linux-kernel - [tip:locking/urgent] locking/lockdep: Disable cross-release features for now

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Date:   Sat, 14 Oct 2017 04:36:51 -0700
From:   tip-bot for Ingo Molnar <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org, tony@...mide.com, hpa@...or.com,
        torvalds@...ux-foundation.org, mingo@...nel.org,
        byungchul.park@....com, arnd@...db.de, johan@...nel.org
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@...nel.org>
AuthorDate: Sat, 14 Oct 2017 09:26:59 +0200
Committer:  Ingo Molnar <mingo@...nel.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@...nel.org>
Debugged-by: Johan Hovold <johan@...nel.org>
Reported-by: Johan Hovold <johan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Byungchul Park <byungchul.park@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Tony Lindgren <tony@...mide.com>
Cc: kernel-team@....com
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-mm@...ck.org
Cc: linux-omap@...r.kernel.org
Link: http://lkml.kernel.org/r/20171014072659.f2yr6mhm5ha3eou7@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.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