Messages in this thread | | | From | Boqun Feng <> | Subject | [RFC tip/locking v2 00/13] lockdep: Support deadlock detection for recursive read locks | Date | Wed, 6 Sep 2017 16:28:11 +0800 |
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Hi Ingo and Peter,
This is V2 for recursive read lock support in lockdep. I fix several bugs in V1 and also add irq inversion detection support for recursive read locks.
V1: https://marc.info/?l=linux-kernel&m=150393341825453
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 is based on current master branch of Linus' tree:
e7d0c41ecc2e ("Merge tag 'devprop-4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm")
, and I also put it at:
git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git arr-rfc-v2
The whole series consists of 13 patches:
1. Do a clean up on the return value of __bfs() and its friends.
2. 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.
3. Make lock state LOCK_*_READ stand for recursive read lock only and LOCK_* stand for write lock and non-recursive read lock.
4-5 Extend __bfs() to be able to traverse the stong dependency patchs after recursive read locks added into the graph.
6-8 Adjust check_redundant(), check_noncircular() and check_irq_usage() with recursive read locks into consideration.
9. Finally add recursive read locks into the dependency graph.
10-11 Adjust lock cache chain key generation with recursive read locks into consideration, and provide a test case.
12-13 Add more test cases.
I did pass all the lockdep selftest cases(including those I introduce), and now run it on one of my box, haven't shot my feet yet.
Test and comments are welcome!
Regards, Boqun
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