1 2config PRINTK_TIME 3 bool "Show timing information on printks" 4 help 5 Selecting this option causes timing information to be 6 included in printk output. This allows you to measure 7 the interval between kernel operations, including bootup 8 operations. This is useful for identifying long delays 9 in kernel startup. 10 11 12config MAGIC_SYSRQ 13 bool "Magic SysRq key" 14 depends on !UML 15 help 16 If you say Y here, you will have some control over the system even 17 if the system crashes for example during kernel debugging (e.g., you 18 will be able to flush the buffer cache to disk, reboot the system 19 immediately or dump some status information). This is accomplished 20 by pressing various keys while holding SysRq (Alt+PrintScreen). It 21 also works on a serial console (on PC hardware at least), if you 22 send a BREAK and then within 5 seconds a command keypress. The 23 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 24 unless you really know what this hack does. 25 26config UNUSED_SYMBOLS 27 bool "Enable unused/obsolete exported symbols" 28 default y if X86 29 help 30 Unused but exported symbols make the kernel needlessly bigger. For 31 that reason most of these unused exports will soon be removed. This 32 option is provided temporarily to provide a transition period in case 33 some external kernel module needs one of these symbols anyway. If you 34 encounter such a case in your module, consider if you are actually 35 using the right API. (rationale: since nobody in the kernel is using 36 this in a module, there is a pretty good chance it's actually the 37 wrong interface to use). If you really need the symbol, please send a 38 mail to the linux kernel mailing list mentioning the symbol and why 39 you really need it, and what the merge plan to the mainline kernel for 40 your module is. 41 42config DEBUG_KERNEL 43 bool "Kernel debugging" 44 help 45 Say Y here if you are developing drivers or trying to debug and 46 identify kernel problems. 47 48config LOG_BUF_SHIFT 49 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL 50 range 12 21 51 default 17 if S390 || LOCKDEP 52 default 16 if X86_NUMAQ || IA64 53 default 15 if SMP 54 default 14 55 help 56 Select kernel log buffer size as a power of 2. 57 Defaults and Examples: 58 17 => 128 KB for S/390 59 16 => 64 KB for x86 NUMAQ or IA-64 60 15 => 32 KB for SMP 61 14 => 16 KB for uniprocessor 62 13 => 8 KB 63 12 => 4 KB 64 65config DETECT_SOFTLOCKUP 66 bool "Detect Soft Lockups" 67 depends on DEBUG_KERNEL 68 default y 69 help 70 Say Y here to enable the kernel to detect "soft lockups", 71 which are bugs that cause the kernel to loop in kernel 72 mode for more than 10 seconds, without giving other tasks a 73 chance to run. 74 75 When a soft-lockup is detected, the kernel will print the 76 current stack trace (which you should report), but the 77 system will stay locked up. This feature has negligible 78 overhead. 79 80 (Note that "hard lockups" are separate type of bugs that 81 can be detected via the NMI-watchdog, on platforms that 82 support it.) 83 84config SCHEDSTATS 85 bool "Collect scheduler statistics" 86 depends on DEBUG_KERNEL && PROC_FS 87 help 88 If you say Y here, additional code will be inserted into the 89 scheduler and related routines to collect statistics about 90 scheduler behavior and provide them in /proc/schedstat. These 91 stats may be useful for both tuning and debugging the scheduler 92 If you aren't debugging the scheduler or trying to tune a specific 93 application, you can say N to avoid the very slight overhead 94 this adds. 95 96config DEBUG_SLAB 97 bool "Debug slab memory allocations" 98 depends on DEBUG_KERNEL && SLAB 99 help 100 Say Y here to have the kernel do limited verification on memory 101 allocation as well as poisoning memory on free to catch use of freed 102 memory. This can make kmalloc/kfree-intensive workloads much slower. 103 104config DEBUG_SLAB_LEAK 105 bool "Memory leak debugging" 106 depends on DEBUG_SLAB 107 108config DEBUG_PREEMPT 109 bool "Debug preemptible kernel" 110 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 111 default y 112 help 113 If you say Y here then the kernel will use a debug variant of the 114 commonly used smp_processor_id() function and will print warnings 115 if kernel code uses it in a preemption-unsafe way. Also, the kernel 116 will detect preemption count underflows. 117 118config DEBUG_RT_MUTEXES 119 bool "RT Mutex debugging, deadlock detection" 120 depends on DEBUG_KERNEL && RT_MUTEXES 121 help 122 This allows rt mutex semantics violations and rt mutex related 123 deadlocks (lockups) to be detected and reported automatically. 124 125config DEBUG_PI_LIST 126 bool 127 default y 128 depends on DEBUG_RT_MUTEXES 129 130config RT_MUTEX_TESTER 131 bool "Built-in scriptable tester for rt-mutexes" 132 depends on DEBUG_KERNEL && RT_MUTEXES 133 help 134 This option enables a rt-mutex tester. 135 136config DEBUG_SPINLOCK 137 bool "Spinlock and rw-lock debugging: basic checks" 138 depends on DEBUG_KERNEL 139 help 140 Say Y here and build SMP to catch missing spinlock initialization 141 and certain other kinds of spinlock errors commonly made. This is 142 best used in conjunction with the NMI watchdog so that spinlock 143 deadlocks are also debuggable. 144 145config DEBUG_MUTEXES 146 bool "Mutex debugging: basic checks" 147 depends on DEBUG_KERNEL 148 help 149 This feature allows mutex semantics violations to be detected and 150 reported. 151 152config DEBUG_RWSEMS 153 bool "RW-sem debugging: basic checks" 154 depends on DEBUG_KERNEL 155 help 156 This feature allows read-write semaphore semantics violations to 157 be detected and reported. 158 159config DEBUG_LOCK_ALLOC 160 bool "Lock debugging: detect incorrect freeing of live locks" 161 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 162 select DEBUG_SPINLOCK 163 select DEBUG_MUTEXES 164 select DEBUG_RWSEMS 165 select LOCKDEP 166 help 167 This feature will check whether any held lock (spinlock, rwlock, 168 mutex or rwsem) is incorrectly freed by the kernel, via any of the 169 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 170 vfree(), etc.), whether a live lock is incorrectly reinitialized via 171 spin_lock_init()/mutex_init()/etc., or whether there is any lock 172 held during task exit. 173 174config PROVE_LOCKING 175 bool "Lock debugging: prove locking correctness" 176 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 177 select LOCKDEP 178 select DEBUG_SPINLOCK 179 select DEBUG_MUTEXES 180 select DEBUG_RWSEMS 181 select DEBUG_LOCK_ALLOC 182 default n 183 help 184 This feature enables the kernel to prove that all locking 185 that occurs in the kernel runtime is mathematically 186 correct: that under no circumstance could an arbitrary (and 187 not yet triggered) combination of observed locking 188 sequences (on an arbitrary number of CPUs, running an 189 arbitrary number of tasks and interrupt contexts) cause a 190 deadlock. 191 192 In short, this feature enables the kernel to report locking 193 related deadlocks before they actually occur. 194 195 The proof does not depend on how hard and complex a 196 deadlock scenario would be to trigger: how many 197 participant CPUs, tasks and irq-contexts would be needed 198 for it to trigger. The proof also does not depend on 199 timing: if a race and a resulting deadlock is possible 200 theoretically (no matter how unlikely the race scenario 201 is), it will be proven so and will immediately be 202 reported by the kernel (once the event is observed that 203 makes the deadlock theoretically possible). 204 205 If a deadlock is impossible (i.e. the locking rules, as 206 observed by the kernel, are mathematically correct), the 207 kernel reports nothing. 208 209 NOTE: this feature can also be enabled for rwlocks, mutexes 210 and rwsems - in which case all dependencies between these 211 different locking variants are observed and mapped too, and 212 the proof of observed correctness is also maintained for an 213 arbitrary combination of these separate locking variants. 214 215 For more details, see Documentation/lockdep-design.txt. 216 217config LOCKDEP 218 bool 219 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 220 select STACKTRACE 221 select FRAME_POINTER 222 select KALLSYMS 223 select KALLSYMS_ALL 224 225config DEBUG_LOCKDEP 226 bool "Lock dependency engine debugging" 227 depends on DEBUG_KERNEL && LOCKDEP 228 help 229 If you say Y here, the lock dependency engine will do 230 additional runtime checks to debug itself, at the price 231 of more runtime overhead. 232 233config TRACE_IRQFLAGS 234 depends on DEBUG_KERNEL 235 bool 236 default y 237 depends on TRACE_IRQFLAGS_SUPPORT 238 depends on PROVE_LOCKING 239 240config DEBUG_SPINLOCK_SLEEP 241 bool "Spinlock debugging: sleep-inside-spinlock checking" 242 depends on DEBUG_KERNEL 243 help 244 If you say Y here, various routines which may sleep will become very 245 noisy if they are called with a spinlock held. 246 247config DEBUG_LOCKING_API_SELFTESTS 248 bool "Locking API boot-time self-tests" 249 depends on DEBUG_KERNEL 250 help 251 Say Y here if you want the kernel to run a short self-test during 252 bootup. The self-test checks whether common types of locking bugs 253 are detected by debugging mechanisms or not. (if you disable 254 lock debugging then those bugs wont be detected of course.) 255 The following locking APIs are covered: spinlocks, rwlocks, 256 mutexes and rwsems. 257 258config STACKTRACE 259 bool 260 depends on DEBUG_KERNEL 261 depends on STACKTRACE_SUPPORT 262 263config DEBUG_KOBJECT 264 bool "kobject debugging" 265 depends on DEBUG_KERNEL 266 help 267 If you say Y here, some extra kobject debugging messages will be sent 268 to the syslog. 269 270config DEBUG_HIGHMEM 271 bool "Highmem debugging" 272 depends on DEBUG_KERNEL && HIGHMEM 273 help 274 This options enables addition error checking for high memory systems. 275 Disable for production systems. 276 277config DEBUG_BUGVERBOSE 278 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED 279 depends on BUG 280 depends on ARM || ARM26 || M32R || M68K || SPARC32 || SPARC64 || X86_32 || FRV 281 default !EMBEDDED 282 help 283 Say Y here to make BUG() panics output the file name and line number 284 of the BUG call as well as the EIP and oops trace. This aids 285 debugging but costs about 70-100K of memory. 286 287config DEBUG_INFO 288 bool "Compile the kernel with debug info" 289 depends on DEBUG_KERNEL 290 help 291 If you say Y here the resulting kernel image will include 292 debugging info resulting in a larger kernel image. 293 Say Y here only if you plan to debug the kernel. 294 295 If unsure, say N. 296 297config DEBUG_FS 298 bool "Debug Filesystem" 299 depends on SYSFS 300 help 301 debugfs is a virtual file system that kernel developers use to put 302 debugging files into. Enable this option to be able to read and 303 write to these files. 304 305 If unsure, say N. 306 307config DEBUG_VM 308 bool "Debug VM" 309 depends on DEBUG_KERNEL 310 help 311 Enable this to turn on extended checks in the virtual-memory system 312 that may impact performance. 313 314 If unsure, say N. 315 316config FRAME_POINTER 317 bool "Compile the kernel with frame pointers" 318 depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390) 319 default y if DEBUG_INFO && UML 320 help 321 If you say Y here the resulting kernel image will be slightly larger 322 and slower, but it might give very useful debugging information on 323 some architectures or if you use external debuggers. 324 If you don't debug the kernel, you can say N. 325 326config UNWIND_INFO 327 bool "Compile the kernel with frame unwind information" 328 depends on !IA64 && !PARISC 329 depends on !MODULES || !(MIPS || PPC || SUPERH || V850) 330 help 331 If you say Y here the resulting kernel image will be slightly larger 332 but not slower, and it will give very useful debugging information. 333 If you don't debug the kernel, you can say N, but we may not be able 334 to solve problems without frame unwind information or frame pointers. 335 336config STACK_UNWIND 337 bool "Stack unwind support" 338 depends on UNWIND_INFO 339 depends on X86 340 help 341 This enables more precise stack traces, omitting all unrelated 342 occurrences of pointers into kernel code from the dump. 343 344config FORCED_INLINING 345 bool "Force gcc to inline functions marked 'inline'" 346 depends on DEBUG_KERNEL 347 default y 348 help 349 This option determines if the kernel forces gcc to inline the functions 350 developers have marked 'inline'. Doing so takes away freedom from gcc to 351 do what it thinks is best, which is desirable for the gcc 3.x series of 352 compilers. The gcc 4.x series have a rewritten inlining algorithm and 353 disabling this option will generate a smaller kernel there. Hopefully 354 this algorithm is so good that allowing gcc4 to make the decision can 355 become the default in the future, until then this option is there to 356 test gcc for this. 357 358config RCU_TORTURE_TEST 359 tristate "torture tests for RCU" 360 depends on DEBUG_KERNEL 361 default n 362 help 363 This option provides a kernel module that runs torture tests 364 on the RCU infrastructure. The kernel module may be built 365 after the fact on the running kernel to be tested, if desired. 366 367 Say Y here if you want RCU torture tests to start automatically 368 at boot time (you probably don't). 369 Say M if you want the RCU torture tests to build as a module. 370 Say N if you are unsure. 371