lockdep: Support deadlock detection for recursive read locks in check_noncircular()

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Currently, lockdep only has limit support for deadlock detection for
recursive read locks.

This patch support deadlock detection for recursive read locks. The
basic idea is:

We are about to add dependency B -> A in to the dependency graph, we use
check_noncircular() to find whether we have a strong dependency path
A -> .. -> B so that we have a strong dependency circle (a closed strong
dependency path):

	 A -> .. -> B -> A

, which doesn't have two adjacent dependencies as -(*R)-> L -(S*)->.

Since A -> .. -> B is already a strong dependency path, so if either
B -> A is -(E*)-> or A -> .. -> B is -(*N)->, the circle A -> .. -> B ->
A is strong, otherwise not. So we introduce a new match function
hlock_conflict() to replace the class_equal() for the deadlock check in
check_noncircular().

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-10-boqun.feng@gmail.com

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Boqun Feng 2020-08-07 15:42:28 +08:00 • committed by Peter Zijlstra

parent 61775ed243

commit 9de0c9bbce

1 changed files with 35 additions and 8 deletions

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kernel/locking/lockdep.c

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