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