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2012-02-21lockdep: Add CPU-idle/offline warning to lockdep-RCU splatPaul E. McKenney1-1/+7
It is illegal to use RCU from a CPU that has reported idleness or offlinedness to RCU. However, it can be quite difficult to determine from a stack trace whether or not a given CPU is idle or offline. Therefore, this commit adds idle/offline diagnostics to the lockdep-RCU error message. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-01-06Merge branch 'perf-core-for-linus' of ↵Linus Torvalds1-17/+13
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (106 commits) perf kvm: Fix copy & paste error in description perf script: Kill script_spec__delete perf top: Fix a memory leak perf stat: Introduce get_ratio_color() helper perf session: Remove impossible condition check perf tools: Fix feature-bits rework fallout, remove unused variable perf script: Add generic perl handler to process events perf tools: Use for_each_set_bit() to iterate over feature flags perf tools: Unify handling of features when writing feature section perf report: Accept fifos as input file perf tools: Moving code in some files perf tools: Fix out-of-bound access to struct perf_session perf tools: Continue processing header on unknown features perf tools: Improve macros for struct feature_ops perf: builtin-record: Document and check that mmap_pages must be a power of two. perf: builtin-record: Provide advice if mmap'ing fails with EPERM. perf tools: Fix truncated annotation perf script: look up thread using tid instead of pid perf tools: Look up thread names for system wide profiling perf tools: Fix comm for processes with named threads ...
2012-01-06Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds1-0/+22
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits) cpu: Export cpu_up() rcu: Apply ACCESS_ONCE() to rcu_boost() return value Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" docs: Additional LWN links to RCU API rcu: Augment rcu_batch_end tracing for idle and callback state rcu: Add rcutorture tests for srcu_read_lock_raw() rcu: Make rcutorture test for hotpluggability before offlining CPUs driver-core/cpu: Expose hotpluggability to the rest of the kernel rcu: Remove redundant rcu_cpu_stall_suppress declaration rcu: Adaptive dyntick-idle preparation rcu: Keep invoking callbacks if CPU otherwise idle rcu: Irq nesting is always 0 on rcu_enter_idle_common rcu: Don't check irq nesting from rcu idle entry/exit rcu: Permit dyntick-idle with callbacks pending rcu: Document same-context read-side constraints rcu: Identify dyntick-idle CPUs on first force_quiescent_state() pass rcu: Remove dynticks false positives and RCU failures rcu: Reduce latency of rcu_prepare_for_idle() rcu: Eliminate RCU_FAST_NO_HZ grace-period hang rcu: Avoid needlessly IPIing CPUs at GP end ...
2011-12-20Merge commit 'v3.2-rc6' into perf/coreIngo Molnar1-1/+7
Merge reason: Update with the latest fixes. Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-11rcu: Inform the user about extended quiescent state on PROVE_RCU warningFrederic Weisbecker1-0/+22
Inform the user if an RCU usage error is detected by lockdep while in an extended quiescent state (in this case, the RCU-free window in idle). This is accomplished by adding a line to the RCU lockdep splat indicating whether or not the splat occurred in extended quiescent state. Uses of RCU from within extended quiescent state mode are totally ignored by RCU, hence the importance of this diagnostic. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2011-12-06lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()Yong Zhang1-1/+7
Since commit f59de89 ("lockdep: Clear whole lockdep_map on initialization"), lockdep_init_map() will clear all the struct. But it will break lock_set_class()/lock_set_subclass(). A typical race condition is like below: CPU A CPU B lock_set_subclass(lockA); lock_set_class(lockA); lockdep_init_map(lockA); /* lockA->name is cleared */ memset(lockA); __lock_acquire(lockA); /* lockA->class_cache[] is cleared */ register_lock_class(lockA); look_up_lock_class(lockA); WARN_ON_ONCE(class->name != lock->name); lock->name = name; So restore to what we have done before commit f59de89 but annotate ->lock with kmemcheck_mark_initialized() to suppress the kmemcheck warning reported in commit f59de89. Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reported-by: Borislav Petkov <bp@alien8.de> Suggested-by: Vegard Nossum <vegard.nossum@gmail.com> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: <stable@kernel.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111109080451.GB8124@zhy Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06lockdep: Print lock name in lockdep_init_error()Ming Lei1-1/+4
This patch prints the name of the lock which is acquired before lockdep_init() is called, so that users can easily find which lock triggered the lockdep init error warning. This patch also removes the lockdep_init_error() message of "Arch code didn't call lockdep_init() early enough?" since lockdep_init() is called in arch independent code now. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1321508072-23853-2-git-send-email-tom.leiming@gmail.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06lockdep, kmemcheck: Annotate ->lock in lockdep_init_map()Yong Zhang1-1/+7
Since commit f59de89 ("lockdep: Clear whole lockdep_map on initialization"), lockdep_init_map() will clear all the struct. But it will break lock_set_class()/lock_set_subclass(). A typical race condition is like below: CPU A CPU B lock_set_subclass(lockA); lock_set_class(lockA); lockdep_init_map(lockA); /* lockA->name is cleared */ memset(lockA); __lock_acquire(lockA); /* lockA->class_cache[] is cleared */ register_lock_class(lockA); look_up_lock_class(lockA); WARN_ON_ONCE(class->name != lock->name); lock->name = name; So restore to what we have done before commit f59de89 but annotate ->lock with kmemcheck_mark_initialized() to suppress the kmemcheck warning reported in commit f59de89. Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reported-by: Borislav Petkov <bp@alien8.de> Suggested-by: Vegard Nossum <vegard.nossum@gmail.com> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111109080451.GB8124@zhy Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06lockdep, rtmutex, bug: Show taint flags on errorBen Hutchings1-8/+15
Show the taint flags in all lockdep and rtmutex-debug error messages. Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1319773015.6759.30.camel@deadeye Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-11-14lockdep: Always try to set ->class_cache in register_lock_class() ↵Yong Zhang1-1/+2
lockdep_init_map() Commit ["62016250 lockdep: Add improved subclass caching"] tries to improve performance (expecially to reduce the cost of rq->lock) when using lockdep, but it fails due to lockdep_init_map() in which ->class_cache is cleared. The typical caller is lock_set_subclass(), after that class will not be cached anymore. This patch tries to achive the goal of commit 62016250 by always setting ->class_cache in register_lock_class(). === Score comparison of benchmarks === for i in `seq 1 10`; do ./perf bench -f simple sched messaging; done before: min: 0.604, max: 0.660, avg: 0.622 after: min: 0.414, max: 0.473, avg: 0.427 for i in `seq 1 10`; do ./perf bench -f simple sched messaging -g 40; done before: min: 2.347, max: 2.421, avg: 2.391 after: min: 1.652, max: 1.699, avg: 1.671 Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111109080714.GC8124@zhy Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-11-11Merge branch 'tip/perf/core' of ↵Ingo Molnar1-17/+13
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into perf/core
2011-11-07lockdep: Show subclass in pretty print of lockdep outputSteven Rostedt1-17/+13
The pretty print of the lockdep debug splat uses just the lock name to show how the locking scenario happens. But when it comes to nesting locks, the output becomes confusing which takes away the point of the pretty printing of the lock scenario. Without displaying the subclass info, we get the following output: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(slock-AF_INET); lock(slock-AF_INET); lock(slock-AF_INET); lock(slock-AF_INET); *** DEADLOCK *** The above looks more of a A->A locking bug than a A->B B->A. By adding the subclass to the output, we can see what really happened: other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(slock-AF_INET); lock(slock-AF_INET/1); lock(slock-AF_INET); lock(slock-AF_INET/1); *** DEADLOCK *** This bug was discovered while tracking down a real bug caught by lockdep. Link: http://lkml.kernel.org/r/20111025202049.GB25043@hostway.ca Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Reported-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Simon Kirby <sim@hostway.ca> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-10-26Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds1-37/+47
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits) rcu: Move propagation of ->completed from rcu_start_gp() to rcu_report_qs_rsp() rcu: Remove rcu_needs_cpu_flush() to avoid false quiescent states rcu: Wire up RCU_BOOST_PRIO for rcutree rcu: Make rcu_torture_boost() exit loops at end of test rcu: Make rcu_torture_fqs() exit loops at end of test rcu: Permit rt_mutex_unlock() with irqs disabled rcu: Avoid having just-onlined CPU resched itself when RCU is idle rcu: Suppress NMI backtraces when stall ends before dump rcu: Prohibit grace periods during early boot rcu: Simplify unboosting checks rcu: Prevent early boot set_need_resched() from __rcu_pending() rcu: Dump local stack if cannot dump all CPUs' stacks rcu: Move __rcu_read_unlock()'s barrier() within if-statement rcu: Improve rcu_assign_pointer() and RCU_INIT_POINTER() documentation rcu: Make rcu_assign_pointer() unconditionally insert a memory barrier rcu: Make rcu_implicit_dynticks_qs() locals be correct size rcu: Eliminate in_irq() checks in rcu_enter_nohz() nohz: Remove nohz_cpu_mask rcu: Document interpretation of RCU-lockdep splats rcu: Allow rcutorture's stat_interval parameter to be changed at runtime ...
2011-09-29rcu: Restore checks for blocking in RCU read-side critical sectionsPaul E. McKenney1-37/+47
Long ago, using TREE_RCU with PREEMPT would result in "scheduling while atomic" diagnostics if you blocked in an RCU read-side critical section. However, PREEMPT now implies TREE_PREEMPT_RCU, which defeats this diagnostic. This commit therefore adds a replacement diagnostic based on PROVE_RCU. Because rcu_lockdep_assert() and lockdep_rcu_dereference() are now being used for things that have nothing to do with rcu_dereference(), rename lockdep_rcu_dereference() to lockdep_rcu_suspicious() and add a third argument that is a string indicating what is suspicious. This third argument is passed in from a new third argument to rcu_lockdep_assert(). Update all calls to rcu_lockdep_assert() to add an informative third argument. Also, add a pair of rcu_lockdep_assert() calls from within rcu_note_context_switch(), one complaining if a context switch occurs in an RCU-bh read-side critical section and another complaining if a context switch occurs in an RCU-sched read-side critical section. These are present only if the PROVE_RCU kernel parameter is enabled. Finally, fix some checkpatch whitespace complaints in lockdep.c. Again, you must enable PROVE_RCU to see these new diagnostics. But you are enabling PROVE_RCU to check out new RCU uses in any case, aren't you? Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-09-18lockdep: Comment all warningsPeter Zijlstra1-9/+147
Andrew requested I comment all the lockdep WARN()s to help other people figure out wth is wrong.. Requested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1315301493.3191.9.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-08-09lockdep: Fix wrong assumption in match_held_lockPeter Zijlstra1-1/+7
match_held_lock() was assuming it was being called on a lock class that had already seen usage. This condition was true for bug-free code using lockdep_assert_held(), since you're in fact holding the lock when calling it. However the assumption fails the moment you assume the assertion can fail, which is the whole point of having the assertion in the first place. Anyway, now that there's more lockdep_is_held() users, notably __rcu_dereference_check(), its much easier to trigger this since we test for a number of locks and we only need to hold any one of them to be good. Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1312547787.28695.2.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-08-04lockdep: Clear whole lockdep_map on initializationTejun Heo1-4/+1
lockdep_init_map() only initializes parts of lockdep_map and triggers kmemcheck warning when it is copied as a whole. There isn't anything to be gained by clearing selectively. memset() the whole structure and remove loop for ->class_cache[] clearing. Addresses https://bugzilla.kernel.org/show_bug.cgi?id=35532 Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Christian Casteyde <casteyde.christian@free.fr> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=35532 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20110714131909.GJ3455@htj.dyndns.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-08-04lockdep: Fix up warningPeter Zijlstra1-1/+1
On Sun, 2011-07-24 at 21:06 -0400, Arnaud Lacombe wrote: > /src/linux/linux/kernel/lockdep.c: In function 'mark_held_locks': > /src/linux/linux/kernel/lockdep.c:2471:31: warning: comparison of > distinct pointer types lacks a cast The warning is harmless in this case, but the below makes it go away. Reported-by: Arnaud Lacombe <lacombar@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1311588599.2617.56.camel@laptop Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-08-04lockdep: Fix trace_hardirqs_on_caller()Peter Zijlstra1-14/+16
Commit dd4e5d3ac4a ("lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion") made a bit of a mess of the various checks and error conditions. In particular it moved the check for !irqs_disabled() before the spurious enable test, resulting in some warnings. Reported-by: Arnaud Lacombe <lacombar@gmail.com> Reported-by: Dave Jones <davej@redhat.com> Reported-and-tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1311679697.24752.28.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-07-23Merge branch 'core-printk-for-linus' of ↵Linus Torvalds1-10/+20
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion printk: Fix console_sem vs logbuf_lock unlock race printk: Release console_sem after logbuf_lock
2011-07-21lockdep: Fix lockdep_no_validate against IRQ statesPeter Zijlstra1-0/+3
Thomas noticed that a lock marked with lockdep_set_novalidate_class() will still trigger warnings for IRQ inversions. Cure this by skipping those when marking irq state. Reported-and-tested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/n/tip-2dp5vmpsxeraqm42kgww6ge2@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-06-22lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursionPeter Zijlstra1-10/+20
Commit: 1efc5da3cf56: [PATCH] order of lockdep off/on in vprintk() should be changed explains the reason for having raw_local_irq_*() and lockdep_off() in printk(). Instead of working around the broken recursion detection of interrupt state tracking, fix it. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: efault@gmx.de Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110621153806.185242734@chello.nl Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-06-07lockdep: Fix lock_is_held() on recursionPeter Zijlstra1-1/+1
The main lock_is_held() user is lockdep_assert_held(), avoid false assertions in lockdep_off() sections by unconditionally reporting the lock is taken. [ the reason this is important is a lockdep_assert_held() in ttwu() which triggers a warning under lockdep_off() as in printk() which can trigger another wakeup and lock up due to spinlock recursion, as reported and heroically debugged by Arne Jansen ] Reported-and-tested-by: Arne Jansen <lists@die-jansens.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: <stable@kernel.org> Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Remove cmpxchg to update nr_chain_hlocksSteven Rostedt1-10/+4
For some reason nr_chain_hlocks is updated with cmpxchg, but this is performed inside of the lockdep global "grab_lock()", which also makes simple modification of this variable atomic. Remove the cmpxchg logic for updating nr_chain_hlocks and simplify the code. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014300.727863282@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Print a nicer description for simple irq lock inversionsSteven Rostedt1-0/+20
Lockdep output can be pretty cryptic, having nicer output can save a lot of head scratching. When a simple irq inversion scenario is detected by lockdep (lock A taken in interrupt context but also in thread context without disabling interrupts) we now get the following (hopefully more informative) output: other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(lockA); <Interrupt> lock(lockA); *** DEADLOCK *** Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014300.436140880@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Replace "Bad BFS generated tree" message with something less crypticSteven Rostedt1-1/+1
The message of "Bad BFS generated tree" is a bit confusing. Replace it with a more sane error message. Thanks to Peter Zijlstra for helping me come up with a better message. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014300.135521252@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Print a nicer description for irq inversion bugsSteven Rostedt1-5/+29
Irq inversion and irq dependency bugs are only subtly different. The diffenerence lies where the interrupt occurred. For irq dependency: irq_disable lock(A) lock(B) unlock(B) unlock(A) irq_enable lock(B) unlock(B) <interrupt> lock(A) The interrupt comes in after it has been established that lock A can be held when taking an irq unsafe lock. Lockdep detects the problem when taking lock A in interrupt context. With the irq_inversion the irq happens before it is established and lockdep detects the problem with the taking of lock B: <interrupt> lock(A) irq_disable lock(A) lock(B) unlock(B) unlock(A) irq_enable lock(B) unlock(B) Since the problem with the locking logic for both of these issues is in actuality the same, they both should report the same scenario. This patch implements that and prints this: other info that might help us debug this: Chain exists of: &rq->lock --> lockA --> lockC Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(lockC); local_irq_disable(); lock(&rq->lock); lock(lockA); <Interrupt> lock(&rq->lock); *** DEADLOCK *** Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014259.910720381@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Print a nicer description for simple deadlocksSteven Rostedt1-0/+21
Lockdep output can be pretty cryptic, having nicer output can save a lot of head scratching. When a simple deadlock scenario is detected by lockdep (lock A -> lock A) we now get the following new output: other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(lock)->rlock); lock(&(lock)->rlock); *** DEADLOCK *** Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014259.643930104@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Print a nicer description for normal deadlocksSteven Rostedt1-0/+55
The lockdep output can be pretty cryptic, having nicer output can save a lot of head scratching. When a normal deadlock scenario is detected by lockdep (lock A -> lock B and there exists a place where lock B -> lock A) we now get the following new output: other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(lockB); lock(lockA); lock(lockB); lock(lockA); *** DEADLOCK *** On cases where there's a deeper chair, it shows the partial chain that can cause the issue: Chain exists of: lockC --> lockA --> lockB Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(lockB); lock(lockA); lock(lockB); lock(lockC); *** DEADLOCK *** Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014259.380621789@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-04-22lockdep: Print a nicer description for irq lock inversionsSteven Rostedt1-0/+70
Locking order inversion due to interrupts is a subtle problem. When an irq lockiinversion discovered by lockdep it currently reports something like: [ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ] ... and then prints out the locks that are involved, as back traces. Judging by lkml feedback developers were routinely confused by what a HARDIRQ->safe to unsafe issue is all about, and sometimes even blew it off as a bug in lockdep. It is not obvious when lockdep prints this message about a lock that is never taken in interrupt context. After explaining the problems that lockdep is reporting, I decided to add a description of the problem in visual form. Now the following is shown: --- other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(lockA); local_irq_disable(); lock(&rq->lock); lock(lockA); <Interrupt> lock(&rq->lock); *** DEADLOCK *** --- The above is the case when the unsafe lock is taken while holding a lock taken in irq context. But when a lock is taken that also grabs a unsafe lock, the call chain is shown: --- other info that might help us debug this: Chain exists of: &rq->lock --> lockA --> lockC Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(lockC); local_irq_disable(); lock(&rq->lock); lock(lockA); <Interrupt> lock(&rq->lock); *** DEADLOCK *** Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110421014259.132728798@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-03-31Fix common misspellingsLucas De Marchi1-2/+2
Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
2011-01-20lockdep: Move early boot local IRQ enable/disable status to init/main.cTejun Heo1-17/+1
During early boot, local IRQ is disabled until IRQ subsystem is properly initialized. During this time, no one should enable local IRQ and some operations which usually are not allowed with IRQ disabled, e.g. operations which might sleep or require communications with other processors, are allowed. lockdep tracked this with early_boot_irqs_off/on() callbacks. As other subsystems need this information too, move it to init/main.c and make it generally available. While at it, toggle the boolean to early_boot_irqs_disabled instead of enabled so that it can be initialized with %false and %true indicates the exceptional condition. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Pekka Enberg <penberg@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> LKML-Reference: <20110120110635.GB6036@htj.dyndns.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18lockdep: Check the depth of subclassHitoshi Mitake1-8/+10
Current look_up_lock_class() doesn't check the parameter "subclass". This rarely rises problems because the main caller of this function, register_lock_class(), checks it. But register_lock_class() is not the only function which calls look_up_lock_class(). lock_set_class() and its callees also call it. And lock_set_class() doesn't check this parameter. This will rise problems when the the value of subclass is larger than MAX_LOCKDEP_SUBCLASSES. Because the address (used as the key of class) caliculated with too large subclass has a probability to point another key in different lock_class_key. Of course this problem depends on the memory layout and occurs with really low probability. Signed-off-by: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Dmitry Torokhov <dtor@mail.ru> Cc: Vojtech Pavlik <vojtech@ucw.cz> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1286958626-986-1-git-send-email-mitake@dcl.info.waseda.ac.jp> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-10-18lockdep: Add improved subclass cachingHitoshi Mitake1-7/+18
Current lockdep_map only caches one class with subclass == 0, and looks up hash table of classes when subclass != 0. It seems that this has no problem because the case of subclass != 0 is rare. But locks of struct rq are acquired with subclass == 1 when task migration is executed. Task migration is high frequent event, so I modified lockdep to cache subclasses. I measured the score of perf bench sched messaging. This patch has slightly but certain (order of milli seconds or 10 milli seconds) effect when lots of tasks are running. I'll show the result in the tail of this description. NR_LOCKDEP_CACHING_CLASSES specifies how many classes can be cached in the instances of lockdep_map. I discussed with Peter Zijlstra in LinuxCon Japan about this approach and he taught me that caching every subclasses(8) is cleary waste of memory. So number of cached classes should be configurable. === Score comparison of benchmarks === # "min" means best score, and "max" means worst score for i in `seq 1 10`; do ./perf bench -f simple sched messaging; done before: min: 0.565000, max: 0.583000, avg: 0.572500 after: min: 0.559000, max: 0.568000, avg: 0.563300 # with more processes for i in `seq 1 10`; do ./perf bench -f simple sched messaging -g 40; done before: min: 2.274000, max: 2.298000, avg: 2.286300 after: min: 2.242000, max: 2.270000, avg: 2.259700 Signed-off-by: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1286269311-28336-2-git-send-email-mitake@dcl.info.waseda.ac.jp> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-08-17lockdep: Remove __debug_show_held_locksJohn Kacur1-7/+1
There is no longer any functional difference between __debug_show_held_locks() and debug_show_held_locks(), so remove the former. Signed-off-by: John Kacur <jkacur@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1281021054-4228-1-git-send-email-jkacur@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-06-09sched_clock: Add local_clock() API and improve documentationPeter Zijlstra1-1/+1
For people who otherwise get to write: cpu_clock(smp_processor_id()), there is now: local_clock(). Also, as per suggestion from Andrew, provide some documentation on the various clock interfaces, and minimize the unsigned long long vs u64 mess. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jens Axboe <jaxboe@fusionio.com> LKML-Reference: <1275052414.1645.52.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-05-21lockdep: Add novalidate class for dev->mutex conversionPeter Zijlstra1-0/+5
The conversion of device->sem to device->mutex resulted in lockdep warnings. Create a novalidate class for now until the driver folks come up with separate classes. That way we have at least the basic mutex debugging coverage. Add a checkpatch error so the usage is reserved for device->mutex. [ tglx: checkpatch and compile fix for LOCKDEP=n ] Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-05-18Merge branch 'perf-core-for-linus' of ↵Linus Torvalds1-2/+2
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (311 commits) perf tools: Add mode to build without newt support perf symbols: symbol inconsistency message should be done only at verbose=1 perf tui: Add explicit -lslang option perf options: Type check all the remaining OPT_ variants perf options: Type check OPT_BOOLEAN and fix the offenders perf options: Check v type in OPT_U?INTEGER perf options: Introduce OPT_UINTEGER perf tui: Add workaround for slang < 2.1.4 perf record: Fix bug mismatch with -c option definition perf options: Introduce OPT_U64 perf tui: Add help window to show key associations perf tui: Make <- exit menus too perf newt: Add single key shortcuts for zoom into DSO and threads perf newt: Exit browser unconditionally when CTRL+C, q or Q is pressed perf newt: Fix the 'A'/'a' shortcut for annotate perf newt: Make <- exit the ui_browser x86, perf: P4 PMU - fix counters management logic perf newt: Make <- zoom out filters perf report: Report number of events, not samples perf hist: Clarify events_stats fields usage ... Fix up trivial conflicts in kernel/fork.c and tools/perf/builtin-record.c
2010-05-18Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds1-0/+3
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (24 commits) rcu: remove all rcu head initializations, except on_stack initializations rcu head introduce rcu head init on stack Debugobjects transition check rcu: fix build bug in RCU_FAST_NO_HZ builds rcu: RCU_FAST_NO_HZ must check RCU dyntick state rcu: make SRCU usable in modules rcu: improve the RCU CPU-stall warning documentation rcu: reduce the number of spurious RCU_SOFTIRQ invocations rcu: permit discontiguous cpu_possible_mask CPU numbering rcu: improve RCU CPU stall-warning messages rcu: print boot-time console messages if RCU configs out of ordinary rcu: disable CPU stall warnings upon panic rcu: enable CPU_STALL_VERBOSE by default rcu: slim down rcutiny by removing rcu_scheduler_active and friends rcu: refactor RCU's context-switch handling rcu: rename rcutiny rcu_ctrlblk to rcu_sched_ctrlblk rcu: shrink rcutiny by making synchronize_rcu_bh() be inline rcu: fix now-bogus rcu_scheduler_active comments. rcu: Fix bogus CONFIG_PROVE_LOCKING in comments to reflect reality. rcu: ignore offline CPUs in last non-dyntick-idle CPU check ...
2010-05-10rcu: optionally leave lockdep enabled after RCU lockdep splatLai Jiangshan1-0/+3
There is no need to disable lockdep after an RCU lockdep splat, so remove the debug_lockdeps_off() from lockdep_rcu_dereference(). To avoid repeated lockdep splats, use a static variable in the inlined rcu_dereference_check() and rcu_dereference_protected() macros so that a given instance splats only once, but so that multiple instances can be detected per boot. This is controlled by a new config variable CONFIG_PROVE_RCU_REPEATEDLY, which is disabled by default. This provides the normal lockdep behavior by default, but permits people who want to find multiple RCU-lockdep splats per boot to easily do so. Requested-by: Eric Paris <eparis@redhat.com> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Tested-by: Eric Paris <eparis@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2010-05-09tracing: Drop the nested field from lock_release eventFrederic Weisbecker1-1/+1
Drop the nested field as we don't use it. Every nested state can be computed from a state machine on post processing already. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Steven Rostedt <rostedt@goodmis.org>
2010-05-09tracing: Drop lock_acquired waittime fieldFrederic Weisbecker1-1/+1
Drop the waittime field from the lock_acquired event, we can calculate it by substracting the lock_acquired event timestamp with the matching lock_acquire one. It is not needed and takes useless space in the traces. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Steven Rostedt <rostedt@goodmis.org>
2010-05-07lockdep: Reduce stack_trace usageYong Zhang1-8/+21
When calling check_prevs_add(), if all validations passed add_lock_to_list() will add new lock to dependency tree and alloc stack_trace for each list_entry. But at this time, we are always on the same stack, so stack_trace for each list_entry has the same value. This is redundant and eats up lots of memory which could lead to warning on low MAX_STACK_TRACE_ENTRIES. Use one copy of stack_trace instead. V2: As suggested by Peter Zijlstra, move save_trace() from check_prevs_add() to check_prev_add(). Add tracking for trylock dependence which is also redundant. Signed-off-by: Yong Zhang <yong.zhang0@windriver.com> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20100504065711.GC10784@windriver.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-05-04lockdep: Provide off case for redundant_hardirqs_on incrementFrederic Weisbecker1-1/+1
We forgot to provide a !CONFIG_DEBUG_LOCKDEP case for the redundant_hardirqs_on stat handling. Manage that in the headers with a new __debug_atomic_inc() helper. Fixes: kernel/lockdep.c:2306: error: 'lockdep_stats' undeclared (first use in this function) kernel/lockdep.c:2306: error: (Each undeclared identifier is reported only once kernel/lockdep.c:2306: error: for each function it appears in.) Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org>
2010-04-30lockdep: Fix redundant_hardirqs_on incremented with irqs enabledFrederic Weisbecker1-1/+6
When a path restore the flags while irqs are already enabled, we update the per cpu var redundant_hardirqs_on in a racy fashion and debug_atomic_inc() warns about this situation. In this particular case, loosing a few hits in a stat is not a big deal, so increment it without protection. v2: Don't bother with disabling irq, we can miss one count in rare situations Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: David Miller <davem@davemloft.net> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2010-04-30Merge commit 'v2.6.34-rc6' into core/lockingFrederic Weisbecker1-22/+10
Merge reason: Further lockdep patches depend on per cpu updates made in -rc1.
2010-04-06lockstat: Make lockstat counting per cpuFrederic Weisbecker1-30/+17
Locking statistics are implemented using global atomic variables. This is usually fine unless some path write them very often. This is the case for the function and function graph tracers that disable irqs for each entry saved (except if the function tracer is in preempt disabled only mode). And calls to local_irq_save/restore() increment hardirqs_on_events and hardirqs_off_events stats (or similar stats for redundant versions). Incrementing these global vars for each function ends up in too much cache bouncing if lockstats are enabled. To solve this, implement the debug_atomic_*() operations using per cpu vars. -v2: Use per_cpu() instead of get_cpu_var() to fetch the desired cpu vars on debug_atomic_read() -v3: Store the stats in a structure. No need for local_t as we are NMI/irq safe. -v4: Fix tons of build errors. I thought I had tested it but I probably forgot to select the relevant config. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <1270505417-8144-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Steven Rostedt <rostedt@goodmis.org>
2010-04-05Merge branch 'slabh' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/miscLinus Torvalds1-0/+1
* 'slabh' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc: eeepc-wmi: include slab.h staging/otus: include slab.h from usbdrv.h percpu: don't implicitly include slab.h from percpu.h kmemcheck: Fix build errors due to missing slab.h include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h iwlwifi: don't include iwl-dev.h from iwl-devtrace.h x86: don't include slab.h from arch/x86/include/asm/pgtable_32.h Fix up trivial conflicts in include/linux/percpu.h due to is_kernel_percpu_address() having been introduced since the slab.h cleanup with the percpu_up.c splitup.
2010-03-30include cleanup: Update gfp.h and slab.h includes to prepare for breaking ↵Tejun Heo1-0/+1
implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-29percpu, module: implement and use is_kernel/module_percpu_address()Tejun Heo1-16/+5
lockdep has custom code to check whether a pointer belongs to static percpu area which is somewhat broken. Implement proper is_kernel/module_percpu_address() and replace the custom code. On UP, percpu variables are regular static variables and can't be distinguished from them. Always return %false on UP. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@redhat.com>
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