here, various routines which may sleep will become very 662 noisy if they are called inside atomic sections: when a spinlock is 663 held, inside an rcu read side critical section, inside preempt disabled 664 sections, inside an interrupt, etc... 665 666config DEBUG_LOCKING_API_SELFTESTS 667 bool "Locking API boot-time self-tests" 668 depends on DEBUG_KERNEL 669 help 670 Say Y here if you want the kernel to run a short self-test during 671 bootup. The self-test checks whether common types of locking bugs 672 are detected by debugging mechanisms or not. (if you disable 673 lock debugging then those bugs wont be detected of course.) 674 The following locking APIs are covered: spinlocks, rwlocks, 675 mutexes and rwsems. 676 677config STACKTRACE 678 bool 679 depends on STACKTRACE_SUPPORT 680 681config DEBUG_STACK_USAGE 682 bool "Stack utilization instrumentation" 683 depends on DEBUG_KERNEL 684 help 685 Enables the display of the minimum amount of free stack which each 686 task has ever had available in the sysrq-T and sysrq-P debug output. 687 688 This option will slow down process creation somewhat. 689 690config DEBUG_KOBJECT 691 bool "kobject debugging" 692 depends on DEBUG_KERNEL 693 help 694 If you say Y here, some extra kobject debugging messages will be sent 695 to the syslog. 696 697config DEBUG_HIGHMEM 698 bool "Highmem debugging" 699 depends on DEBUG_KERNEL && HIGHMEM 700 help 701 This options enables addition error checking for high memory systems. 702 Disable for production systems. 703 704config DEBUG_BUGVERBOSE 705 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 706 depends on BUG 707 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 708 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE 709 default y 710 help 711 Say Y here to make BUG() panics output the file name and line number 712 of the BUG call as well as the EIP and oops trace. This aids 713 debugging but costs about 70-100K of memory. 714 715config DEBUG_INFO 716 bool "Compile the kernel with debug info" 717 depends on DEBUG_KERNEL 718 help 719 If you say Y here the resulting kernel image will include 720 debugging info resulting in a larger kernel image. 721 This adds debug symbols to the kernel and modules (gcc -g), and 722 is needed if you intend to use kernel crashdump or binary object 723 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 724 Say Y here only if you plan to debug the kernel. 725 726 If unsure, say N. 727 728config DEBUG_INFO_REDUCED 729 bool "Reduce debugging information" 730 depends on DEBUG_INFO 731 help 732 If you say Y here gcc is instructed to generate less debugging 733 information for structure types. This means that tools that 734 need full debugging information (like kgdb or systemtap) won't 735 be happy. But if you merely need debugging information to 736 resolve line numbers there is no loss. Advantage is that 737 build directory object sizes shrink dramatically over a full 738 DEBUG_INFO build and compile times are reduced too. 739 Only works with newer gcc versions. 740 741config DEBUG_VM 742 bool "Debug VM" 743 depends on DEBUG_KERNEL 744 help 745 Enable this to turn on extended checks in the virtual-memory system 746 that may impact performance. 747 748 If unsure, say N. 749 750config DEBUG_VIRTUAL 751 bool "Debug VM translations" 752 depends on DEBUG_KERNEL && X86 753 help 754 Enable some costly sanity checks in virtual to page code. This can 755 catch mistakes with virt_to_page() and friends. 756 757 If unsure, say N. 758 759config DEBUG_NOMMU_REGIONS 760 bool "Debug the global anon/private NOMMU mapping region tree" 761 depends on DEBUG_KERNEL && !MMU 762 help 763 This option causes the global tree of anonymous and private mapping 764 regions to be regularly checked for invalid topology. 765 766config DEBUG_WRITECOUNT 767 bool "Debug filesystem writers count" 768 depends on DEBUG_KERNEL 769 help 770 Enable this to catch wrong use of the writers count in struct 771 vfsmount. This will increase the size of each file struct by 772 32 bits. 773 774 If unsure, say N. 775 776config DEBUG_MEMORY_INIT 777 bool "Debug memory initialisation" if EXPERT 778 default !EXPERT 779 help 780 Enable this for additional checks during memory initialisation. 781 The sanity checks verify aspects of the VM such as the memory model 782 and other information provided by the architecture. Verbose 783 information will be printed at KERN_DEBUG loglevel depending 784 on the mminit_loglevel= command-line option. 785 786 If unsure, say Y 787 788config DEBUG_LIST 789 bool "Debug linked list manipulation" 790 depends on DEBUG_KERNEL 791 help 792 Enable this to turn on extended checks in the linked-list 793 walking routines. 794 795 If unsure, say N. 796 797config TEST_LIST_SORT 798 bool "Linked list sorting test" 799 depends on DEBUG_KERNEL 800 help 801 Enable this to turn on 'list_sort()' function test. This test is 802 executed only once during system boot, so affects only boot time. 803 804 If unsure, say N. 805 806config DEBUG_SG 807 bool "Debug SG table operations" 808 depends on DEBUG_KERNEL 809 help 810 Enable this to turn on checks on scatter-gather tables. This can 811 help find problems with drivers that do not properly initialize 812 their sg tables. 813 814 If unsure, say N. 815 816config DEBUG_NOTIFIERS 817 bool "Debug notifier call chains" 818 depends on DEBUG_KERNEL 819 help 820 Enable this to turn on sanity checking for notifier call chains. 821 This is most useful for kernel developers to make sure that 822 modules properly unregister themselves from notifier chains. 823 This is a relatively cheap check but if you care about maximum 824 performance, say N. 825 826config DEBUG_CREDENTIALS 827 bool "Debug credential management" 828 depends on DEBUG_KERNEL 829 help 830 Enable this to turn on some debug checking for credential 831 management. The additional code keeps track of the number of 832 pointers from task_structs to any given cred struct, and checks to 833 see that this number never exceeds the usage count of the cred 834 struct. 835 836 Furthermore, if SELinux is enabled, this also checks that the 837 security pointer in the cred struct is never seen to be invalid. 838 839 If unsure, say N. 840 841# 842# Select this config option from the architecture Kconfig, if it 843# is preferred to always offer frame pointers as a config 844# option on the architecture (regardless of KERNEL_DEBUG): 845# 846config ARCH_WANT_FRAME_POINTERS 847 bool 848 help 849 850config FRAME_POINTER 851 bool "Compile the kernel with frame pointers" 852 depends on DEBUG_KERNEL && \ 853 (CRIS || M68K || FRV || UML || \ 854 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 855 ARCH_WANT_FRAME_POINTERS 856 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 857 help 858 If you say Y here the resulting kernel image will be slightly 859 larger and slower, but it gives very useful debugging information 860 in case of kernel bugs. (precise oopses/stacktraces/warnings) 861 862config BOOT_PRINTK_DELAY 863 bool "Delay each boot printk message by N milliseconds" 864 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 865 help 866 This build option allows you to read kernel boot messages 867 by inserting a short delay after each one. The delay is 868 specified in milliseconds on the kernel command line, 869 using "boot_delay=N". 870 871 It is likely that you would also need to use "lpj=M" to preset 872 the "loops per jiffie" value. 873 See a previous boot log for the "lpj" value to use for your 874 system, and then set "lpj=M" before setting "boot_delay=N". 875 NOTE: Using this option may adversely affect SMP systems. 876 I.e., processors other than the first one may not boot up. 877 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 878 what it believes to be lockup conditions. 879 880config RCU_TORTURE_TEST 881 tristate "torture tests for RCU" 882 depends on DEBUG_KERNEL 883 default n 884 help 885 This option provides a kernel module that runs torture tests 886 on the RCU infrastructure. The kernel module may be built 887 after the fact on the running kernel to be tested, if desired. 888 889 Say Y here if you want RCU torture tests to be built into 890 the kernel. 891 Say M if you want the RCU torture tests to build as a module. 892 Say N if you are unsure. 893 894config RCU_TORTURE_TEST_RUNNABLE 895 bool "torture tests for RCU runnable by default" 896 depends on RCU_TORTURE_TEST = y 897 default n 898 help 899 This option provides a way to build the RCU torture tests 900 directly into the kernel without them starting up at boot 901 time. You can use /proc/sys/kernel/rcutorture_runnable 902 to manually override this setting. This /proc file is 903 available only when the RCU torture tests have been built 904 into the kernel. 905 906 Say Y here if you want the RCU torture tests to start during 907 boot (you probably don't). 908 Say N here if you want the RCU torture tests to start only 909 after being manually enabled via /proc. 910 911config RCU_CPU_STALL_TIMEOUT 912 int "RCU CPU stall timeout in seconds" 913 depends on TREE_RCU || TREE_PREEMPT_RCU 914 range 3 300 915 default 60 916 help 917 If a given RCU grace period extends more than the specified 918 number of seconds, a CPU stall warning is printed. If the 919 RCU grace period persists, additional CPU stall warnings are 920 printed at more widely spaced intervals. 921 922config RCU_CPU_STALL_VERBOSE 923 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 924 depends on TREE_PREEMPT_RCU 925 default y 926 help 927 This option causes RCU to printk detailed per-task information 928 for any tasks that are stalling the current RCU grace period. 929 930 Say N if you are unsure. 931 932 Say Y if you want to enable such checks. 933 934config RCU_CPU_STALL_INFO 935 bool "Print additional diagnostics on RCU CPU stall" 936 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 937 default n 938 help 939 For each stalled CPU that is aware of the current RCU grace 940 period, print out additional per-CPU diagnostic information 941 regarding scheduling-clock ticks, idle state, and, 942 for RCU_FAST_NO_HZ kernels, idle-entry state. 943 944 Say N if you are unsure. 945 946 Say Y if you want to enable such diagnostics. 947 948config RCU_TRACE 949 bool "Enable tracing for RCU" 950 depends on DEBUG_KERNEL 951 help 952 This option provides tracing in RCU which presents stats 953 in debugfs for debugging RCU implementation. 954 955 Say Y here if you want to enable RCU tracing 956 Say N if you are unsure. 957 958config KPROBES_SANITY_TEST 959 bool "Kprobes sanity tests" 960 depends on DEBUG_KERNEL 961 depends on KPROBES 962 default n 963 help 964 This option provides for testing basic kprobes functionality on 965 boot. A sample kprobe, jprobe and kretprobe are inserted and 966 verified for functionality. 967 968 Say N if you are unsure. 969 970config BACKTRACE_SELF_TEST 971 tristate "Self test for the backtrace code" 972 depends on DEBUG_KERNEL 973 default n 974 help 975 This option provides a kernel module that can be used to test 976 the kernel stack backtrace code. This option is not useful 977 for distributions or general kernels, but only for kernel 978 developers working on architecture code. 979 980 Note that if you want to also test saved backtraces, you will 981 have to enable STACKTRACE as well. 982 983 Say N if you are unsure. 984 985config DEBUG_BLOCK_EXT_DEVT 986 bool "Force extended block device numbers and spread them" 987 depends on DEBUG_KERNEL 988 depends on BLOCK 989 default n 990 help 991 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 992 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 993 YOU ARE DOING. Distros, please enable this and fix whatever 994 is broken. 995 996 Conventionally, block device numbers are allocated from 997 predetermined contiguous area. However, extended block area 998 may introduce non-contiguous block device numbers. This 999 option forces most block device numbers to be allocated from 1000 the extended space and spreads them to discover kernel or 1001 userland code paths which assume predetermined contiguous 1002 device number allocation. 1003 1004 Note that turning on this debug option shuffles all the 1005 device numbers for all IDE and SCSI devices including libata 1006 ones, so root partition specified using device number 1007 directly (via rdev or root=MAJ:MIN) won't work anymore. 1008 Textual device names (root=/dev/sdXn) will continue to work. 1009 1010 Say N if you are unsure. 1011 1012config DEBUG_FORCE_WEAK_PER_CPU 1013 bool "Force weak per-cpu definitions" 1014 depends on DEBUG_KERNEL 1015 help 1016 s390 and alpha require percpu variables in modules to be 1017 defined weak to work around addressing range issue which 1018 puts the following two restrictions on percpu variable 1019 definitions. 1020 1021 1. percpu symbols must be unique whether static or not 1022 2. percpu variables can't be defined inside a function 1023 1024 To ensure that generic code follows the above rules, this 1025 option forces all percpu variables to be defined as weak. 1026 1027config DEBUG_PER_CPU_MAPS 1028 bool "Debug access to per_cpu maps" 1029 depends on DEBUG_KERNEL 1030 depends on SMP 1031 help 1032 Say Y to verify that the per_cpu map being accessed has 1033 been set up. This adds a fair amount of code to kernel memory 1034 and decreases performance. 1035 1036 Say N if unsure. 1037 1038config LKDTM 1039 tristate "Linux Kernel Dump Test Tool Module" 1040 depends on DEBUG_FS 1041 depends on BLOCK 1042 default n 1043 help 1044 This module enables testing of the different dumping mechanisms by 1045 inducing system failures at predefined crash points. 1046 If you don't need it: say N 1047 Choose M here to compile this code as a module. The module will be 1048 called lkdtm. 1049 1050 Documentation on how to use the module can be found in 1051 Documentation/fault-injection/provoke-crashes.txt 1052 1053config CPU_NOTIFIER_ERROR_INJECT 1054 tristate "CPU notifier error injection module" 1055 depends on HOTPLUG_CPU && DEBUG_KERNEL 1056 help 1057 This option provides a kernel module that can be used to test 1058 the error handling of the cpu notifiers 1059 1060 To compile this code as a module, choose M here: the module will 1061 be called cpu-notifier-error-inject. 1062 1063 If unsure, say N. 1064 1065config FAULT_INJECTION 1066 bool "Fault-injection framework" 1067 depends on DEBUG_KERNEL 1068 help 1069 Provide fault-injection framework. 1070 For more details, see Documentation/fault-injection/. 1071 1072config FAILSLAB 1073 bool "Fault-injection capability for kmalloc" 1074 depends on FAULT_INJECTION 1075 depends on SLAB || SLUB 1076 help 1077 Provide fault-injection capability for kmalloc. 1078 1079config FAIL_PAGE_ALLOC 1080 bool "Fault-injection capabilitiy for alloc_pages()" 1081 depends on FAULT_INJECTION 1082 help 1083 Provide fault-injection capability for alloc_pages(). 1084 1085config FAIL_MAKE_REQUEST 1086 bool "Fault-injection capability for disk IO" 1087 depends on FAULT_INJECTION && BLOCK 1088 help 1089 Provide fault-injection capability for disk IO. 1090 1091config FAIL_IO_TIMEOUT 1092 bool "Fault-injection capability for faking disk interrupts" 1093 depends on FAULT_INJECTION && BLOCK 1094 help 1095 Provide fault-injection capability on end IO handling. This 1096 will make the block layer "forget" an interrupt as configured, 1097 thus exercising the error handling. 1098 1099 Only works with drivers that use the generic timeout handling, 1100 for others it wont do anything. 1101 1102config FAIL_MMC_REQUEST 1103 bool "Fault-injection capability for MMC IO" 1104 select DEBUG_FS 1105 depends on FAULT_INJECTION && MMC 1106 help 1107 Provide fault-injection capability for MMC IO. 1108 This will make the mmc core return data errors. This is 1109 useful to test the error handling in the mmc block device 1110 and to test how the mmc host driver handles retries from 1111 the block device. 1112 1113config FAULT_INJECTION_DEBUG_FS 1114 bool "Debugfs entries for fault-injection capabilities" 1115 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1116 help 1117 Enable configuration of fault-injection capabilities via debugfs. 1118 1119config FAULT_INJECTION_STACKTRACE_FILTER 1120 bool "stacktrace filter for fault-injection capabilities" 1121 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1122 depends on !X86_64 1123 select STACKTRACE 1124 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1125 help 1126 Provide stacktrace filter for fault-injection capabilities 1127 1128config LATENCYTOP 1129 bool "Latency measuring infrastructure" 1130 depends on HAVE_LATENCYTOP_SUPPORT 1131 depends on DEBUG_KERNEL 1132 depends on STACKTRACE_SUPPORT 1133 depends on PROC_FS 1134 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1135 select KALLSYMS 1136 select KALLSYMS_ALL 1137 select STACKTRACE 1138 select SCHEDSTATS 1139 select SCHED_DEBUG 1140 help 1141 Enable this option if you want to use the LatencyTOP tool 1142 to find out which userspace is blocking on what kernel operations. 1143 1144source mm/Kconfig.debug 1145source kernel/trace/Kconfig 1146 1147config PROVIDE_OHCI1394_DMA_INIT 1148 bool "Remote debugging over FireWire early on boot" 1149 depends on PCI && X86 1150 help 1151 If you want to debug problems which hang or crash the kernel early 1152 on boot and the crashing machine has a FireWire port, you can use 1153 this feature to remotely access the memory of the crashed machine 1154 over FireWire. This employs remote DMA as part of the OHCI1394 1155 specification which is now the standard for FireWire controllers. 1156 1157 With remote DMA, you can monitor the printk buffer remotely using 1158 firescope and access all memory below 4GB using fireproxy from gdb. 1159 Even controlling a kernel debugger is possible using remote DMA. 1160 1161 Usage: 1162 1163 If ohci1394_dma=early is used as boot parameter, it will initialize 1164 all OHCI1394 controllers which are found in the PCI config space. 1165 1166 As all changes to the FireWire bus such as enabling and disabling 1167 devices cause a bus reset and thereby disable remote DMA for all 1168 devices, be sure to have the cable plugged and FireWire enabled on 1169 the debugging host before booting the debug target for debugging. 1170 1171 This code (~1k) is freed after boot. By then, the firewire stack 1172 in charge of the OHCI-1394 controllers should be used instead. 1173 1174 See Documentation/debugging-via-ohci1394.txt for more information. 1175 1176config FIREWIRE_OHCI_REMOTE_DMA 1177 bool "Remote debugging over FireWire with firewire-ohci" 1178 depends on FIREWIRE_OHCI 1179 help 1180 This option lets you use the FireWire bus for remote debugging 1181 with help of the firewire-ohci driver. It enables unfiltered 1182 remote DMA in firewire-ohci. 1183 See Documentation/debugging-via-ohci1394.txt for more information. 1184 1185 If unsure, say N. 1186 1187config BUILD_DOCSRC 1188 bool "Build targets in Documentation/ tree" 1189 depends on HEADERS_CHECK 1190 help 1191 This option attempts to build objects from the source files in the 1192 kernel Documentation/ tree. 1193 1194 Say N if you are unsure. 1195 1196config DYNAMIC_DEBUG 1197 bool "Enable dynamic printk() support" 1198 default n 1199 depends on PRINTK 1200 depends on DEBUG_FS 1201 help 1202 1203 Compiles debug level messages into the kernel, which would not 1204 otherwise be available at runtime. These messages can then be 1205 enabled/disabled based on various levels of scope - per source file, 1206 function, module, format string, and line number. This mechanism 1207 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1208 this compile option is a larger kernel text size of about 2%. 1209 1210 Usage: 1211 1212 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1213 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1214 filesystem must first be mounted before making use of this feature. 1215 We refer the control file as: <debugfs>/dynamic_debug/control. This 1216 file contains a list of the debug statements that can be enabled. The 1217 format for each line of the file is: 1218 1219 filename:lineno [module]function flags format 1220 1221 filename : source file of the debug statement 1222 lineno : line number of the debug statement 1223 module : module that contains the debug statement 1224 function : function that contains the debug statement 1225 flags : 'p' means the line is turned 'on' for printing 1226 format : the format used for the debug statement 1227 1228 From a live system: 1229 1230 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1231 # filename:lineno [module]function flags format 1232 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1233 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1234 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1235 1236 Example usage: 1237 1238 // enable the message at line 1603 of file svcsock.c 1239 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1240 <debugfs>/dynamic_debug/control 1241 1242 // enable all the messages in file svcsock.c 1243 nullarbor:~ # echo -n 'file svcsock.c +p' > 1244 <debugfs>/dynamic_debug/control 1245 1246 // enable all the messages in the NFS server module 1247 nullarbor:~ # echo -n 'module nfsd +p' > 1248 <debugfs>/dynamic_debug/control 1249 1250 // enable all 12 messages in the function svc_process() 1251 nullarbor:~ # echo -n 'func svc_process +p' > 1252 <debugfs>/dynamic_debug/control 1253 1254 // disable all 12 messages in the function svc_process() 1255 nullarbor:~ # echo -n 'func svc_process -p' > 1256 <debugfs>/dynamic_debug/control 1257 1258 See Documentation/dynamic-debug-howto.txt for additional information. 1259 1260config DMA_API_DEBUG 1261 bool "Enable debugging of DMA-API usage" 1262 depends on HAVE_DMA_API_DEBUG 1263 help 1264 Enable this option to debug the use of the DMA API by device drivers. 1265 With this option you will be able to detect common bugs in device 1266 drivers like double-freeing of DMA mappings or freeing mappings that 1267 were never allocated. 1268 This option causes a performance degredation. Use only if you want 1269 to debug device drivers. If unsure, say N. 1270 1271config ATOMIC64_SELFTEST 1272 bool "Perform an atomic64_t self-test at boot" 1273 help 1274 Enable this option to test the atomic64_t functions at boot. 1275 1276 If unsure, say N. 1277 1278config ASYNC_RAID6_TEST 1279 tristate "Self test for hardware accelerated raid6 recovery" 1280 depends on ASYNC_RAID6_RECOV 1281 select ASYNC_MEMCPY 1282 ---help--- 1283 This is a one-shot self test that permutes through the 1284 recovery of all the possible two disk failure scenarios for a 1285 N-disk array. Recovery is performed with the asynchronous 1286 raid6 recovery routines, and will optionally use an offload 1287 engine if one is available. 1288 1289 If unsure, say N. 1290 1291source "samples/Kconfig" 1292 1293source "lib/Kconfig.kgdb" 1294 1295source "lib/Kconfig.kmemcheck" 1296 1297config TEST_KSTRTOX 1298 tristate "Test kstrto*() family of functions at runtime" 1299