linux-kernel - Re: [PATCH] x86/unwind_guess: Prevent using UNWINDER

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Message-ID: <20171130135727.zy3nfdeodtkybzff@treble>
Date:   Thu, 30 Nov 2017 07:57:27 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, xiaolong.ye@...el.com,
        fengguang.wu@...el.com
Subject: Re: [PATCH] x86/unwind_guess: Prevent using UNWINDER_GUESS=y with
 STACKDEPOT=y

On Thu, Nov 30, 2017 at 03:35:54PM +0300, Andrey Ryabinin wrote:
> Stackdepot doesn't work well with CONFIG_UNWINDER_GUESS=y.
> The 'guess' unwinder generate awfully large and inaccurate stacktraces,
> thus stackdepot can't deduplicate stacktraces because they all look like
> unique. Eventually stackdepot reaches its capacity limit:
> 
> WARNING: CPU: 0 PID: 545 at lib/stackdepot.c:119 depot_save_stack+0x28e/0x550
> Call Trace:
>  ? kasan_kmalloc+0x144/0x160
>  ? depot_save_stack+0x1f5/0x550
>  ? do_raw_spin_unlock+0xda/0xf0
>  ? preempt_count_sub+0x13/0xc0
> 
> <...90 lines...>
> 
>  ? do_raw_spin_unlock+0xda/0xf0
> 
> Add STACKDEPOT=n dependency to UNWINDER_GUESS to avoid the problem.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Reported-by: kernel test robot <xiaolong.ye@...el.com>
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh