[PATCH 3/3] lockdep: document MAX_LOCKDEP_CHAIN_HLOCKS calculation

[Carlos Llamas <cmllamas@google.com>]

Add a comment to document the magic number '5' used in the calculation
of MAX_LOCKDEP_CHAIN_HLOCKS. This number represents the estimated
average depth (number of locks held) of a lock chain. This definition
was added in commit 443cd507ce7f ("lockdep: add lock_class information
to lock_chain and output it").

Cc: Huang Ying <ying.huang@intel.com>
Cc: J. R. Okajima <hooanon05g@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
---
 kernel/locking/lockdep_internals.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index bbe9000260d0..2b429ed103a8 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -119,6 +119,7 @@ static const unsigned long LOCKF_USED_IN_IRQ_READ =
 
 #define MAX_LOCKDEP_CHAINS	(1UL << MAX_LOCKDEP_CHAINS_BITS)
 
+/* We estimate that a chain holds 5 locks on average. */
 #define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
 
 extern struct lock_chain lock_chains[];
-- 
2.46.0.rc2.264.g509ed76dc8-goog