linux-kernel - [PATCH 0/2] locking/lockdep: Track number of zapped classes & report abuse

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Date:   Thu, 29 Nov 2018 17:41:35 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Waiman Long <longman@...hat.com>
Subject: [PATCH 0/2] locking/lockdep: Track number of zapped classes & report abuse

When a kernel module is repeatedly load and unload, it will eventually
exhaust the lockdep entries resulting in a bug message. This is a use
case that the current lockdep code cannot support.

This patchset tracks the number of zapped classes and print a warning if
too many lockdep entries are wasted because of too many module unloading.
For example,

[ 2490.651531] BUG: MAX_LOCKDEP_KEYS too low!
[ 2490.669925] turning off the locking correctness validator.
[ 2490.669925] Please attach the output of /proc/lock_stat to the bug report
[ 2490.669926] ========================================================
[ 2490.669927] WARNING: 6499 out of 8191 locks have been destroyed
[ 2490.669927] through kernel module unload operations.
[ 2490.669928] The corresponding lockdep entries are not reusable.
[ 2490.669928] The system might have run out of lockdep entries because
[ 2490.669929] of repeated kernel module load and unload operations.
[ 2490.669929] Lockdep cannot support this particular use case.
[ 2490.669930] --------------------------------------------------------

Waiman Long (2):
  locking/lockdep: Annotate #else/#endif's that are far from #if
  locking/lockdep: Track number of zapped classes & report abuse

 kernel/locking/lockdep.c           | 42 ++++++++++++++++++++++++++++++--------
 kernel/locking/lockdep_internals.h |  1 +
 kernel/locking/lockdep_proc.c      |  2 ++
 3 files changed, 37 insertions(+), 8 deletions(-)

-- 
1.8.3.1