linux-kernel - Re: [PATCH] xtensa: improve stack dumping

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Message-ID: <78ff494e-2fe2-b881-29ca-84992e26d415@arista.com>
Date:   Wed, 6 Nov 2019 22:18:45 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     Max Filippov <jcmvbkbc@...il.com>
Cc:     "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>, Chris Zankel <chris@...kel.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH] xtensa: improve stack dumping

On 11/6/19 10:00 PM, Max Filippov wrote:
> On Wed, Nov 6, 2019 at 12:51 PM Dmitry Safonov <dima@...sta.com> wrote:
>> On 11/6/19 6:16 PM, Max Filippov wrote:
>>> @@ -512,10 +510,12 @@ void show_stack(struct task_struct *task, unsigned long *sp)
>>>       for (i = 0; i < kstack_depth_to_print; i++) {
>>>               if (kstack_end(sp))
>>>                       break;
>>> -             pr_cont(" %08lx", *sp++);
>>> +             sprintf(buf + (i % 8) * 9, " %08lx", *sp++);
>>
>> buf is on the stack, does sprintf() put null-terminator for hex?
> 
> It should put null-terminator regardless of the format string.

Always unsure what to expect from printf() :)

> 
>>>               if (i % 8 == 7)
>>> -                     pr_cont("\n");
>>> +                     pr_info("%s\n", buf);
>>>       }
>>> +     if (i % 8)
>>> +             pr_info("%s\n", buf);
>>
>> If the stack trace ends with (i % 8 == 7), you'll double-print the last
>> line?
> 
> No, I don't think so. 'For' loop condition is checked after i++, so if
> loop ends with i % 8 == 7 then its last iteration was done with
> i % 8 == 6 and thus the buf haven't been printed.

Ah, right - me being stupid.

Thanks,
          Dmitry