[PATCH v2 0/6] locking/lockdep: Reuse zapped chain_hlocks entries

Waiman Long
2019-12-16T15:15:48Z

v2:
- Revamp the chain_hlocks reuse patch to store the freed chain_hlocks
information in the chain_hlocks entries themselves avoiding the
need of a separate set of tracking structures. This, however,
requires a minimum allocation size of at least 2. Thanks to PeterZ
for his review and inspiring this change.
- Remove the leakage counter as it is no longer applicable.
- Add patch 6 to make the output of /proc/lockdep_chains more readable.

It was found that when running a workload that kept on adding lock
classes and then zapping them repetitively, the system will eventually
run out of chain_hlocks[] entries even though there were still plenty
of other lockdep data buffers available.

[ 4318.443670] BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!
[ 4318.444809] turning off the locking correctness validator.

In order to fix this problem, we have to make chain_hlocks[] entries
reusable just like other lockdep arrays. Besides that, the patchset
also adds some zapped class and chain_hlocks counters to be tracked by
/proc/lockdep_stats. It also fixes leakage in the irq context counters
and makes the output of /proc/lockdep_chains more readable.

Waiman Long (6):
locking/lockdep: Track number of zapped classes
locking/lockdep: Throw away all lock chains with zapped class
locking/lockdep: Track number of zapped lock chains
locking/lockdep: Reuse freed chain_hlocks entries
locking/lockdep: Decrement irq context counters when removing lock
chain
locking/lockdep: Display irq_context names in /proc/lockdep_chains

kernel/locking/lockdep.c | 307 +++++++++++++++++++++++------
kernel/locking/lockdep_internals.h | 14 +-
kernel/locking/lockdep_proc.c | 26 ++-
3 files changed, 282 insertions(+), 65 deletions(-)

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2.18.1