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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