linux-kernel - Re: kmemleak: Early log buffer exceeded (525980) during boot

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Date:   Wed, 5 Dec 2018 15:38:51 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     cai@....us
Cc:     Catalin Marinas <catalin.marinas@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Will Deacon <will.deacon@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: kmemleak: Early log buffer exceeded (525980) during boot

On Wed, Nov 28, 2018 at 5:21 AM Qian Cai <cai@....us> wrote:
> On 11/10/18 11:59 AM, Catalin Marinas wrote:
> > On Sat, Nov 10, 2018 at 10:08:10AM -0500, Qian Cai wrote:
> >> On Nov 8, 2018, at 4:23 PM, Qian Cai <cai@....us> wrote:
> >>> The maximum value for DEBUG_KMEMLEAK_EARLY_LOG_SIZE is only 40000, so it
> >>> disables kmemleak every time on this aarch64 server running the latest mainline
> >>> (b00d209).
> >>>
> >>> # echo scan > /sys/kernel/debug/kmemleak
> >>> -bash: echo: write error: Device or resource busy
> >>>
> >>> Any idea on how to enable kmemleak there?
> >>
> >> I have managed to hard-code DEBUG_KMEMLEAK_EARLY_LOG_SIZE to 600000,
> >
> > That's quite a high number, I wouldn't have thought it is needed.
> > Basically the early log buffer is only used until the slub allocator
> > gets initialised and kmemleak_init() is called from start_kernel(). I
> > don't know what allocates that much memory so early.
> >
>
> It turned out that kmemleak does not play well with KASAN on those aarch64 (HPE
> Apollo 70 and Huawei TaiShan 2280) servers.
>
> After calling start_kernel()->setup_arch()->kasan_init(), kmemleak early log
> buffer went from something like from 280 to 260000. The multitude of
> kmemleak_alloc() calls is,
>
> for_each_memblock(memory, reg) x \
> while (pgdp++, addr = next, addr != end) x \
> while (ptep++, addr = next, addr != end && \ pte_none(READ_ONCE(*ptep)))
>
> Is this expected?


FTR, this should be resolved by (if put pieces together correctly):
https://lkml.org/lkml/2018/11/29/191