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path: root/include/linux/lockdep.h
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2007-10-19workqueue: debug flushing deadlocks with lockdepJohannes Berg
In the following scenario: code path 1: my_function() -> lock(L1); ...; flush_workqueue(); ... code path 2: run_workqueue() -> my_work() -> ...; lock(L1); ... you can get a deadlock when my_work() is queued or running but my_function() has acquired L1 already. This patch adds a pseudo-lock to each workqueue to make lockdep warn about this scenario. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Acked-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-11lockdep: annotate rcu_read_{,un}lock{,_bh}Peter Zijlstra
lockdep annotate rcu_read_{,un}lock{,_bh} in order to catch imbalanced usage. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2007-10-11lockdep: syscall exit checkPeter Zijlstra
Provide a check to validate that we do not hold any locks when switching back to user-space. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-07-19lockstat: measure lock bouncingPeter Zijlstra
__acquire | lock _____ | \ | __contended | | | wait | _______/ |/ | __acquired | __release | unlock We measure acquisition and contention bouncing. This is done by recording a cpu stamp in each lock instance. Contention bouncing requires the cpu stamp to be set on acquisition. Hence we move __acquired into the generic path. __acquired is then used to measure acquisition bouncing by comparing the current cpu with the old stamp before replacing it. __contended is used to measure contention bouncing (only useful for preemptable locks) [akpm@linux-foundation.org: cleanups] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19lockdep: various fixesPeter Zijlstra
- update the copyright notices - use the default hash function - fix a thinko in a BUILD_BUG_ON - add a WARN_ON to spot inconsitent naming - fix a termination issue in /proc/lock_stat [akpm@linux-foundation.org: cleanups] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-19lockstat: core infrastructurePeter Zijlstra
Introduce the core lock statistics code. Lock statistics provides lock wait-time and hold-time (as well as the count of corresponding contention and acquisitions events). Also, the first few call-sites that encounter contention are tracked. Lock wait-time is the time spent waiting on the lock. This provides insight into the locking scheme, that is, a heavily contended lock is indicative of a too coarse locking scheme. Lock hold-time is the duration the lock was held, this provides a reference for the wait-time numbers, so they can be put into perspective. 1) lock 2) ... do stuff .. unlock 3) The time between 1 and 2 is the wait-time. The time between 2 and 3 is the hold-time. The lockdep held-lock tracking code is reused, because it already collects locks into meaningful groups (classes), and because it is an existing infrastructure for lock instrumentation. Currently lockdep tracks lock acquisition with two hooks: lock() lock_acquire() _lock() ... code protected by lock ... unlock() lock_release() _unlock() We need to extend this with two more hooks, in order to measure contention. lock_contended() - used to measure contention events lock_acquired() - completion of the contention These are then placed the following way: lock() lock_acquire() if (!_try_lock()) lock_contended() _lock() lock_acquired() ... do locked stuff ... unlock() lock_release() _unlock() (Note: the try_lock() 'trick' is used to avoid instrumenting all platform dependent lock primitive implementations.) It is also possible to toggle the two lockdep features at runtime using: /proc/sys/kernel/prove_locking /proc/sys/kernel/lock_stat (esp. turning off the O(n^2) prove_locking functionaliy can help) [akpm@linux-foundation.org: build fixes] [akpm@linux-foundation.org: nuke unneeded ifdefs] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-03-22[PATCH] lockdep: lockdep_depth vs. debug_locksJarek Poplawski
lockdep found a bug during a run of workqueue function - this could be also caused by a bug from other code running simultaneously. lockdep really shouldn't be used when debug_locks == 0! Reported-by: Folkert van Heusden <folkert@vanheusden.com> Inspired-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Jarek Poplawski <jarkao2@o2.pl> Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-12[PATCH] lockdep: forward declare struct task_structHeiko Carstens
3117df0453828bd045c16244e6f50e5714667a8a causes this: In file included from arch/s390/kernel/early.c:13: include/linux/lockdep.h:300: warning: "struct task_struct" declared inside parameter list include/linux/lockdep.h:300: warning: its scope is only this definition or declaration, which is probably not what you want Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-11[PATCH] lockdep: add graph depth information to /proc/lockdepJason Baron
Generate locking graph information into /proc/lockdep, for lock hierarchy documentation and visualization purposes. sample output: c089fd5c OPS: 138 FD: 14 BD: 1 --..: &tty->termios_mutex -> [c07a3430] tty_ldisc_lock -> [c07a37f0] &port_lock_key -> [c07afdc0] &rq->rq_lock_key#2 The lock classes listed are all the first-hop lock dependencies that lockdep has seen so far. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2006-12-13[PATCH] lockdep: print irq-trace info on assertsIngo Molnar
When we print an assert due to scheduling-in-atomic bugs, and if lockdep is enabled, then the IRQ tracing information of lockdep can be printed to pinpoint the code location that disabled interrupts. This saved me quite a bit of debugging time in cases where the backtrace did not identify the irq-disabling site well enough. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07[PATCH] remove kernel/lockdep.c:lockdep_internalAdrian Bunk
Remove the no longer used lockdep_internal(). Signed-off-by: Adrian Bunk <bunk@stusta.de> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07[PATCH] debug: workqueue locking sanityPeter Zijlstra
Workqueue functions should not leak locks, assert so, printing the last function ran. Use macros in lockdep.h to avoid include dependency pains. [akpm@osdl.org: build fix] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-11Lockdep: fix compile error in drivers/input/serio/serio.cAndrew Morton
lockdep_set_subclass() was missing in !LOCKDEP case Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
2006-10-11Lockdep: add lockdep_set_class_and_subclass() and lockdep_set_subclass()Peter Zijlstra
This annotation makes it possible to assign a subclass on lock init. This annotation is meant to reduce the _nested() annotations by assigning a default subclass. One could do without this annotation and rely on lockdep_set_class() exclusively, but that would require a manual stack of struct lock_class_key objects. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
2006-09-29[PATCH] lockdep: don't pull in includes when lockdep disabledMichael S. Tsirkin
Do not pull in various includes through lockdep.h if lockdep is disabled. Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il> Cc: Ingo Molnar <mingo@elte.hu> Cc: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-10[PATCH] lockdep: core, reduce per-lock class-cache sizeIngo Molnar
lockdep_map is embedded into every lock, which blows up data structure sizes all around the kernel. Reduce the class-cache to be for the default class only - that is used in 99.9% of the cases and even if we dont have a class cached, the lookup in the class-hash is lockless. This change reduces the per-lock dep_map overhead by 56 bytes on 64-bit platforms and by 28 bytes on 32-bit platforms. Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-03[PATCH] lockdep: annotate genirqIngo Molnar
Teach special (recursive) locking code to the lock validator. Has no effect on non-lockdep kernels. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-07-03[PATCH] lockdep: coreIngo Molnar
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: 2033928 hardirq-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 possible 2033928 distinct 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>