From: Boqun Feng <boqun.feng@gmail.com> To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, Andrea Parri <parri.andrea@gmail.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Boqun Feng <boqun.feng@gmail.com> Subject: [RFC tip/locking/lockdep v6 00/20] lockdep: Support deadlock detection for recursive read locks Date: Wed, 11 Apr 2018 21:50:50 +0800 [thread overview] Message-ID: <20180411135110.9217-1-boqun.feng@gmail.com> (raw) Hi Ingo and Peter, This is V6 for recursive read lock support in lockdep. I moved the explanation about reasoning to patch #1, which will help understand this whole series. This patchset is based on v4.16. Other changes since V5: * Rewrite the the explanation of the reasoning, focus on the proof of equivalence between closed strong paths and deadlock possiblity. * Rewrite the detection for irq-safe->irq-unsafe check, not only we support deadlock detection for recursive read locks, but also save two BFS searchs (one backwards and one forwards) in the detection. Thanks a lot for the discussion with Peter Zijlstra. * Annotate SRCU related primitives with 'check' lockdep annotations, so that we can detect deadlocks related to SRCU. Also a self test case is added. The use case is provided by Paul E. Mckenney. * Make __bfs(.math) return bool, as suggested by Peter Zijlstra. * Improve the readibliy of code based on good suggestions from Peter Zijlstra. Hope this time nobody's brain gets hurted ;-) * Minor fixes for typos. V1: https://marc.info/?l=linux-kernel&m=150393341825453 V2: https://marc.info/?l=linux-kernel&m=150468649417950 V3: https://marc.info/?l=linux-kernel&m=150637795424969 V4: https://marc.info/?l=linux-kernel&m=151550860121565 V5: https://marc.info/?l=linux-kernel&m=151928315529363 As Peter pointed out: https://marc.info/?l=linux-kernel&m=150349072023540 The lockdep current has a limit support for recursive read locks, the deadlock case as follow could not be detected: read_lock(A); lock(B); lock(B); write_lock(A); I got some inspiration from Gautham R Shenoy: https://lwn.net/Articles/332801/ , and came up with this series. The basic idea is: * Add recursive read locks into the graph * Classify dependencies into -(RR)->, -(NR)->, -(RN)->, -(NN)->, where R stands for recursive read lock, N stands for other locks(i.e. non-recursive read locks and write locks). * Define strong dependency paths as the paths of dependencies don't have two adjacent dependencies as -(*R)-> and -(R*)->. * Extend __bfs() to only traverse on strong dependency paths. * If __bfs() finds a strong dependency circle, then a deadlock is reported. The whole series consists of 20 patches: 1. Add documentation for recursive read lock deadlock detection reasoning 2. Do a clean up on the return value of __bfs() and its friends. 3. Make __bfs() able to visit every dependency until a match is found. The old version of __bfs() could only visit each lock class once, and this is insufficient if we are going to add recursive read locks into the dependency graph. 4. Redefine LOCK*_STATE*, now LOCK*_STATE_RR stand for recursive read lock only and LOCK*_STATE stand for write lock and non-recursive read lock. 5. Reduce the size of lock_list::distance. 6-7 Extend __bfs() to be able to traverse the stong dependency patchs after recursive read locks added into the graph. 8. Make __bfs(.math) return bool. 9-11 Adjust check_redundant(), check_noncircular() and check_irq_usage() with recursive read locks into consideration. 12. Finally add recursive read locks into the dependency graph. 13-14 Adjust lock cache chain key generation with recursive read locks into consideration, and provide a test case. 15-16 Add more test cases. 17. Revert commit d82fed752942 ("locking/lockdep/selftests: Fix mixed read-write ABBA tests"), 18. Add myself as a LOCKING PRIMITIVES reviewer. 19-20 Annotation SRCU correctly for deadlock detection, and provide a test case. This series passed all the lockdep selftest cases (including those I introduce). Test and comments are welcome! Regards, Boqun
next reply other threads:[~2018-04-11 13:47 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-11 13:50 Boqun Feng [this message] 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 01/20] lockdep/Documention: Recursive read lock detection reasoning Boqun Feng 2018-04-15 0:38 ` Randy Dunlap 2018-04-16 6:29 ` Boqun Feng 2018-04-27 13:50 ` Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 02/20] lockdep: Demagic the return value of BFS Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 03/20] lockdep: Make __bfs() visit every dependency until a match Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 04/20] lockdep: Redefine LOCK_*_STATE* bits Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 05/20] lockdep: Reduce the size of lock_list::distance Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 06/20] lockdep: Introduce lock_list::dep Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 07/20] lockdep: Extend __bfs() to work with multiple types of dependencies Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 08/20] lockdep: Make __bfs(.match) return bool Boqun Feng 2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 09/20] lockdep: Support deadlock detection for recursive read locks in check_noncircular() Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 10/20] lockdep: Adjust check_redundant() for recursive read change Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 11/20] lockdep: Fix recursive read lock related safe->unsafe detection Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 12/20] lockdep: Add recursive read locks into dependency graph Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 13/20] lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 14/20] lockdep: Take read/write status in consideration when generate chainkey Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 15/20] lockdep/selftest: Unleash irq_read_recursion2 and add more Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 16/20] lockdep/selftest: Add more recursive read related test cases Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 17/20] Revert "locking/lockdep/selftests: Fix mixed read-write ABBA tests" Boqun Feng 2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 18/20] MAINTAINERS: Add myself as a LOCKING PRIMITIVES reviewer Boqun Feng 2018-04-11 13:56 ` [RFC tip/locking/lockdep v6 19/20] rcu: Equip sleepable RCU with lockdep dependency graph checks Boqun Feng 2018-04-11 18:57 ` Paul E. McKenney 2018-04-12 2:12 ` Boqun Feng 2018-04-12 9:12 ` Peter Zijlstra 2018-04-13 13:24 ` Boqun Feng 2018-04-11 13:57 ` [RFC tip/locking/lockdep v6 20/20] lockdep/selftest: Add a test case for SRCU Boqun Feng
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