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Message-ID: <alpine.LFD.2.00.1004161727000.11320@localhost.localdomain>
Date: Fri, 16 Apr 2010 17:29:05 +0200 (CEST)
From: John Kacur <jkacur@...hat.com>
To: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc: linux-rt-users@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
Clark Williams <williams@...hat.com>,
"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC: PATCH v2] lockdep: Make MAX_STACK_TRACE_ENTRIES
configurable.
On Fri, 16 Apr 2010, John Kacur wrote:
>
> This patch was created against v2.6.33.2-rt13 but is also intended for
> mainline.
>
> Certain debug configurations tend to go over the MAX_STACK_TRACE_ENTRIES
> limit without there really being any problem.
>
> This patch keeps the old default, but allows the user to configure a
> higher value if desired.
>
> I tend to bump this value up for real-time debug configurations for
> example. This is preferrable to indiscriminately turning off the locking
> correctness validator.
>
> There have been some attempts to increase the default value in the past,
> that were met with resistance by some, because of the legitimate concern
> that this was growing too large and that we need to understand why. By
> making it configurable, I hope to satisfy both sets of people - those who
> believe they need to set it larger under special circumstances, and those
> who want a reasonably small default.
>
> From 57479e7620d312353f5f5b173742e011896a9c74 Mon Sep 17 00:00:00 2001
> From: John Kacur <jkacur@...hat.com>
> Date: Fri, 16 Apr 2010 13:24:02 +0200
> Subject: [RFC: PATCH] lockdep: Make MAX_STACK_TRACE_ENTRIES configurable.
>
> Certain configurations that have LOCKDEP turned on, run into the limit
> where the MAX_STACK_TRACE_ENTRIES are too small. Rather than simply
> turning of the locking correctness validator let the user configure this
> value to something reasonable for their system.
>
> Signed-off-by: John Kacur <jkacur@...hat.com>
> ---
> kernel/lockdep.c | 8 ++++----
> kernel/lockdep_internals.h | 6 ------
> lib/Kconfig.debug | 9 +++++++++
> 3 files changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> index 1199bda..6030521 100644
> --- a/kernel/lockdep.c
> +++ b/kernel/lockdep.c
> @@ -368,12 +368,12 @@ static int verbose(struct lock_class *class)
> * addresses. Protected by the graph_lock.
> */
> unsigned long nr_stack_trace_entries;
> -static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
> +static unsigned long stack_trace[CONFIG_MAX_STACK_TRACE_ENTRIES];
>
> static int save_trace(struct stack_trace *trace)
> {
> trace->nr_entries = 0;
> - trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
> + trace->max_entries = CONFIG_MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
> trace->entries = stack_trace + nr_stack_trace_entries;
>
> trace->skip = 3;
> @@ -395,11 +395,11 @@ static int save_trace(struct stack_trace *trace)
>
> nr_stack_trace_entries += trace->nr_entries;
>
> - if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
> + if (nr_stack_trace_entries >= CONFIG_MAX_STACK_TRACE_ENTRIES-1) {
> if (!debug_locks_off_graph_unlock())
> return 0;
>
> - printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
> + printk("BUG: CONFIG_MAX_STACK_TRACE_ENTRIES = %d too low!\n", CONFIG_MAX_STACK_TRACE_ENTRIES);
> printk("turning off the locking correctness validator.\n");
> dump_stack();
>
> diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
> index a2ee95a..6887711 100644
> --- a/kernel/lockdep_internals.h
> +++ b/kernel/lockdep_internals.h
> @@ -61,12 +61,6 @@ enum {
>
> #define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
>
> -/*
> - * Stack-trace: tightly packed array of stack backtrace
> - * addresses. Protected by the hash_lock.
> - */
> -#define MAX_STACK_TRACE_ENTRIES 262144UL
> -
> extern struct list_head all_lock_classes;
> extern struct lock_chain lock_chains[];
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index cbf6e02..ad35402 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -509,6 +509,15 @@ config LOCKDEP
> select KALLSYMS
> select KALLSYMS_ALL
>
> +config MAX_STACK_TRACE_ENTRIES
> + int "MAX_STACK_TRACE_ENTRIES for LOCKDEP"
> + depends on LOCKDEP
> + default 262144
> + help
> + This option allows you to change the default MAX_STACK_TRACE_ENTRIES
> + used for LOCKDEP. Warning, increasing this number will increase the
> + size of the stack_trace array, and thus the kernel size too.
> +
> config LOCK_STAT
> bool "Lock usage statistics"
> depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
> --
> 1.6.6.1
>
>
I missed the MAX_STACK_TRACE_ENTRIES in kernel/lockdep_proc.c
This corrects that.
>From 66b4fa66afefb9e22047ddc5a68c9886e1a59cf6 Mon Sep 17 00:00:00 2001
From: John Kacur <jkacur@...hat.com>
Date: Fri, 16 Apr 2010 13:24:02 +0200
Subject: [PATCH] lockdep: Make MAX_STACK_TRACE_ENTRIES configurable.
Certain configurations that have LOCKDEP turned on, run into the limit
where the MAX_STACK_TRACE_ENTRIES are too small. Rather than simply
turning of the locking correctness validator let the user configure this
value to something reasonable for their system.
Signed-off-by: John Kacur <jkacur@...hat.com>
---
kernel/lockdep.c | 8 ++++----
kernel/lockdep_internals.h | 6 ------
kernel/lockdep_proc.c | 2 +-
lib/Kconfig.debug | 9 +++++++++
4 files changed, 14 insertions(+), 11 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 1199bda..6030521 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -368,12 +368,12 @@ static int verbose(struct lock_class *class)
* addresses. Protected by the graph_lock.
*/
unsigned long nr_stack_trace_entries;
-static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
+static unsigned long stack_trace[CONFIG_MAX_STACK_TRACE_ENTRIES];
static int save_trace(struct stack_trace *trace)
{
trace->nr_entries = 0;
- trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
+ trace->max_entries = CONFIG_MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
trace->entries = stack_trace + nr_stack_trace_entries;
trace->skip = 3;
@@ -395,11 +395,11 @@ static int save_trace(struct stack_trace *trace)
nr_stack_trace_entries += trace->nr_entries;
- if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
+ if (nr_stack_trace_entries >= CONFIG_MAX_STACK_TRACE_ENTRIES-1) {
if (!debug_locks_off_graph_unlock())
return 0;
- printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
+ printk("BUG: CONFIG_MAX_STACK_TRACE_ENTRIES = %d too low!\n", CONFIG_MAX_STACK_TRACE_ENTRIES);
printk("turning off the locking correctness validator.\n");
dump_stack();
diff --git a/kernel/lockdep_internals.h b/kernel/lockdep_internals.h
index a2ee95a..6887711 100644
--- a/kernel/lockdep_internals.h
+++ b/kernel/lockdep_internals.h
@@ -61,12 +61,6 @@ enum {
#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
-/*
- * Stack-trace: tightly packed array of stack backtrace
- * addresses. Protected by the hash_lock.
- */
-#define MAX_STACK_TRACE_ENTRIES 262144UL
-
extern struct list_head all_lock_classes;
extern struct lock_chain lock_chains[];
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index d4aba4f..97fcb31 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -306,7 +306,7 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
seq_printf(m, " in-process chains: %11u\n",
nr_process_chains);
seq_printf(m, " stack-trace entries: %11lu [max: %lu]\n",
- nr_stack_trace_entries, MAX_STACK_TRACE_ENTRIES);
+ nr_stack_trace_entries, CONFIG_MAX_STACK_TRACE_ENTRIES);
seq_printf(m, " combined max dependencies: %11u\n",
(nr_hardirq_chains + 1) *
(nr_softirq_chains + 1) *
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cbf6e02..ad35402 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -509,6 +509,15 @@ config LOCKDEP
select KALLSYMS
select KALLSYMS_ALL
+config MAX_STACK_TRACE_ENTRIES
+ int "MAX_STACK_TRACE_ENTRIES for LOCKDEP"
+ depends on LOCKDEP
+ default 262144
+ help
+ This option allows you to change the default MAX_STACK_TRACE_ENTRIES
+ used for LOCKDEP. Warning, increasing this number will increase the
+ size of the stack_trace array, and thus the kernel size too.
+
config LOCK_STAT
bool "Lock usage statistics"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
--
1.6.6.1
--
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