[PATCH v6 07/15] lockdep: Avoid adding redundant direct links of crosslocks

[Byungchul Park]

On my machine (QEMU x86_64, 4 core, mem 512M, enable-kvm), this patch
does not make different between before/after in lockdep_stats. So this
patch looks unnecessary. However, I wonder if it's still true in other
systems. Could anybody check lockdep_stats in your system?

Before (apply all crossrelease patches except this patch):

 lock-classes:                          988 [max: 8191]
 direct dependencies:                  5814 [max: 32768]
 indirect dependencies:               18915
 all direct dependencies:            119802
 dependency chains:                    6350 [max: 65536]
 dependency chain hlocks:             20771 [max: 327680]
 in-hardirq chains:                      52
 in-softirq chains:                     361
 in-process chains:                    5937
 stack-trace entries:                 80396 [max: 524288]
 combined max dependencies:       113926468
 hardirq-safe locks:                     42
 hardirq-unsafe locks:                  644
 softirq-safe locks:                    129
 softirq-unsafe locks:                  561
 irq-safe locks:                        135
 irq-unsafe locks:                      644
 hardirq-read-safe locks:                 2
 hardirq-read-unsafe locks:             127
 softirq-read-safe locks:                11
 softirq-read-unsafe locks:             119
 irq-read-safe locks:                    12
 irq-read-unsafe locks:                 127
 uncategorized locks:                   165
 unused locks:                            1
 max locking depth:                      14
 max bfs queue depth:                   168
 debug_locks:                             1

After (apply all crossrelease patches without exception):

 lock-classes:                          980 [max: 8191]
 direct dependencies:                  5604 [max: 32768]
 indirect dependencies:               18517
 all direct dependencies:            112620
 dependency chains:                    6215 [max: 65536]
 dependency chain hlocks:             20401 [max: 327680]
 in-hardirq chains:                      51
 in-softirq chains:                     298
 in-process chains:                    5866
 stack-trace entries:                 78707 [max: 524288]
 combined max dependencies:        91220116
 hardirq-safe locks:                     42
 hardirq-unsafe locks:                  637
 softirq-safe locks:                    117
 softirq-unsafe locks:                  561
 irq-safe locks:                        126
 irq-unsafe locks:                      637
 hardirq-read-safe locks:                 2
 hardirq-read-unsafe locks:             127
 softirq-read-safe locks:                10
 softirq-read-unsafe locks:             119
 irq-read-safe locks:                    11
 irq-read-unsafe locks:                 127
 uncategorized locks:                   165
 unused locks:                            1
 max locking depth:                      15
 max bfs queue depth:                   168
 debug_locks:                             1

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