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
