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. 11 12config ENABLE_MUST_CHECK 13 bool "Enable __must_check logic" 14 default y 15 help 16 Enable the __must_check logic in the kernel build. Disable this to 17 suppress the "warning: ignoring return value of 'foo', declared with 18 attribute warn_unused_result" messages. 19 20config MAGIC_SYSRQ 21 bool "Magic SysRq key" 22 depends on !UML 23 help 24 If you say Y here, you will have some control over the system even 25 if the system crashes for example during kernel debugging (e.g., you 26 will be able to flush the buffer cache to disk, reboot the system 27 immediately or dump some status information). This is accomplished 28 by pressing various keys while holding SysRq (Alt+PrintScreen). It 29 also works on a serial console (on PC hardware at least), if you 30 send a BREAK and then within 5 seconds a command keypress. The 31 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 32 unless you really know what this hack does. 33 34config UNUSED_SYMBOLS 35 bool "Enable unused/obsolete exported symbols" 36 default y if X86 37 help 38 Unused but exported symbols make the kernel needlessly bigger. For 39 that reason most of these unused exports will soon be removed. This 40 option is provided temporarily to provide a transition period in case 41 some external kernel module needs one of these symbols anyway. If you 42 encounter such a case in your module, consider if you are actually 43 using the right API. (rationale: since nobody in the kernel is using 44 this in a module, there is a pretty good chance it's actually the 45 wrong interface to use). If you really need the symbol, please send a 46 mail to the linux kernel mailing list mentioning the symbol and why 47 you really need it, and what the merge plan to the mainline kernel for 48 your module is. 49 50config DEBUG_FS 51 bool "Debug Filesystem" 52 depends on SYSFS 53 help 54 debugfs is a virtual file system that kernel developers use to put 55 debugging files into. Enable this option to be able to read and 56 write to these files. 57 58 If unsure, say N. 59 60config HEADERS_CHECK 61 bool "Run 'make headers_check' when building vmlinux" 62 depends on !UML 63 help 64 This option will extract the user-visible kernel headers whenever 65 building the kernel, and will run basic sanity checks on them to 66 ensure that exported files do not attempt to include files which 67 were not exported, etc. 68 69 If you're making modifications to header files which are 70 relevant for userspace, say 'Y', and check the headers 71 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 72 your build tree), to make sure they're suitable. 73 74config DEBUG_KERNEL 75 bool "Kernel debugging" 76 help 77 Say Y here if you are developing drivers or trying to debug and 78 identify kernel problems. 79 80config DEBUG_SHIRQ 81 bool "Debug shared IRQ handlers" 82 depends on DEBUG_KERNEL && GENERIC_HARDIRQS 83 help 84 Enable this to generate a spurious interrupt as soon as a shared 85 interrupt handler is registered, and just before one is deregistered. 86 Drivers ought to be able to handle interrupts coming in at those 87 points; some don't and need to be caught. 88 89config DETECT_SOFTLOCKUP 90 bool "Detect Soft Lockups" 91 depends on DEBUG_KERNEL && !S390 92 default y 93 help 94 Say Y here to enable the kernel to detect "soft lockups", 95 which are bugs that cause the kernel to loop in kernel 96 mode for more than 10 seconds, without giving other tasks a 97 chance to run. 98 99 When a soft-lockup is detected, the kernel will print the 100 current stack trace (which you should report), but the 101 system will stay locked up. This feature has negligible 102 overhead. 103 104 (Note that "hard lockups" are separate type of bugs that 105 can be detected via the NMI-watchdog, on platforms that 106 support it.) 107 108config SCHED_DEBUG 109 bool "Collect scheduler debugging info" 110 depends on DEBUG_KERNEL && PROC_FS 111 default y 112 help 113 If you say Y here, the /proc/sched_debug file will be provided 114 that can help debug the scheduler. The runtime overhead of this 115 option is minimal. 116 117config SCHEDSTATS 118 bool "Collect scheduler statistics" 119 depends on DEBUG_KERNEL && PROC_FS 120 help 121 If you say Y here, additional code will be inserted into the 122 scheduler and related routines to collect statistics about 123 scheduler behavior and provide them in /proc/schedstat. These 124 stats may be useful for both tuning and debugging the scheduler 125 If you aren't debugging the scheduler or trying to tune a specific 126 application, you can say N to avoid the very slight overhead 127 this adds. 128 129config TIMER_STATS 130 bool "Collect kernel timers statistics" 131 depends on DEBUG_KERNEL && PROC_FS 132 help 133 If you say Y here, additional code will be inserted into the 134 timer routines to collect statistics about kernel timers being 135 reprogrammed. The statistics can be read from /proc/timer_stats. 136 The statistics collection is started by writing 1 to /proc/timer_stats, 137 writing 0 stops it. This feature is useful to collect information 138 about timer usage patterns in kernel and userspace. This feature 139 is lightweight if enabled in the kernel config but not activated 140 (it defaults to deactivated on bootup and will only be activated 141 if some application like powertop activates it explicitly). 142 143config DEBUG_SLAB 144 bool "Debug slab memory allocations" 145 depends on DEBUG_KERNEL && SLAB 146 help 147 Say Y here to have the kernel do limited verification on memory 148 allocation as well as poisoning memory on free to catch use of freed 149 memory. This can make kmalloc/kfree-intensive workloads much slower. 150 151config DEBUG_SLAB_LEAK 152 bool "Memory leak debugging" 153 depends on DEBUG_SLAB 154 155config SLUB_DEBUG_ON 156 bool "SLUB debugging on by default" 157 depends on SLUB && SLUB_DEBUG 158 default n 159 help 160 Boot with debugging on by default. SLUB boots by default with 161 the runtime debug capabilities switched off. Enabling this is 162 equivalent to specifying the "slub_debug" parameter on boot. 163 There is no support for more fine grained debug control like 164 possible with slub_debug=xxx. SLUB debugging may be switched 165 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 166 "slub_debug=-". 167 168config DEBUG_PREEMPT 169 bool "Debug preemptible kernel" 170 depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64) 171 default y 172 help 173 If you say Y here then the kernel will use a debug variant of the 174 commonly used smp_processor_id() function and will print warnings 175 if kernel code uses it in a preemption-unsafe way. Also, the kernel 176 will detect preemption count underflows. 177 178config DEBUG_RT_MUTEXES 179 bool "RT Mutex debugging, deadlock detection" 180 depends on DEBUG_KERNEL && RT_MUTEXES 181 help 182 This allows rt mutex semantics violations and rt mutex related 183 deadlocks (lockups) to be detected and reported automatically. 184 185config DEBUG_PI_LIST 186 bool 187 default y 188 depends on DEBUG_RT_MUTEXES 189 190config RT_MUTEX_TESTER 191 bool "Built-in scriptable tester for rt-mutexes" 192 depends on DEBUG_KERNEL && RT_MUTEXES 193 help 194 This option enables a rt-mutex tester. 195 196config DEBUG_SPINLOCK 197 bool "Spinlock and rw-lock debugging: basic checks" 198 depends on DEBUG_KERNEL 199 help 200 Say Y here and build SMP to catch missing spinlock initialization 201 and certain other kinds of spinlock errors commonly made. This is 202 best used in conjunction with the NMI watchdog so that spinlock 203 deadlocks are also debuggable. 204 205config DEBUG_MUTEXES 206 bool "Mutex debugging: basic checks" 207 depends on DEBUG_KERNEL 208 help 209 This feature allows mutex semantics violations to be detected and 210 reported. 211 212config DEBUG_SEMAPHORE 213 bool "Semaphore debugging" 214 depends on DEBUG_KERNEL 215 depends on ALPHA || FRV 216 default n 217 help 218 If you say Y here then semaphore processing will issue lots of 219 verbose debugging messages. If you suspect a semaphore problem or a 220 kernel hacker asks for this option then say Y. Otherwise say N. 221 222config DEBUG_LOCK_ALLOC 223 bool "Lock debugging: detect incorrect freeing of live locks" 224 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 225 select DEBUG_SPINLOCK 226 select DEBUG_MUTEXES 227 select LOCKDEP 228 help 229 This feature will check whether any held lock (spinlock, rwlock, 230 mutex or rwsem) is incorrectly freed by the kernel, via any of the 231 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 232 vfree(), etc.), whether a live lock is incorrectly reinitialized via 233 spin_lock_init()/mutex_init()/etc., or whether there is any lock 234 held during task exit. 235 236config PROVE_LOCKING 237 bool "Lock debugging: prove locking correctness" 238 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 239 select LOCKDEP 240 select DEBUG_SPINLOCK 241 select DEBUG_MUTEXES 242 select DEBUG_LOCK_ALLOC 243 default n 244 help 245 This feature enables the kernel to prove that all locking 246 that occurs in the kernel runtime is mathematically 247 correct: that under no circumstance could an arbitrary (and 248 not yet triggered) combination of observed locking 249 sequences (on an arbitrary number of CPUs, running an 250 arbitrary number of tasks and interrupt contexts) cause a 251 deadlock. 252 253 In short, this feature enables the kernel to report locking 254 related deadlocks before they actually occur. 255 256 The proof does not depend on how hard and complex a 257 deadlock scenario would be to trigger: how many 258 participant CPUs, tasks and irq-contexts would be needed 259 for it to trigger. The proof also does not depend on 260 timing: if a race and a resulting deadlock is possible 261 theoretically (no matter how unlikely the race scenario 262 is), it will be proven so and will immediately be 263 reported by the kernel (once the event is observed that 264 makes the deadlock theoretically possible). 265 266 If a deadlock is impossible (i.e. the locking rules, as 267 observed by the kernel, are mathematically correct), the 268 kernel reports nothing. 269 270 NOTE: this feature can also be enabled for rwlocks, mutexes 271 and rwsems - in which case all dependencies between these 272 different locking variants are observed and mapped too, and 273 the proof of observed correctness is also maintained for an 274 arbitrary combination of these separate locking variants. 275 276 For more details, see Documentation/lockdep-design.txt. 277 278config LOCKDEP 279 bool 280 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 281 select STACKTRACE 282 select FRAME_POINTER if !X86 && !MIPS 283 select KALLSYMS 284 select KALLSYMS_ALL 285 286config LOCK_STAT 287 bool "Lock usage statistics" 288 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 289 select LOCKDEP 290 select DEBUG_SPINLOCK 291 select DEBUG_MUTEXES 292 select DEBUG_LOCK_ALLOC 293 default n 294 help 295 This feature enables tracking lock contention points 296 297 For more details, see Documentation/lockstat.txt 298 299config DEBUG_LOCKDEP 300 bool "Lock dependency engine debugging" 301 depends on DEBUG_KERNEL && LOCKDEP 302 help 303 If you say Y here, the lock dependency engine will do 304 additional runtime checks to debug itself, at the price 305 of more runtime overhead. 306 307config TRACE_IRQFLAGS 308 depends on DEBUG_KERNEL 309 bool 310 default y 311 depends on TRACE_IRQFLAGS_SUPPORT 312 depends on PROVE_LOCKING 313 314config DEBUG_SPINLOCK_SLEEP 315 bool "Spinlock debugging: sleep-inside-spinlock checking" 316 depends on DEBUG_KERNEL 317 help 318 If you say Y here, various routines which may sleep will become very 319 noisy if they are called with a spinlock held. 320 321config DEBUG_LOCKING_API_SELFTESTS 322 bool "Locking API boot-time self-tests" 323 depends on DEBUG_KERNEL 324 help 325 Say Y here if you want the kernel to run a short self-test during 326 bootup. The self-test checks whether common types of locking bugs 327 are detected by debugging mechanisms or not. (if you disable 328 lock debugging then those bugs wont be detected of course.) 329 The following locking APIs are covered: spinlocks, rwlocks, 330 mutexes and rwsems. 331 332config STACKTRACE 333 bool 334 depends on DEBUG_KERNEL 335 depends on STACKTRACE_SUPPORT 336 337config DEBUG_KOBJECT 338 bool "kobject debugging" 339 depends on DEBUG_KERNEL 340 help 341 If you say Y here, some extra kobject debugging messages will be sent 342 to the syslog. 343 344config DEBUG_HIGHMEM 345 bool "Highmem debugging" 346 depends on DEBUG_KERNEL && HIGHMEM 347 help 348 This options enables addition error checking for high memory systems. 349 Disable for production systems. 350 351config DEBUG_BUGVERBOSE 352 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 353 depends on BUG 354 depends on ARM || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG || BFIN 355 default !EMBEDDED 356 help 357 Say Y here to make BUG() panics output the file name and line number 358 of the BUG call as well as the EIP and oops trace. This aids 359 debugging but costs about 70-100K of memory. 360 361config DEBUG_INFO 362 bool "Compile the kernel with debug info" 363 depends on DEBUG_KERNEL 364 help 365 If you say Y here the resulting kernel image will include 366 debugging info resulting in a larger kernel image. 367 This adds debug symbols to the kernel and modules (gcc -g), and 368 is needed if you intend to use kernel crashdump or binary object 369 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 370 Say Y here only if you plan to debug the kernel. 371 372 If unsure, say N. 373 374config DEBUG_VM 375 bool "Debug VM" 376 depends on DEBUG_KERNEL 377 help 378 Enable this to turn on extended checks in the virtual-memory system 379 that may impact performance. 380 381 If unsure, say N. 382 383config DEBUG_LIST 384 bool "Debug linked list manipulation" 385 depends on DEBUG_KERNEL 386 help 387 Enable this to turn on extended checks in the linked-list 388 walking routines. 389 390 If unsure, say N. 391 392config FRAME_POINTER 393 bool "Compile the kernel with frame pointers" 394 depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH || BFIN) 395 default y if DEBUG_INFO && UML 396 help 397 If you say Y here the resulting kernel image will be slightly larger 398 and slower, but it might give very useful debugging information on 399 some architectures or if you use external debuggers. 400 If you don't debug the kernel, you can say N. 401 402config FORCED_INLINING 403 bool "Force gcc to inline functions marked 'inline'" 404 depends on DEBUG_KERNEL 405 default y 406 help 407 This option determines if the kernel forces gcc to inline the functions 408 developers have marked 'inline'. Doing so takes away freedom from gcc to 409 do what it thinks is best, which is desirable for the gcc 3.x series of 410 compilers. The gcc 4.x series have a rewritten inlining algorithm and 411 disabling this option will generate a smaller kernel there. Hopefully 412 this algorithm is so good that allowing gcc4 to make the decision can 413 become the default in the future, until then this option is there to 414 test gcc for this. 415 416config BOOT_PRINTK_DELAY 417 bool "Delay each boot printk message by N milliseconds" 418 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 419 help 420 This build option allows you to read kernel boot messages 421 by inserting a short delay after each one. The delay is 422 specified in milliseconds on the kernel command line, 423 using "boot_delay=N". 424 425 It is likely that you would also need to use "lpj=M" to preset 426 the "loops per jiffie" value. 427 See a previous boot log for the "lpj" value to use for your 428 system, and then set "lpj=M" before setting "boot_delay=N". 429 NOTE: Using this option may adversely affect SMP systems. 430 I.e., processors other than the first one may not boot up. 431 BOOT_PRINTK_DELAY also may cause DETECT_SOFTLOCKUP to detect 432 what it believes to be lockup conditions. 433 434config RCU_TORTURE_TEST 435 tristate "torture tests for RCU" 436 depends on DEBUG_KERNEL 437 depends on m 438 default n 439 help 440 This option provides a kernel module that runs torture tests 441 on the RCU infrastructure. The kernel module may be built 442 after the fact on the running kernel to be tested, if desired. 443 444 Say M if you want the RCU torture tests to build as a module. 445 Say N if you are unsure. 446 447config LKDTM 448 tristate "Linux Kernel Dump Test Tool Module" 449 depends on DEBUG_KERNEL 450 depends on KPROBES 451 default n 452 help 453 This module enables testing of the different dumping mechanisms by 454 inducing system failures at predefined crash points. 455 If you don't need it: say N 456 Choose M here to compile this code as a module. The module will be 457 called lkdtm. 458 459 Documentation on how to use the module can be found in 460 drivers/misc/lkdtm.c 461 462config FAULT_INJECTION 463 bool "Fault-injection framework" 464 depends on DEBUG_KERNEL 465 help 466 Provide fault-injection framework. 467 For more details, see Documentation/fault-injection/. 468 469config FAILSLAB 470 bool "Fault-injection capability for kmalloc" 471 depends on FAULT_INJECTION 472 help 473 Provide fault-injection capability for kmalloc. 474 475config FAIL_PAGE_ALLOC 476 bool "Fault-injection capabilitiy for alloc_pages()" 477 depends on FAULT_INJECTION 478 help 479 Provide fault-injection capability for alloc_pages(). 480 481config FAIL_MAKE_REQUEST 482 bool "Fault-injection capability for disk IO" 483 depends on FAULT_INJECTION 484 help 485 Provide fault-injection capability for disk IO. 486 487config FAULT_INJECTION_DEBUG_FS 488 bool "Debugfs entries for fault-injection capabilities" 489 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 490 help 491 Enable configuration of fault-injection capabilities via debugfs. 492 493config FAULT_INJECTION_STACKTRACE_FILTER 494 bool "stacktrace filter for fault-injection capabilities" 495 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 496 depends on !X86_64 497 select STACKTRACE 498 select FRAME_POINTER 499 help 500 Provide stacktrace filter for fault-injection capabilities 501