Re: [patch] procfs: provide stack information for threads

Andrew Morton
2009-06-04T11:39:18Z

On Thu, 04 Jun 2009 13:23:48 +0200 Stefani Seibold <stefani@seibold.net> wrote:

> Hi everybody,
>
> This is the latest version of the formaly named "detailed stack info"
> patch which give you a better overview of the userland application stack
> usage, especially for embedded linux.
>
> Currently you are only able to dump the main process/thread stack usage
> which is showed in /proc/pid/status by the "VmStk" Value. But you get no
> information about the consumed stack memory of the the threads.
>
> There is an enhancement in the /proc/<pid>/{task/*,}/*maps and which
> marks the vm mapping where the thread stack pointer reside with "[thread
> stack xxxxxxxx]". xxxxxxxx is the start address of the stack.
>
> Also there is a new entry "stack usage" in /proc/<pid>/{task/*,}/status
> which will you give the current stack usage in kb.
>
> I also fixed stack base address in /proc/<pid>/task/*/stat to the base
> address of the associated thread stack and not the one of the main
> process. This makes more sense.
>
> Changes since last posting:
>
> - Redesigned everything what was suggested by Andrew

You didn't account for some of my comments. I'll repeat the ones which
I recall below.

> - slime done

What's "slime"?

> +static inline unsigned long get_stack_usage_in_bytes(struct vm_area_struct *vma,
> + struct task_struct *p)
> +{
> + unsigned long i;
> + struct page *page;
> + unsigned long stkpage;
> +
> + stkpage = KSTK_ESP(p) & PAGE_MASK;
> +
> +#ifdef CONFIG_STACK_GROWSUP
> + for (i = vma->vm_end; i-PAGE_SIZE > stkpage; i -= PAGE_SIZE) {
> +
> + page = follow_page(vma, i-PAGE_SIZE, 0);
> +
> + if (!IS_ERR(page) && page)

Shouldn't this be !page?

> + break;
> + }
> + return i - (p->stack_start & PAGE_MASK);
> +#else
> + for (i = vma->vm_start; i+PAGE_SIZE <= stkpage; i += PAGE_SIZE) {
> +
> + page = follow_page(vma, i, 0);
> +
> + if (!IS_ERR(page) && page)

Ditto

> + break;
> + }
> + return (p->stack_start & PAGE_MASK) - i + PAGE_SIZE;
> +#endif
> +}
> +
> +static inline void task_show_stack_usage(struct seq_file *m,
> + struct task_struct *p)
> +{
> + struct vm_area_struct *vma;
> + struct mm_struct *mm;
> +
> + mm = get_task_mm(p);
> +
> + if (mm) {
> + vma = find_vma(mm, p->stack_start);
> +
> + if (vma)
> + seq_printf(m, "Stack usage:\t%lu kB\n",
> + get_stack_usage_in_bytes(vma, p) >> 10);
> +
> + mmput(mm);
> + }
> +}
> +
> int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
> struct pid *pid, struct task_struct *task)
> {
> @@ -340,6 +389,7 @@
> task_show_regs(m, task);
> #endif
> task_context_switch_counts(m, task);
> + task_show_stack_usage(m, task);
> return 0;
> }
>
> @@ -481,7 +531,7 @@
> rsslim,
> mm ? mm->start_code : 0,
> mm ? mm->end_code : 0,
> - (permitted && mm) ? mm->start_stack : 0,
> + (permitted) ? task->stack_start : 0,
> esp,
> eip,
> /* The signal information here is obsolete.
> diff -u -N -r linux-2.6.30.orig/fs/proc/task_mmu.c linux-2.6.30/fs/proc/task_mmu.c
> --- linux-2.6.30.orig/fs/proc/task_mmu.c 2009-06-04 09:29:47.000000000 +0200
> +++ linux-2.6.30/fs/proc/task_mmu.c 2009-06-04 09:32:35.000000000 +0200
> @@ -242,6 +242,20 @@
> } else if (vma->vm_start <= mm->start_stack &&
> vma->vm_end >= mm->start_stack) {
> name = "[stack]";
> + } else {
> + unsigned long stack_start;
> +
> + stack_start =
> + ((struct proc_maps_private *)
> + m->private)->task->stack_start;

I'd suggested a clearer/cleaner way of implementing this.

> + if (vma->vm_start <= stack_start &&
> + vma->vm_end >= stack_start) {
> + pad_len_spaces(m, len);
> + seq_printf(m,
> + "[thread stack: %08lx]",
> + stack_start);
> + }
> }
> } else {
> name = "[vdso]";
> diff -u -N -r linux-2.6.30.orig/include/linux/sched.h linux-2.6.30/include/linux/sched.h
> --- linux-2.6.30.orig/include/linux/sched.h 2009-06-04 09:29:47.000000000 +0200
> +++ linux-2.6.30/include/linux/sched.h 2009-06-04 09:32:35.000000000 +0200
> @@ -1429,6 +1429,7 @@
> /* state flags for use by tracers */
> unsigned long trace;
> #endif
> + unsigned long stack_start;
> };
>
> /* Future-safe accessor for struct task_struct's cpus_allowed. */
> diff -u -N -r linux-2.6.30.orig/kernel/fork.c linux-2.6.30/kernel/fork.c
> --- linux-2.6.30.orig/kernel/fork.c 2009-06-04 09:29:47.000000000 +0200
> +++ linux-2.6.30/kernel/fork.c 2009-06-04 13:15:35.000000000 +0200
> @@ -1092,6 +1092,8 @@
> if (unlikely(current->ptrace))
> ptrace_fork(p, clone_flags);
>
> + p->stack_start = stack_start;

OK, that got simpler.

> Signed-off-by: Stefani Seibold <stefani@seibold.net>

This should be positioned at the end of the changelog, ahead of the
patch itself.