On Mon, 19 Apr 2010 18:51:57 +0200 (CEST)
John Kacur <jkacur@xxxxxxxxx> wrote:
> Ingo, since nobody responded to my RFC, I am assuming that the change
> is not controversial, would you please consider pulling this into tip
> for 2.6.35?
>
> What followed is v2 of the patch regenerated against the latest
> tip/master
>
> ...
>
> 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@xxxxxxxxxx>
> ---
> 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 78325f8..2acc25d 100644
> --- a/kernel/lockdep.c
> +++ b/kernel/lockdep.c
> @@ -369,12 +369,12 @@ 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;
> @@ -396,11 +396,11 @@ 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 8d7d4b6..e2585ff 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 59b76c8..924e0e9 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) *
Note that MAX_STACK_TRACE_ENTRIES was `unsigned long', but
CONFIG_MAX_STACK_TRACE_ENTRIES is now an `int'. AFACIT all the
comparisons will handle that OK, but please review them for this.
But this seq_printf() is now wrong, isn't it? Didn't it generate a
long-vs-int compiler warning?
<tests it>
yup:
kernel/lockdep_proc.c: In function 'lockdep_stats_show':
kernel/lockdep_proc.c:309: warning: format '%lu' expects type 'long unsigned int', but argument 4 has type 'int'
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 0bbd5c7..38d3bf3 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -533,6 +533,15 @@ 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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