Re: [patch] add /proc/pid/stack to dump task's stack trace

[Alexey Dobriyan <adobriyan@gmail.com>]

On Thu, Nov 06, 2008 at 11:01:39AM -0800, Ken Chen wrote:
> This patch adds the ability to query a task's stack trace via /proc/pid/stack.
> It is considered to be more useful than /proc/pid/wchan as it provides full
> stack trace instead of single depth.

Please, name handler proc_pid_stack following current convention.
And drop space before casts.

> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -338,6 +339,35 @@ static int proc_pid_wchan
>  	else
>  		return sprintf(buffer, "%s", symname);
>  }
> +
> +#define MAX_STACK_TRACE_DEPTH	32
> +static int proc_stack_trace(struct task_struct *task, char *buffer)
> +{
> +	int i, len = 0;
> +	unsigned long *entries;
> +	struct stack_trace trace;
> +
> +	entries = kmalloc(sizeof(*entries) * MAX_STACK_TRACE_DEPTH, GFP_KERNEL);
> +	if (!entries)
> +		goto out;
> +
> +	trace.nr_entries = 0;
> +	trace.max_entries = MAX_STACK_TRACE_DEPTH;
> +	trace.entries = entries;
> +	trace.skip = 0;
> +
> +	read_lock(&tasklist_lock);
> +	save_stack_trace_tsk(task, &trace);
> +	read_unlock(&tasklist_lock);
> +
> +	for (i = 0; i < trace.nr_entries; i++) {
> +		len += sprintf(buffer + len, "[<%p>] %pS\n",
> +				(void *) entries[i], (void *) entries[i]);
> +	}
> +	kfree(entries);
> +out:
> +	return len;
> +}
>  #endif /* CONFIG_KALLSYMS */
> 
>  #ifdef CONFIG_SCHEDSTATS
> @@ -2489,6 +2519,7 @@ static const struct pid_entry tgid_base_stuff[] = {
>  	DIR("attr",       S_IRUGO|S_IXUGO, attr_dir),
>  #endif
>  #ifdef CONFIG_KALLSYMS
> +	INF("stack",      S_IRUSR, stack_trace),
>  	INF("wchan",      S_IRUGO, pid_wchan),
>  #endif
>  #ifdef CONFIG_SCHEDSTATS