On Sat, Oct 14, 2017 at 04:36:51AM -0700, tip-bot for Ingo Molnar wrote:
> Commit-ID: b483cf3bc249d7af706390efa63d6671e80d1c09
> Gitweb:
> https://git.kernel.org/tip/b483cf3bc249d7af706390efa63d6671e80d1c09
> Author: Ingo Molnar <mi...@kernel.org>
> AuthorDate: Sat, 14 Oct 2017 09:26:59 +0200
> Committer: Ingo Molnar <mi...@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 <jo...@kernel.org>
> Debugged-by: Johan Hovold <jo...@kernel.org>
> Reported-by: Johan Hovold <jo...@kernel.org>
> Cc: Arnd Bergmann <a...@arndb.de>
> Cc: Byungchul Park <byungchul.p...@lge.com>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Tony Lindgren <t...@atomide.com>
> Cc: kernel-t...@lge.com
> Cc: linux-arm-ker...@lists.infradead.org
> Cc: linux...@kvack.org
> Cc: linux-o...@vger.kernel.org
> Link: http://lkml.kernel.org/r/20171014072659.f2yr6mhm5ha3e...@gmail.com
> Signed-off-by: Ingo Molnar <mi...@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
I agree with disabling crossrelease as default, becasue of regression,
as I originally did.
However, it's expected to spend more time once it's enabled. Is the
following acceptable?
----->8-----
>From d796b36bbed5783a22879d745e4d332bb02697a5 Mon Sep 17 00:00:00 2001
From: Byungchul Park <byungchul.p...@lge.com>
Date: Mon, 16 Oct 2017 10:54:20 +0900
Subject: [PATCH] lockdep: Diable LOCKDEP_CROSSRELEASE as default
Lockdep slowdeon has been reported becasue of LOCKDEP_CROSSRELEASE. The
feature needs more time to work, but it's not desirable as default. So
disable the Kconfig as default.
Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
---
lib/Kconfig.debug | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3db9167..fa45f78 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1138,8 +1138,6 @@ config PROVE_LOCKING
select DEBUG_MUTEXES
select DEBUG_RT_MUTEXES if RT_MUTEXES
select DEBUG_LOCK_ALLOC
- select LOCKDEP_CROSSRELEASE if BROKEN
- select LOCKDEP_COMPLETIONS if BROKEN
select TRACE_IRQFLAGS
default n
help
@@ -1210,7 +1208,9 @@ config LOCK_STAT
(CONFIG_LOCKDEP defines "acquire" and "release" events.)
config LOCKDEP_CROSSRELEASE
- bool
+ bool "Lock debugging: enable cross-locking checks in lockdep"
+ depends on PROVE_LOCKING
+ default n
help
This makes lockdep work for crosslock which is a lock allowed to
be released in a different context from the acquisition context.
@@ -1220,7 +1220,9 @@ config LOCKDEP_CROSSRELEASE
detector, lockdep.
config LOCKDEP_COMPLETIONS
- bool
+ bool "Lock debugging: allow completions to use deadlock detector"
+ depends on LOCKDEP_CROSSRELEASE
+ default n
help
A deadlock caused by wait_for_completion() and complete() can be
detected by lockdep using crossrelease feature.
--
1.9.1
