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Do 'make oldconfig' and accept all the defaults for new config options - reboot into the kernel and if everything goes well it should boot up fine and you should have /proc/lockdep and /proc/lockdep_stats files. Typically if the lock validator finds some problem it will print out voluminous debug output that begins with "BUG: ..." and which syslog output can be used by kernel developers to figure out the precise locking scenario. What does the lock validator do? It "observes" and maps all locking rules as they occur dynamically (as triggered by the kernel's natural use of spinlocks, rwlocks, mutexes and rwsems). Whenever the lock validator subsystem detects a new locking scenario, it validates this new rule against the existing set of rules. If this new rule is consistent with the existing set of rules then the new rule is added transparently and the kernel continues as normal. If the new rule could create a deadlock scenario then this condition is printed out. When determining validity of locking, all possible "deadlock scenarios" are considered: assuming arbitrary number of CPUs, arbitrary irq context and task context constellations, running arbitrary combinations of all the existing locking scenarios. In a typical system this means millions of separate scenarios. This is why we call it a "locking correctness" validator - for all rules that are observed the lock validator proves it with mathematical certainty that a deadlock could not occur (assuming that the lock validator implementation itself is correct and its internal data structures are not corrupted by some other kernel subsystem). [see more details and conditionals of this statement in include/linux/lockdep.h and Documentation/lockdep-design.txt] Furthermore, this "all possible scenarios" property of the validator also enables the finding of complex, highly unlikely multi-CPU multi-context races via single single-context rules, increasing the likelyhood of finding bugs drastically. In practical terms: the lock validator already found a bug in the upstream kernel that could only occur on systems with 3 or more CPUs, and which needed 3 very unlikely code sequences to occur at once on the 3 CPUs. That bug was found and reported on a single-CPU system (!). So in essence a race will be found "piecemail-wise", triggering all the necessary components for the race, without having to reproduce the race scenario itself! In its short existence the lock validator found and reported many bugs before they actually caused a real deadlock. To further increase the efficiency of the validator, the mapping is not per "lock instance", but per "lock-class". For example, all struct inode objects in the kernel have inode->inotify_mutex. If there are 10,000 inodes cached, then there are 10,000 lock objects. But ->inotify_mutex is a single "lock type", and all locking activities that occur against ->inotify_mutex are "unified" into this single lock-class. The advantage of the lock-class approach is that all historical ->inotify_mutex uses are mapped into a single (and as narrow as possible) set of locking rules - regardless of how many different tasks or inode structures it took to build this set of rules. The set of rules persist during the lifetime of the kernel. To see the rough magnitude of checking that the lock validator does, here's a portion of /proc/lockdep_stats, fresh after bootup: lock-classes: 694 [max: 2048] direct dependencies: 1598 [max: 8192] indirect dependencies: 17896 all direct dependencies: 16206 dependency chains: 1910 [max: 8192] in-hardirq chains: 17 in-softirq chains: 105 in-process chains: 1065 stack-trace entries: 38761 [max: 131072] combined max dependencies:2033928hardirq-safe locks: 24 hardirq-unsafe locks: 176 softirq-safe locks: 53 softirq-unsafe locks: 137 irq-safe locks: 59 irq-unsafe locks: 176 The lock validator has observed 1598 actual single-thread locking patterns, and has validated all possible2033928distinct locking scenarios. More details about the design of the lock validator can be found in Documentation/lockdep-design.txt, which can also found at: http://redhat.com/~mingo/lockdep-patches/lockdep-design.txt [bunk@stusta.de: cleanups] Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
275 lines
9.4 KiB
Plaintext
275 lines
9.4 KiB
Plaintext
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config PRINTK_TIME
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bool "Show timing information on printks"
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help
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Selecting this option causes timing information to be
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included in printk output. This allows you to measure
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the interval between kernel operations, including bootup
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operations. This is useful for identifying long delays
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in kernel startup.
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config MAGIC_SYSRQ
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bool "Magic SysRq key"
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depends on !UML
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help
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If you say Y here, you will have some control over the system even
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if the system crashes for example during kernel debugging (e.g., you
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will be able to flush the buffer cache to disk, reboot the system
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immediately or dump some status information). This is accomplished
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by pressing various keys while holding SysRq (Alt+PrintScreen). It
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also works on a serial console (on PC hardware at least), if you
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send a BREAK and then within 5 seconds a command keypress. The
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keys are documented in <file:Documentation/sysrq.txt>. Don't say Y
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unless you really know what this hack does.
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config UNUSED_SYMBOLS
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bool "Enable unused/obsolete exported symbols"
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default y if X86
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help
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Unused but exported symbols make the kernel needlessly bigger. For
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that reason most of these unused exports will soon be removed. This
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option is provided temporarily to provide a transition period in case
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some external kernel module needs one of these symbols anyway. If you
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encounter such a case in your module, consider if you are actually
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using the right API. (rationale: since nobody in the kernel is using
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this in a module, there is a pretty good chance it's actually the
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wrong interface to use). If you really need the symbol, please send a
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mail to the linux kernel mailing list mentioning the symbol and why
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you really need it, and what the merge plan to the mainline kernel for
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your module is.
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config DEBUG_KERNEL
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bool "Kernel debugging"
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help
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Say Y here if you are developing drivers or trying to debug and
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identify kernel problems.
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config LOG_BUF_SHIFT
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int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL
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range 12 21
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default 17 if S390 || LOCKDEP
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default 16 if X86_NUMAQ || IA64
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default 15 if SMP
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default 14
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help
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Select kernel log buffer size as a power of 2.
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Defaults and Examples:
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17 => 128 KB for S/390
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16 => 64 KB for x86 NUMAQ or IA-64
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15 => 32 KB for SMP
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14 => 16 KB for uniprocessor
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13 => 8 KB
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12 => 4 KB
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config DETECT_SOFTLOCKUP
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bool "Detect Soft Lockups"
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depends on DEBUG_KERNEL
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default y
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help
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Say Y here to enable the kernel to detect "soft lockups",
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which are bugs that cause the kernel to loop in kernel
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mode for more than 10 seconds, without giving other tasks a
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chance to run.
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When a soft-lockup is detected, the kernel will print the
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current stack trace (which you should report), but the
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system will stay locked up. This feature has negligible
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overhead.
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(Note that "hard lockups" are separate type of bugs that
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can be detected via the NMI-watchdog, on platforms that
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support it.)
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config SCHEDSTATS
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bool "Collect scheduler statistics"
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depends on DEBUG_KERNEL && PROC_FS
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help
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If you say Y here, additional code will be inserted into the
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scheduler and related routines to collect statistics about
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scheduler behavior and provide them in /proc/schedstat. These
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stats may be useful for both tuning and debugging the scheduler
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If you aren't debugging the scheduler or trying to tune a specific
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application, you can say N to avoid the very slight overhead
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this adds.
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config DEBUG_SLAB
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bool "Debug slab memory allocations"
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depends on DEBUG_KERNEL && SLAB
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help
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Say Y here to have the kernel do limited verification on memory
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allocation as well as poisoning memory on free to catch use of freed
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memory. This can make kmalloc/kfree-intensive workloads much slower.
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config DEBUG_SLAB_LEAK
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bool "Memory leak debugging"
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depends on DEBUG_SLAB
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config DEBUG_PREEMPT
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bool "Debug preemptible kernel"
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depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
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default y
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help
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If you say Y here then the kernel will use a debug variant of the
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commonly used smp_processor_id() function and will print warnings
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if kernel code uses it in a preemption-unsafe way. Also, the kernel
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will detect preemption count underflows.
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config DEBUG_RT_MUTEXES
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bool "RT Mutex debugging, deadlock detection"
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depends on DEBUG_KERNEL && RT_MUTEXES
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help
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This allows rt mutex semantics violations and rt mutex related
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deadlocks (lockups) to be detected and reported automatically.
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config DEBUG_PI_LIST
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bool
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default y
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depends on DEBUG_RT_MUTEXES
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config RT_MUTEX_TESTER
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bool "Built-in scriptable tester for rt-mutexes"
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depends on DEBUG_KERNEL && RT_MUTEXES
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help
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This option enables a rt-mutex tester.
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config DEBUG_SPINLOCK
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bool "Spinlock debugging"
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depends on DEBUG_KERNEL
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help
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Say Y here and build SMP to catch missing spinlock initialization
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and certain other kinds of spinlock errors commonly made. This is
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best used in conjunction with the NMI watchdog so that spinlock
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deadlocks are also debuggable.
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config DEBUG_SPINLOCK_SLEEP
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bool "Sleep-inside-spinlock checking"
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depends on DEBUG_KERNEL
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help
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If you say Y here, various routines which may sleep will become very
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noisy if they are called with a spinlock held.
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config DEBUG_LOCKING_API_SELFTESTS
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bool "Locking API boot-time self-tests"
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depends on DEBUG_KERNEL
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help
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Say Y here if you want the kernel to run a short self-test during
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bootup. The self-test checks whether common types of locking bugs
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are detected by debugging mechanisms or not. (if you disable
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lock debugging then those bugs wont be detected of course.)
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The following locking APIs are covered: spinlocks, rwlocks,
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mutexes and rwsems.
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config STACKTRACE
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bool
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depends on STACKTRACE_SUPPORT
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config DEBUG_KOBJECT
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bool "kobject debugging"
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depends on DEBUG_KERNEL
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help
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If you say Y here, some extra kobject debugging messages will be sent
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to the syslog.
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config DEBUG_HIGHMEM
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bool "Highmem debugging"
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depends on DEBUG_KERNEL && HIGHMEM
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help
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This options enables addition error checking for high memory systems.
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Disable for production systems.
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config DEBUG_BUGVERBOSE
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bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EMBEDDED
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depends on BUG
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depends on ARM || ARM26 || M32R || M68K || SPARC32 || SPARC64 || X86_32 || FRV
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default !EMBEDDED
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help
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Say Y here to make BUG() panics output the file name and line number
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of the BUG call as well as the EIP and oops trace. This aids
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debugging but costs about 70-100K of memory.
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config DEBUG_INFO
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bool "Compile the kernel with debug info"
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depends on DEBUG_KERNEL
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help
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If you say Y here the resulting kernel image will include
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debugging info resulting in a larger kernel image.
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Say Y here only if you plan to debug the kernel.
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If unsure, say N.
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config DEBUG_FS
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bool "Debug Filesystem"
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depends on SYSFS
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help
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debugfs is a virtual file system that kernel developers use to put
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debugging files into. Enable this option to be able to read and
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write to these files.
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If unsure, say N.
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config DEBUG_VM
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bool "Debug VM"
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depends on DEBUG_KERNEL
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help
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Enable this to turn on extended checks in the virtual-memory system
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that may impact performance.
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If unsure, say N.
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config FRAME_POINTER
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bool "Compile the kernel with frame pointers"
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depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390)
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default y if DEBUG_INFO && UML
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help
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If you say Y here the resulting kernel image will be slightly larger
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and slower, but it might give very useful debugging information on
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some architectures or if you use external debuggers.
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If you don't debug the kernel, you can say N.
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config UNWIND_INFO
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bool "Compile the kernel with frame unwind information"
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depends on !IA64 && !PARISC
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depends on !MODULES || !(MIPS || PPC || SUPERH || V850)
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help
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If you say Y here the resulting kernel image will be slightly larger
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but not slower, and it will give very useful debugging information.
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If you don't debug the kernel, you can say N, but we may not be able
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to solve problems without frame unwind information or frame pointers.
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config STACK_UNWIND
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bool "Stack unwind support"
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depends on UNWIND_INFO
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depends on X86
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help
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This enables more precise stack traces, omitting all unrelated
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occurrences of pointers into kernel code from the dump.
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config FORCED_INLINING
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bool "Force gcc to inline functions marked 'inline'"
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depends on DEBUG_KERNEL
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default y
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help
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This option determines if the kernel forces gcc to inline the functions
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developers have marked 'inline'. Doing so takes away freedom from gcc to
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do what it thinks is best, which is desirable for the gcc 3.x series of
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compilers. The gcc 4.x series have a rewritten inlining algorithm and
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disabling this option will generate a smaller kernel there. Hopefully
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this algorithm is so good that allowing gcc4 to make the decision can
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become the default in the future, until then this option is there to
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test gcc for this.
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config RCU_TORTURE_TEST
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tristate "torture tests for RCU"
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depends on DEBUG_KERNEL
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default n
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help
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This option provides a kernel module that runs torture tests
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on the RCU infrastructure. The kernel module may be built
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after the fact on the running kernel to be tested, if desired.
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Say Y here if you want RCU torture tests to start automatically
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at boot time (you probably don't).
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Say M if you want the RCU torture tests to build as a module.
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Say N if you are unsure.
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