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_KERNEL 51 bool "Kernel debugging" 52 help 53 Say Y here if you are developing drivers or trying to debug and 54 identify kernel problems. 55 56config LOG_BUF_SHIFT 57 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL 58 range 12 21 59 default 17 if S390 || LOCKDEP 60 default 16 if X86_NUMAQ || IA64 61 default 15 if SMP 62 default 14 63 help 64 Select kernel log buffer size as a power of 2. 65 Defaults and Examples: 66 17 => 128 KB for S/390 67 16 => 64 KB for x86 NUMAQ or IA-64 68 15 => 32 KB for SMP 69 14 => 16 KB for uniprocessor 70 13 => 8 KB 71 12 => 4 KB 72 73config DETECT_SOFTLOCKUP 74 bool "Detect Soft Lockups" 75 depends on DEBUG_KERNEL && !S390 76 default y 77 help 78 Say Y here to enable the kernel to detect "soft lockups", 79 which are bugs that cause the kernel to loop in kernel 80 mode for more than 10 seconds, without giving other tasks a 81 chance to run. 82 83 When a soft-lockup is detected, the kernel will print the 84 current stack trace (which you should report), but the 85 system will stay locked up. This feature has negligible 86 overhead. 87 88 (Note that "hard lockups" are separate type of bugs that 89 can be detected via the NMI-watchdog, on platforms that 90 support it.) 91 92config SCHEDSTATS 93 bool "Collect scheduler statistics" 94 depends on DEBUG_KERNEL && PROC_FS 95 help 96 If you say Y here, additional code will be inserted into the 97 scheduler and related routines to collect statistics about 98 scheduler behavior and provide them in /proc/schedstat. These 99 stats may be useful for both tuning and debugging the scheduler 100 If you aren't debugging the scheduler or trying to tune a specific 101 application, you can say N to avoid the very slight overhead 102 this adds. 103 104config DEBUG_SLAB 105 bool "Debug slab memory allocations" 106 depends on DEBUG_KERNEL && SLAB 107 help 108 Say Y here to have the kernel do limited verification on memory 109 allocation as well as poisoning memory on free to catch use of freed 110 memory. This can make kmalloc/kfree-intensive workloads much slower. 111 112config DEBUG_SLAB_LEAK 113 bool "Memory leak debugging" 114 depends on DEBUG_SLAB 115 116config DEBUG_PREEMPT 117 bool "Debug preemptible kernel" 118 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 119 default y 120 help 121 If you say Y here then the kernel will use a debug variant of the 122 commonly used smp_processor_id() function and will print warnings 123 if kernel code uses it in a preemption-unsafe way. Also, the kernel 124 will detect preemption count underflows. 125 126config DEBUG_RT_MUTEXES 127 bool "RT Mutex debugging, deadlock detection" 128 depends on DEBUG_KERNEL && RT_MUTEXES 129 help 130 This allows rt mutex semantics violations and rt mutex related 131 deadlocks (lockups) to be detected and reported automatically. 132 133config DEBUG_PI_LIST 134 bool 135 default y 136 depends on DEBUG_RT_MUTEXES 137 138config RT_MUTEX_TESTER 139 bool "Built-in scriptable tester for rt-mutexes" 140 depends on DEBUG_KERNEL && RT_MUTEXES 141 help 142 This option enables a rt-mutex tester. 143 144config DEBUG_SPINLOCK 145 bool "Spinlock and rw-lock debugging: basic checks" 146 depends on DEBUG_KERNEL 147 help 148 Say Y here and build SMP to catch missing spinlock initialization 149 and certain other kinds of spinlock errors commonly made. This is 150 best used in conjunction with the NMI watchdog so that spinlock 151 deadlocks are also debuggable. 152 153config DEBUG_MUTEXES 154 bool "Mutex debugging: basic checks" 155 depends on DEBUG_KERNEL 156 help 157 This feature allows mutex semantics violations to be detected and 158 reported. 159 160config DEBUG_RWSEMS 161 bool "RW-sem debugging: basic checks" 162 depends on DEBUG_KERNEL 163 help 164 This feature allows read-write semaphore semantics violations to 165 be detected and reported. 166 167config DEBUG_LOCK_ALLOC 168 bool "Lock debugging: detect incorrect freeing of live locks" 169 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 170 select DEBUG_SPINLOCK 171 select DEBUG_MUTEXES 172 select DEBUG_RWSEMS 173 select LOCKDEP 174 help 175 This feature will check whether any held lock (spinlock, rwlock, 176 mutex or rwsem) is incorrectly freed by the kernel, via any of the 177 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 178 vfree(), etc.), whether a live lock is incorrectly reinitialized via 179 spin_lock_init()/mutex_init()/etc., or whether there is any lock 180 held during task exit. 181 182config PROVE_LOCKING 183 bool "Lock debugging: prove locking correctness" 184 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 185 select LOCKDEP 186 select DEBUG_SPINLOCK 187 select DEBUG_MUTEXES 188 select DEBUG_RWSEMS 189 select DEBUG_LOCK_ALLOC 190 default n 191 help 192 This feature enables the kernel to prove that all locking 193 that occurs in the kernel runtime is mathematically 194 correct: that under no circumstance could an arbitrary (and 195 not yet triggered) combination of observed locking 196 sequences (on an arbitrary number of CPUs, running an 197 arbitrary number of tasks and interrupt contexts) cause a 198 deadlock. 199 200 In short, this feature enables the kernel to report locking 201 related deadlocks before they actually occur. 202 203 The proof does not depend on how hard and complex a 204 deadlock scenario would be to trigger: how many 205 participant CPUs, tasks and irq-contexts would be needed 206 for it to trigger. The proof also does not depend on 207 timing: if a race and a resulting deadlock is possible 208 theoretically (no matter how unlikely the race scenario 209 is), it will be proven so and will immediately be 210 reported by the kernel (once the event is observed that 211 makes the deadlock theoretically possible). 212 213 If a deadlock is impossible (i.e. the locking rules, as 214 observed by the kernel, are mathematically correct), the 215 kernel reports nothing. 216 217 NOTE: this feature can also be enabled for rwlocks, mutexes 218 and rwsems - in which case all dependencies between these 219 different locking variants are observed and mapped too, and 220 the proof of observed correctness is also maintained for an 221 arbitrary combination of these separate locking variants. 222 223 For more details, see Documentation/lockdep-design.txt. 224 225config LOCKDEP 226 bool 227 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 228 select STACKTRACE 229 select FRAME_POINTER if !X86 230 select KALLSYMS 231 select KALLSYMS_ALL 232 233config DEBUG_LOCKDEP 234 bool "Lock dependency engine debugging" 235 depends on DEBUG_KERNEL && LOCKDEP 236 help 237 If you say Y here, the lock dependency engine will do 238 additional runtime checks to debug itself, at the price 239 of more runtime overhead. 240 241config TRACE_IRQFLAGS 242 depends on DEBUG_KERNEL 243 bool 244 default y 245 depends on TRACE_IRQFLAGS_SUPPORT 246 depends on PROVE_LOCKING 247 248config DEBUG_SPINLOCK_SLEEP 249 bool "Spinlock debugging: sleep-inside-spinlock checking" 250 depends on DEBUG_KERNEL 251 help 252 If you say Y here, various routines which may sleep will become very 253 noisy if they are called with a spinlock held. 254 255config DEBUG_LOCKING_API_SELFTESTS 256 bool "Locking API boot-time self-tests" 257 depends on DEBUG_KERNEL 258 help 259 Say Y here if you want the kernel to run a short self-test during 260 bootup. The self-test checks whether common types of locking bugs 261 are detected by debugging mechanisms or not. (if you disable 262 lock debugging then those bugs wont be detected of course.) 263 The following locking APIs are covered: spinlocks, rwlocks, 264 mutexes and rwsems. 265 266config STACKTRACE 267 bool 268 depends on DEBUG_KERNEL 269 depends on STACKTRACE_SUPPORT 270 271config DEBUG_KOBJECT 272 bool "kobject debugging" 273 depends on DEBUG_KERNEL 274 help 275 If you say Y here, some extra kobject debugging messages will be sent 276 to the syslog. 277 278config DEBUG_HIGHMEM 279 bool "Highmem debugging" 280 depends on DEBUG_KERNEL && HIGHMEM 281 help 282 This options enables addition error checking for high memory systems. 283 Disable for production systems. 284 285config DEBUG_BUGVERBOSE 286 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 287 depends on BUG 288 depends on ARM || ARM26 || AVR32 || M32R || M68K || SPARC32 || SPARC64 || FRV || SUPERH || GENERIC_BUG 289 default !EMBEDDED 290 help 291 Say Y here to make BUG() panics output the file name and line number 292 of the BUG call as well as the EIP and oops trace. This aids 293 debugging but costs about 70-100K of memory. 294 295config DEBUG_INFO 296 bool "Compile the kernel with debug info" 297 depends on DEBUG_KERNEL 298 help 299 If you say Y here the resulting kernel image will include 300 debugging info resulting in a larger kernel image. 301 Say Y here only if you plan to debug the kernel. 302 303 If unsure, say N. 304 305config DEBUG_FS 306 bool "Debug Filesystem" 307 depends on SYSFS 308 help 309 debugfs is a virtual file system that kernel developers use to put 310 debugging files into. Enable this option to be able to read and 311 write to these files. 312 313 If unsure, say N. 314 315config DEBUG_VM 316 bool "Debug VM" 317 depends on DEBUG_KERNEL 318 help 319 Enable this to turn on extended checks in the virtual-memory system 320 that may impact performance. 321 322 If unsure, say N. 323 324config DEBUG_LIST 325 bool "Debug linked list manipulation" 326 depends on DEBUG_KERNEL 327 help 328 Enable this to turn on extended checks in the linked-list 329 walking routines. 330 331 If unsure, say N. 332 333config FRAME_POINTER 334 bool "Compile the kernel with frame pointers" 335 depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || AVR32 || SUPERH) 336 default y if DEBUG_INFO && UML 337 help 338 If you say Y here the resulting kernel image will be slightly larger 339 and slower, but it might give very useful debugging information on 340 some architectures or if you use external debuggers. 341 If you don't debug the kernel, you can say N. 342 343config UNWIND_INFO 344 bool "Compile the kernel with frame unwind information" 345 depends on !IA64 && !PARISC && !ARM 346 depends on !MODULES || !(MIPS || PPC || SUPERH || V850) 347 help 348 If you say Y here the resulting kernel image will be slightly larger 349 but not slower, and it will give very useful debugging information. 350 If you don't debug the kernel, you can say N, but we may not be able 351 to solve problems without frame unwind information or frame pointers. 352 353config STACK_UNWIND 354 bool "Stack unwind support" 355 depends on UNWIND_INFO 356 depends on X86 357 help 358 This enables more precise stack traces, omitting all unrelated 359 occurrences of pointers into kernel code from the dump. 360 361config FORCED_INLINING 362 bool "Force gcc to inline functions marked 'inline'" 363 depends on DEBUG_KERNEL 364 default y 365 help 366 This option determines if the kernel forces gcc to inline the functions 367 developers have marked 'inline'. Doing so takes away freedom from gcc to 368 do what it thinks is best, which is desirable for the gcc 3.x series of 369 compilers. The gcc 4.x series have a rewritten inlining algorithm and 370 disabling this option will generate a smaller kernel there. Hopefully 371 this algorithm is so good that allowing gcc4 to make the decision can 372 become the default in the future, until then this option is there to 373 test gcc for this. 374 375config HEADERS_CHECK 376 bool "Run 'make headers_check' when building vmlinux" 377 depends on !UML 378 help 379 This option will extract the user-visible kernel headers whenever 380 building the kernel, and will run basic sanity checks on them to 381 ensure that exported files do not attempt to include files which 382 were not exported, etc. 383 384 If you're making modifications to header files which are 385 relevant for userspace, say 'Y', and check the headers 386 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 387 your build tree), to make sure they're suitable. 388 389config RCU_TORTURE_TEST 390 tristate "torture tests for RCU" 391 depends on DEBUG_KERNEL 392 default n 393 help 394 This option provides a kernel module that runs torture tests 395 on the RCU infrastructure. The kernel module may be built 396 after the fact on the running kernel to be tested, if desired. 397 398 Say Y here if you want RCU torture tests to start automatically 399 at boot time (you probably don't). 400 Say M if you want the RCU torture tests to build as a module. 401 Say N if you are unsure. 402 403config LKDTM 404 tristate "Linux Kernel Dump Test Tool Module" 405 depends on KPROBES 406 default n 407 help 408 This module enables testing of the different dumping mechanisms by 409 inducing system failures at predefined crash points. 410 If you don't need it: say N 411 Choose M here to compile this code as a module. The module will be 412 called lkdtm. 413 414 Documentation on how to use the module can be found in 415 drivers/misc/lkdtm.c 416