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 select UNINLINE_SPIN_UNLOCK 503 help 504 Say Y here and build SMP to catch missing spinlock initialization 505 and certain other kinds of spinlock errors commonly made. This is 506 best used in conjunction with the NMI watchdog so that spinlock 507 deadlocks are also debuggable. 508 509config DEBUG_MUTEXES 510 bool "Mutex debugging: basic checks" 511 depends on DEBUG_KERNEL 512 help 513 This feature allows mutex semantics violations to be detected and 514 reported. 515 516config DEBUG_LOCK_ALLOC 517 bool "Lock debugging: detect incorrect freeing of live locks" 518 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 519 select DEBUG_SPINLOCK 520 select DEBUG_MUTEXES 521 select LOCKDEP 522 help 523 This feature will check whether any held lock (spinlock, rwlock, 524 mutex or rwsem) is incorrectly freed by the kernel, via any of the 525 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 526 vfree(), etc.), whether a live lock is incorrectly reinitialized via 527 spin_lock_init()/mutex_init()/etc., or whether there is any lock 528 held during task exit. 529 530config PROVE_LOCKING 531 bool "Lock debugging: prove locking correctness" 532 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 533 select LOCKDEP 534 select DEBUG_SPINLOCK 535 select DEBUG_MUTEXES 536 select DEBUG_LOCK_ALLOC 537 select TRACE_IRQFLAGS 538 default n 539 help 540 This feature enables the kernel to prove that all locking 541 that occurs in the kernel runtime is mathematically 542 correct: that under no circumstance could an arbitrary (and 543 not yet triggered) combination of observed locking 544 sequences (on an arbitrary number of CPUs, running an 545 arbitrary number of tasks and interrupt contexts) cause a 546 deadlock. 547 548 In short, this feature enables the kernel to report locking 549 related deadlocks before they actually occur. 550 551 The proof does not depend on how hard and complex a 552 deadlock scenario would be to trigger: how many 553 participant CPUs, tasks and irq-contexts would be needed 554 for it to trigger. The proof also does not depend on 555 timing: if a race and a resulting deadlock is possible 556 theoretically (no matter how unlikely the race scenario 557 is), it will be proven so and will immediately be 558 reported by the kernel (once the event is observed that 559 makes the deadlock theoretically possible). 560 561 If a deadlock is impossible (i.e. the locking rules, as 562 observed by the kernel, are mathematically correct), the 563 kernel reports nothing. 564 565 NOTE: this feature can also be enabled for rwlocks, mutexes 566 and rwsems - in which case all dependencies between these 567 different locking variants are observed and mapped too, and 568 the proof of observed correctness is also maintained for an 569 arbitrary combination of these separate locking variants. 570 571 For more details, see Documentation/lockdep-design.txt. 572 573config PROVE_RCU 574 bool "RCU debugging: prove RCU correctness" 575 depends on PROVE_LOCKING 576 default n 577 help 578 This feature enables lockdep extensions that check for correct 579 use of RCU APIs. This is currently under development. Say Y 580 if you want to debug RCU usage or help work on the PROVE_RCU 581 feature. 582 583 Say N if you are unsure. 584 585config PROVE_RCU_REPEATEDLY 586 bool "RCU debugging: don't disable PROVE_RCU on first splat" 587 depends on PROVE_RCU 588 default n 589 help 590 By itself, PROVE_RCU will disable checking upon issuing the 591 first warning (or "splat"). This feature prevents such 592 disabling, allowing multiple RCU-lockdep warnings to be printed 593 on a single reboot. 594 595 Say Y to allow multiple RCU-lockdep warnings per boot. 596 597 Say N if you are unsure. 598 599config SPARSE_RCU_POINTER 600 bool "RCU debugging: sparse-based checks for pointer usage" 601 default n 602 help 603 This feature enables the __rcu sparse annotation for 604 RCU-protected pointers. This annotation will cause sparse 605 to flag any non-RCU used of annotated pointers. This can be 606 helpful when debugging RCU usage. Please note that this feature 607 is not intended to enforce code cleanliness; it is instead merely 608 a debugging aid. 609 610 Say Y to make sparse flag questionable use of RCU-protected pointers 611 612 Say N if you are unsure. 613 614config LOCKDEP 615 bool 616 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 617 select STACKTRACE 618 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE 619 select KALLSYMS 620 select KALLSYMS_ALL 621 622config LOCK_STAT 623 bool "Lock usage statistics" 624 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 625 select LOCKDEP 626 select DEBUG_SPINLOCK 627 select DEBUG_MUTEXES 628 select DEBUG_LOCK_ALLOC 629 default n 630 help 631 This feature enables tracking lock contention points 632 633 For more details, see Documentation/lockstat.txt 634 635 This also enables lock events required by "perf lock", 636 subcommand of perf. 637 If you want to use "perf lock", you also need to turn on 638 CONFIG_EVENT_TRACING. 639 640 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 641 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 642 643config DEBUG_LOCKDEP 644 bool "Lock dependency engine debugging" 645 depends on DEBUG_KERNEL && LOCKDEP 646 help 647 If you say Y here, the lock dependency engine will do 648 additional runtime checks to debug itself, at the price 649 of more runtime overhead. 650 651config TRACE_IRQFLAGS 652 bool 653 help 654 Enables hooks to interrupt enabling and disabling for 655 either tracing or lock debugging. 656 657config DEBUG_ATOMIC_SLEEP 658 bool "Sleep inside atomic section checking" 659 select PREEMPT_COUNT 660 depends on DEBUG_KERNEL 661 help 662 If you say Y here, various routines which may sleep will become very 663 noisy if they are called inside atomic sections: when a spinlock is 664 held, inside an rcu read side critical section, inside preempt disabled 665 sections, inside an interrupt, etc... 666 667config DEBUG_LOCKING_API_SELFTESTS 668 bool "Locking API boot-time self-tests" 669 depends on DEBUG_KERNEL 670 help 671 Say Y here if you want the kernel to run a short self-test during 672 bootup. The self-test checks whether common types of locking bugs 673 are detected by debugging mechanisms or not. (if you disable 674 lock debugging then those bugs wont be detected of course.) 675 The following locking APIs are covered: spinlocks, rwlocks, 676 mutexes and rwsems. 677 678config STACKTRACE 679 bool 680 depends on STACKTRACE_SUPPORT 681 682config DEBUG_STACK_USAGE 683 bool "Stack utilization instrumentation" 684 depends on DEBUG_KERNEL 685 help 686 Enables the display of the minimum amount of free stack which each 687 task has ever had available in the sysrq-T and sysrq-P debug output. 688 689 This option will slow down process creation somewhat. 690 691config DEBUG_KOBJECT 692 bool "kobject debugging" 693 depends on DEBUG_KERNEL 694 help 695 If you say Y here, some extra kobject debugging messages will be sent 696 to the syslog. 697 698config DEBUG_HIGHMEM 699 bool "Highmem debugging" 700 depends on DEBUG_KERNEL && HIGHMEM 701 help 702 This options enables addition error checking for high memory systems. 703 Disable for production systems. 704 705config DEBUG_BUGVERBOSE 706 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 707 depends on BUG 708 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || \ 709 FRV || SUPERH || GENERIC_BUG || BLACKFIN || MN10300 || TILE 710 default y 711 help 712 Say Y here to make BUG() panics output the file name and line number 713 of the BUG call as well as the EIP and oops trace. This aids 714 debugging but costs about 70-100K of memory. 715 716config DEBUG_INFO 717 bool "Compile the kernel with debug info" 718 depends on DEBUG_KERNEL 719 help 720 If you say Y here the resulting kernel image will include 721 debugging info resulting in a larger kernel image. 722 This adds debug symbols to the kernel and modules (gcc -g), and 723 is needed if you intend to use kernel crashdump or binary object 724 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 725 Say Y here only if you plan to debug the kernel. 726 727 If unsure, say N. 728 729config DEBUG_INFO_REDUCED 730 bool "Reduce debugging information" 731 depends on DEBUG_INFO 732 help 733 If you say Y here gcc is instructed to generate less debugging 734 information for structure types. This means that tools that 735 need full debugging information (like kgdb or systemtap) won't 736 be happy. But if you merely need debugging information to 737 resolve line numbers there is no loss. Advantage is that 738 build directory object sizes shrink dramatically over a full 739 DEBUG_INFO build and compile times are reduced too. 740 Only works with newer gcc versions. 741 742config DEBUG_VM 743 bool "Debug VM" 744 depends on DEBUG_KERNEL 745 help 746 Enable this to turn on extended checks in the virtual-memory system 747 that may impact performance. 748 749 If unsure, say N. 750 751config DEBUG_VIRTUAL 752 bool "Debug VM translations" 753 depends on DEBUG_KERNEL && X86 754 help 755 Enable some costly sanity checks in virtual to page code. This can 756 catch mistakes with virt_to_page() and friends. 757 758 If unsure, say N. 759 760config DEBUG_NOMMU_REGIONS 761 bool "Debug the global anon/private NOMMU mapping region tree" 762 depends on DEBUG_KERNEL && !MMU 763 help 764 This option causes the global tree of anonymous and private mapping 765 regions to be regularly checked for invalid topology. 766 767config DEBUG_WRITECOUNT 768 bool "Debug filesystem writers count" 769 depends on DEBUG_KERNEL 770 help 771 Enable this to catch wrong use of the writers count in struct 772 vfsmount. This will increase the size of each file struct by 773 32 bits. 774 775 If unsure, say N. 776 777config DEBUG_MEMORY_INIT 778 bool "Debug memory initialisation" if EXPERT 779 default !EXPERT 780 help 781 Enable this for additional checks during memory initialisation. 782 The sanity checks verify aspects of the VM such as the memory model 783 and other information provided by the architecture. Verbose 784 information will be printed at KERN_DEBUG loglevel depending 785 on the mminit_loglevel= command-line option. 786 787 If unsure, say Y 788 789config DEBUG_LIST 790 bool "Debug linked list manipulation" 791 depends on DEBUG_KERNEL 792 help 793 Enable this to turn on extended checks in the linked-list 794 walking routines. 795 796 If unsure, say N. 797 798config TEST_LIST_SORT 799 bool "Linked list sorting test" 800 depends on DEBUG_KERNEL 801 help 802 Enable this to turn on 'list_sort()' function test. This test is 803 executed only once during system boot, so affects only boot time. 804 805 If unsure, say N. 806 807config DEBUG_SG 808 bool "Debug SG table operations" 809 depends on DEBUG_KERNEL 810 help 811 Enable this to turn on checks on scatter-gather tables. This can 812 help find problems with drivers that do not properly initialize 813 their sg tables. 814 815 If unsure, say N. 816 817config DEBUG_NOTIFIERS 818 bool "Debug notifier call chains" 819 depends on DEBUG_KERNEL 820 help 821 Enable this to turn on sanity checking for notifier call chains. 822 This is most useful for kernel developers to make sure that 823 modules properly unregister themselves from notifier chains. 824 This is a relatively cheap check but if you care about maximum 825 performance, say N. 826 827config DEBUG_CREDENTIALS 828 bool "Debug credential management" 829 depends on DEBUG_KERNEL 830 help 831 Enable this to turn on some debug checking for credential 832 management. The additional code keeps track of the number of 833 pointers from task_structs to any given cred struct, and checks to 834 see that this number never exceeds the usage count of the cred 835 struct. 836 837 Furthermore, if SELinux is enabled, this also checks that the 838 security pointer in the cred struct is never seen to be invalid. 839 840 If unsure, say N. 841 842# 843# Select this config option from the architecture Kconfig, if it 844# is preferred to always offer frame pointers as a config 845# option on the architecture (regardless of KERNEL_DEBUG): 846# 847config ARCH_WANT_FRAME_POINTERS 848 bool 849 help 850 851config FRAME_POINTER 852 bool "Compile the kernel with frame pointers" 853 depends on DEBUG_KERNEL && \ 854 (CRIS || M68K || FRV || UML || \ 855 AVR32 || SUPERH || BLACKFIN || MN10300) || \ 856 ARCH_WANT_FRAME_POINTERS 857 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 858 help 859 If you say Y here the resulting kernel image will be slightly 860 larger and slower, but it gives very useful debugging information 861 in case of kernel bugs. (precise oopses/stacktraces/warnings) 862 863config BOOT_PRINTK_DELAY 864 bool "Delay each boot printk message by N milliseconds" 865 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 866 help 867 This build option allows you to read kernel boot messages 868 by inserting a short delay after each one. The delay is 869 specified in milliseconds on the kernel command line, 870 using "boot_delay=N". 871 872 It is likely that you would also need to use "lpj=M" to preset 873 the "loops per jiffie" value. 874 See a previous boot log for the "lpj" value to use for your 875 system, and then set "lpj=M" before setting "boot_delay=N". 876 NOTE: Using this option may adversely affect SMP systems. 877 I.e., processors other than the first one may not boot up. 878 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 879 what it believes to be lockup conditions. 880 881config RCU_TORTURE_TEST 882 tristate "torture tests for RCU" 883 depends on DEBUG_KERNEL 884 default n 885 help 886 This option provides a kernel module that runs torture tests 887 on the RCU infrastructure. The kernel module may be built 888 after the fact on the running kernel to be tested, if desired. 889 890 Say Y here if you want RCU torture tests to be built into 891 the kernel. 892 Say M if you want the RCU torture tests to build as a module. 893 Say N if you are unsure. 894 895config RCU_TORTURE_TEST_RUNNABLE 896 bool "torture tests for RCU runnable by default" 897 depends on RCU_TORTURE_TEST = y 898 default n 899 help 900 This option provides a way to build the RCU torture tests 901 directly into the kernel without them starting up at boot 902 time. You can use /proc/sys/kernel/rcutorture_runnable 903 to manually override this setting. This /proc file is 904 available only when the RCU torture tests have been built 905 into the kernel. 906 907 Say Y here if you want the RCU torture tests to start during 908 boot (you probably don't). 909 Say N here if you want the RCU torture tests to start only 910 after being manually enabled via /proc. 911 912config RCU_CPU_STALL_TIMEOUT 913 int "RCU CPU stall timeout in seconds" 914 depends on TREE_RCU || TREE_PREEMPT_RCU 915 range 3 300 916 default 60 917 help 918 If a given RCU grace period extends more than the specified 919 number of seconds, a CPU stall warning is printed. If the 920 RCU grace period persists, additional CPU stall warnings are 921 printed at more widely spaced intervals. 922 923config RCU_CPU_STALL_VERBOSE 924 bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR" 925 depends on TREE_PREEMPT_RCU 926 default y 927 help 928 This option causes RCU to printk detailed per-task information 929 for any tasks that are stalling the current RCU grace period. 930 931 Say N if you are unsure. 932 933 Say Y if you want to enable such checks. 934 935config RCU_CPU_STALL_INFO 936 bool "Print additional diagnostics on RCU CPU stall" 937 depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL 938 default n 939 help 940 For each stalled CPU that is aware of the current RCU grace 941 period, print out additional per-CPU diagnostic information 942 regarding scheduling-clock ticks, idle state, and, 943 for RCU_FAST_NO_HZ kernels, idle-entry state. 944 945 Say N if you are unsure. 946 947 Say Y if you want to enable such diagnostics. 948 949config RCU_TRACE 950 bool "Enable tracing for RCU" 951 depends on DEBUG_KERNEL 952 help 953 This option provides tracing in RCU which presents stats 954 in debugfs for debugging RCU implementation. 955 956 Say Y here if you want to enable RCU tracing 957 Say N if you are unsure. 958 959config KPROBES_SANITY_TEST 960 bool "Kprobes sanity tests" 961 depends on DEBUG_KERNEL 962 depends on KPROBES 963 default n 964 help 965 This option provides for testing basic kprobes functionality on 966 boot. A sample kprobe, jprobe and kretprobe are inserted and 967 verified for functionality. 968 969 Say N if you are unsure. 970 971config BACKTRACE_SELF_TEST 972 tristate "Self test for the backtrace code" 973 depends on DEBUG_KERNEL 974 default n 975 help 976 This option provides a kernel module that can be used to test 977 the kernel stack backtrace code. This option is not useful 978 for distributions or general kernels, but only for kernel 979 developers working on architecture code. 980 981 Note that if you want to also test saved backtraces, you will 982 have to enable STACKTRACE as well. 983 984 Say N if you are unsure. 985 986config DEBUG_BLOCK_EXT_DEVT 987 bool "Force extended block device numbers and spread them" 988 depends on DEBUG_KERNEL 989 depends on BLOCK 990 default n 991 help 992 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 993 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 994 YOU ARE DOING. Distros, please enable this and fix whatever 995 is broken. 996 997 Conventionally, block device numbers are allocated from 998 predetermined contiguous area. However, extended block area 999 may introduce non-contiguous block device numbers. This 1000 option forces most block device numbers to be allocated from 1001 the extended space and spreads them to discover kernel or 1002 userland code paths which assume predetermined contiguous 1003 device number allocation. 1004 1005 Note that turning on this debug option shuffles all the 1006 device numbers for all IDE and SCSI devices including libata 1007 ones, so root partition specified using device number 1008 directly (via rdev or root=MAJ:MIN) won't work anymore. 1009 Textual device names (root=/dev/sdXn) will continue to work. 1010 1011 Say N if you are unsure. 1012 1013config DEBUG_FORCE_WEAK_PER_CPU 1014 bool "Force weak per-cpu definitions" 1015 depends on DEBUG_KERNEL 1016 help 1017 s390 and alpha require percpu variables in modules to be 1018 defined weak to work around addressing range issue which 1019 puts the following two restrictions on percpu variable 1020 definitions. 1021 1022 1. percpu symbols must be unique whether static or not 1023 2. percpu variables can't be defined inside a function 1024 1025 To ensure that generic code follows the above rules, this 1026 option forces all percpu variables to be defined as weak. 1027 1028config DEBUG_PER_CPU_MAPS 1029 bool "Debug access to per_cpu maps" 1030 depends on DEBUG_KERNEL 1031 depends on SMP 1032 help 1033 Say Y to verify that the per_cpu map being accessed has 1034 been set up. This adds a fair amount of code to kernel memory 1035 and decreases performance. 1036 1037 Say N if unsure. 1038 1039config LKDTM 1040 tristate "Linux Kernel Dump Test Tool Module" 1041 depends on DEBUG_FS 1042 depends on BLOCK 1043 default n 1044 help 1045 This module enables testing of the different dumping mechanisms by 1046 inducing system failures at predefined crash points. 1047 If you don't need it: say N 1048 Choose M here to compile this code as a module. The module will be 1049 called lkdtm. 1050 1051 Documentation on how to use the module can be found in 1052 Documentation/fault-injection/provoke-crashes.txt 1053 1054config CPU_NOTIFIER_ERROR_INJECT 1055 tristate "CPU notifier error injection module" 1056 depends on HOTPLUG_CPU && DEBUG_KERNEL 1057 help 1058 This option provides a kernel module that can be used to test 1059 the error handling of the cpu notifiers 1060 1061 To compile this code as a module, choose M here: the module will 1062 be called cpu-notifier-error-inject. 1063 1064 If unsure, say N. 1065 1066config FAULT_INJECTION 1067 bool "Fault-injection framework" 1068 depends on DEBUG_KERNEL 1069 help 1070 Provide fault-injection framework. 1071 For more details, see Documentation/fault-injection/. 1072 1073config FAILSLAB 1074 bool "Fault-injection capability for kmalloc" 1075 depends on FAULT_INJECTION 1076 depends on SLAB || SLUB 1077 help 1078 Provide fault-injection capability for kmalloc. 1079 1080config FAIL_PAGE_ALLOC 1081 bool "Fault-injection capabilitiy for alloc_pages()" 1082 depends on FAULT_INJECTION 1083 help 1084 Provide fault-injection capability for alloc_pages(). 1085 1086config FAIL_MAKE_REQUEST 1087 bool "Fault-injection capability for disk IO" 1088 depends on FAULT_INJECTION && BLOCK 1089 help 1090 Provide fault-injection capability for disk IO. 1091 1092config FAIL_IO_TIMEOUT 1093 bool "Fault-injection capability for faking disk interrupts" 1094 depends on FAULT_INJECTION && BLOCK 1095 help 1096 Provide fault-injection capability on end IO handling. This 1097 will make the block layer "forget" an interrupt as configured, 1098 thus exercising the error handling. 1099 1100 Only works with drivers that use the generic timeout handling, 1101 for others it wont do anything. 1102 1103config FAIL_MMC_REQUEST 1104 bool "Fault-injection capability for MMC IO" 1105 select DEBUG_FS 1106 depends on FAULT_INJECTION && MMC 1107 help 1108 Provide fault-injection capability for MMC IO. 1109 This will make the mmc core return data errors. This is 1110 useful to test the error handling in the mmc block device 1111 and to test how the mmc host driver handles retries from 1112 the block device. 1113 1114config FAULT_INJECTION_DEBUG_FS 1115 bool "Debugfs entries for fault-injection capabilities" 1116 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1117 help 1118 Enable configuration of fault-injection capabilities via debugfs. 1119 1120config FAULT_INJECTION_STACKTRACE_FILTER 1121 bool "stacktrace filter for fault-injection capabilities" 1122 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1123 depends on !X86_64 1124 select STACKTRACE 1125 select FRAME_POINTER if !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1126 help 1127 Provide stacktrace filter for fault-injection capabilities 1128 1129config LATENCYTOP 1130 bool "Latency measuring infrastructure" 1131 depends on HAVE_LATENCYTOP_SUPPORT 1132 depends on DEBUG_KERNEL 1133 depends on STACKTRACE_SUPPORT 1134 depends on PROC_FS 1135 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND 1136 select KALLSYMS 1137 select KALLSYMS_ALL 1138 select STACKTRACE 1139 select SCHEDSTATS 1140 select SCHED_DEBUG 1141 help 1142 Enable this option if you want to use the LatencyTOP tool 1143 to find out which userspace is blocking on what kernel operations. 1144 1145source mm/Kconfig.debug 1146source kernel/trace/Kconfig 1147 1148config PROVIDE_OHCI1394_DMA_INIT 1149 bool "Remote debugging over FireWire early on boot" 1150 depends on PCI && X86 1151 help 1152 If you want to debug problems which hang or crash the kernel early 1153 on boot and the crashing machine has a FireWire port, you can use 1154 this feature to remotely access the memory of the crashed machine 1155 over FireWire. This employs remote DMA as part of the OHCI1394 1156 specification which is now the standard for FireWire controllers. 1157 1158 With remote DMA, you can monitor the printk buffer remotely using 1159 firescope and access all memory below 4GB using fireproxy from gdb. 1160 Even controlling a kernel debugger is possible using remote DMA. 1161 1162 Usage: 1163 1164 If ohci1394_dma=early is used as boot parameter, it will initialize 1165 all OHCI1394 controllers which are found in the PCI config space. 1166 1167 As all changes to the FireWire bus such as enabling and disabling 1168 devices cause a bus reset and thereby disable remote DMA for all 1169 devices, be sure to have the cable plugged and FireWire enabled on 1170 the debugging host before booting the debug target for debugging. 1171 1172 This code (~1k) is freed after boot. By then, the firewire stack 1173 in charge of the OHCI-1394 controllers should be used instead. 1174 1175 See Documentation/debugging-via-ohci1394.txt for more information. 1176 1177config FIREWIRE_OHCI_REMOTE_DMA 1178 bool "Remote debugging over FireWire with firewire-ohci" 1179 depends on FIREWIRE_OHCI 1180 help 1181 This option lets you use the FireWire bus for remote debugging 1182 with help of the firewire-ohci driver. It enables unfiltered 1183 remote DMA in firewire-ohci. 1184 See Documentation/debugging-via-ohci1394.txt for more information. 1185 1186 If unsure, say N. 1187 1188config BUILD_DOCSRC 1189 bool "Build targets in Documentation/ tree" 1190 depends on HEADERS_CHECK 1191 help 1192 This option attempts to build objects from the source files in the 1193 kernel Documentation/ tree. 1194 1195 Say N if you are unsure. 1196 1197config DYNAMIC_DEBUG 1198 bool "Enable dynamic printk() support" 1199 default n 1200 depends on PRINTK 1201 depends on DEBUG_FS 1202 help 1203 1204 Compiles debug level messages into the kernel, which would not 1205 otherwise be available at runtime. These messages can then be 1206 enabled/disabled based on various levels of scope - per source file, 1207 function, module, format string, and line number. This mechanism 1208 implicitly enables all pr_debug() and dev_dbg() calls. The impact of 1209 this compile option is a larger kernel text size of about 2%. 1210 1211 Usage: 1212 1213 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 1214 which is contained in the 'debugfs' filesystem. Thus, the debugfs 1215 filesystem must first be mounted before making use of this feature. 1216 We refer the control file as: <debugfs>/dynamic_debug/control. This 1217 file contains a list of the debug statements that can be enabled. The 1218 format for each line of the file is: 1219 1220 filename:lineno [module]function flags format 1221 1222 filename : source file of the debug statement 1223 lineno : line number of the debug statement 1224 module : module that contains the debug statement 1225 function : function that contains the debug statement 1226 flags : 'p' means the line is turned 'on' for printing 1227 format : the format used for the debug statement 1228 1229 From a live system: 1230 1231 nullarbor:~ # cat <debugfs>/dynamic_debug/control 1232 # filename:lineno [module]function flags format 1233 fs/aio.c:222 [aio]__put_ioctx - "__put_ioctx:\040freeing\040%p\012" 1234 fs/aio.c:248 [aio]ioctx_alloc - "ENOMEM:\040nr_events\040too\040high\012" 1235 fs/aio.c:1770 [aio]sys_io_cancel - "calling\040cancel\012" 1236 1237 Example usage: 1238 1239 // enable the message at line 1603 of file svcsock.c 1240 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 1241 <debugfs>/dynamic_debug/control 1242 1243 // enable all the messages in file svcsock.c 1244 nullarbor:~ # echo -n 'file svcsock.c +p' > 1245 <debugfs>/dynamic_debug/control 1246 1247 // enable all the messages in the NFS server module 1248 nullarbor:~ # echo -n 'module nfsd +p' > 1249 <debugfs>/dynamic_debug/control 1250 1251 // enable all 12 messages in the function svc_process() 1252 nullarbor:~ # echo -n 'func svc_process +p' > 1253 <debugfs>/dynamic_debug/control 1254 1255 // disable all 12 messages in the function svc_process() 1256 nullarbor:~ # echo -n 'func svc_process -p' > 1257 <debugfs>/dynamic_debug/control 1258 1259 See Documentation/dynamic-debug-howto.txt for additional information. 1260 1261config DMA_API_DEBUG 1262 bool "Enable debugging of DMA-API usage" 1263 depends on HAVE_DMA_API_DEBUG 1264 help 1265 Enable this option to debug the use of the DMA API by device drivers. 1266 With this option you will be able to detect common bugs in device 1267 drivers like double-freeing of DMA mappings or freeing mappings that 1268 were never allocated. 1269 This option causes a performance degredation. Use only if you want 1270 to debug device drivers. If unsure, say N. 1271 1272config ATOMIC64_SELFTEST 1273 bool "Perform an atomic64_t self-test at boot" 1274 help 1275 Enable this option to test the atomic64_t functions at boot. 1276 1277 If unsure, say N. 1278 1279config ASYNC_RAID6_TEST 1280 tristate "Self test for hardware accelerated raid6 recovery" 1281 depends on ASYNC_RAID6_RECOV 1282 select ASYNC_MEMCPY 1283 ---help--- 1284 This is a one-shot self test that permutes through the 1285 recovery of all the possible two disk failure scenarios for a 1286 N-disk array. Recovery is performed with the asynchronous 1287 raid6 recovery routines, and will optionally use an offload 1288 engine if one is available. 1289 1290 If unsure, say N. 1291 1292source "samples/Kconfig" 1293 1294source "lib/Kconfig.kgdb" 1295 1296source "lib/Kconfig.kmemcheck" 1297 1298config TEST_KSTRTOX 1299 tristate "Test kstrto*() family of functions at runtime" 1300