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Subject[tip:locking/urgent] locking/lockdep: Disable cross-release features for now
Commit-ID:  b483cf3bc249d7af706390efa63d6671e80d1c09
Gitweb: https://git.kernel.org/tip/b483cf3bc249d7af706390efa63d6671e80d1c09
Author: Ingo Molnar <mingo@kernel.org>
AuthorDate: Sat, 14 Oct 2017 09:26:59 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 14 Oct 2017 12:50:26 +0200

locking/lockdep: Disable cross-release features for now

Johan Hovold reported a big lockdep slowdown on his system, caused by lockdep:

> I had noticed that the BeagleBone Black boot time appeared to have
> increased significantly with 4.14 and yesterday I finally had time to
> investigate it.
>
> Boot time (from "Linux version" to login prompt) had in fact doubled
> since 4.13 where it took 17 seconds (with my current config) compared to
> the 35 seconds I now see with 4.14-rc4.
>
> I quick bisect pointed to lockdep and specifically the following commit:
>
> 28a903f63ec0 ("locking/lockdep: Handle non(or multi)-acquisition of a crosslock")

Because the final v4.14 release is close, disable the cross-release lockdep
features for now.

Bisected-by: Johan Hovold <johan@kernel.org>
Debugged-by: Johan Hovold <johan@kernel.org>
Reported-by: Johan Hovold <johan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Lindgren <tony@atomide.com>
Cc: kernel-team@lge.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mm@kvack.org
Cc: linux-omap@vger.kernel.org
Link: http://lkml.kernel.org/r/20171014072659.f2yr6mhm5ha3eou7@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
lib/Kconfig.debug | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2689b7c..e270584 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1092,8 +1092,8 @@ config PROVE_LOCKING
select DEBUG_MUTEXES
select DEBUG_RT_MUTEXES if RT_MUTEXES
select DEBUG_LOCK_ALLOC
- select LOCKDEP_CROSSRELEASE
- select LOCKDEP_COMPLETIONS
+ select LOCKDEP_CROSSRELEASE if BROKEN
+ select LOCKDEP_COMPLETIONS if BROKEN
select TRACE_IRQFLAGS
default n
help
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