linux-kernel - [PATCH v2 1/2] config: Add new CONFIG_PROVE_LOCKING

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Date:   Mon, 26 Sep 2016 15:31:37 -0700
From:   Babu Moger <babu.moger@...cle.com>
To:     peterz@...radead.org, mingo@...hat.com, akpm@...ux-foundation.org,
        keescook@...omium.org, dan.j.williams@...el.com,
        aryabinin@...tuozzo.com, tj@...nel.org
Cc:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        babu.moger@...cle.com
Subject: [PATCH v2 1/2] config: Add new CONFIG_PROVE_LOCKING_SMALL

Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc.

This feature limits the space used for "Lock debugging: prove locking
correctness" by about 4MB. The current sparc systms have the limitation of
32MB size for kernel size including .text, .data and .bss sections. With
PROVE_LOCKING feature, the kernel size could grow beyond this limit and
causing system bootup issues. With this option, kernel limits the size
of the entries of lock_chains, stack_trace etc. so that kernel fits in
required size limit.  This is only visible for sparc.

Signed-off-by: Babu Moger <babu.moger@...cle.com>
---
 lib/Kconfig.debug |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b9cfdbf..c79de25 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1035,6 +1035,7 @@ config PROVE_LOCKING
 	select DEBUG_MUTEXES
 	select DEBUG_LOCK_ALLOC
 	select TRACE_IRQFLAGS
+	select PROVE_LOCKING_SMALL if SPARC
 	default n
 	help
 	 This feature enables the kernel to prove that all locking
@@ -1070,6 +1071,22 @@ config PROVE_LOCKING
 
 	 For more details, see Documentation/locking/lockdep-design.txt.
 
+config PROVE_LOCKING_SMALL
+	bool "Limit the space for prove locking correctness"
+	depends on PROVE_LOCKING && SPARC
+	help
+	 This feature limits the space used for "Lock debugging: prove
+	 locking correctness" by about 4MB. In sparc system, all the
+	 kernel's code, data, and bss, must have locked translations in
+	 the TLB so that it does not hit TLB misses. The current sparc
+	 chips have 8 TLB entries available that may be locked down, and
+	 with a 4mb page size, this gives a maximum of 32mb of memory for
+	 the kernel size. With PROVE_LOCKING feature, the kernel size could
+	 grow beyond this limit and causing system bootup issues. With
+	 this option, kernel limits the size of the entries of lock_chains,
+	 stack_trace etc. to debug PROVE_LOCKING so that kernel size fits
+	 in 32MB. This is only visible for SPARC.
+
 config LOCKDEP
 	bool
 	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
-- 
1.7.1