linux-kernel - Re: [PATCH 2/6] mm/kasan: don't reduce quarantine in atomic contexts

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Date:	Tue, 2 Aug 2016 13:42:20 +0200
From:	Alexander Potapenko <glider@...gle.com>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Sasha Levin <alexander.levin@...izon.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 2/6] mm/kasan: don't reduce quarantine in atomic contexts

On Mon, Aug 1, 2016 at 4:45 PM, Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:
> Currently we call quarantine_reduce() for ___GFP_KSWAPD_RECLAIM
> (implied by __GFP_RECLAIM) allocation. So, basically we call it on
> almost every allocation. quarantine_reduce() sometimes is heavy operation,
> and calling it with disabled interrupts may trigger hard LOCKUP:
>
>  NMI watchdog: Watchdog detected hard LOCKUP on cpu 2irq event stamp: 1411258
>  Call Trace:
>   <NMI>  [<ffffffff98a48532>] dump_stack+0x68/0x96
>   [<ffffffff98357fbb>] watchdog_overflow_callback+0x15b/0x190
>   [<ffffffff9842f7d1>] __perf_event_overflow+0x1b1/0x540
>   [<ffffffff98455b14>] perf_event_overflow+0x14/0x20
>   [<ffffffff9801976a>] intel_pmu_handle_irq+0x36a/0xad0
>   [<ffffffff9800ba4c>] perf_event_nmi_handler+0x2c/0x50
>   [<ffffffff98057058>] nmi_handle+0x128/0x480
>   [<ffffffff980576d2>] default_do_nmi+0xb2/0x210
>   [<ffffffff980579da>] do_nmi+0x1aa/0x220
>   [<ffffffff99a0bb07>] end_repeat_nmi+0x1a/0x1e
>   <<EOE>>  [<ffffffff981871e6>] __kernel_text_address+0x86/0xb0
>   [<ffffffff98055c4b>] print_context_stack+0x7b/0x100
>   [<ffffffff98054e9b>] dump_trace+0x12b/0x350
>   [<ffffffff98076ceb>] save_stack_trace+0x2b/0x50
>   [<ffffffff98573003>] set_track+0x83/0x140
>   [<ffffffff98575f4a>] free_debug_processing+0x1aa/0x420
>   [<ffffffff98578506>] __slab_free+0x1d6/0x2e0
>   [<ffffffff9857a9b6>] ___cache_free+0xb6/0xd0
>   [<ffffffff9857db53>] qlist_free_all+0x83/0x100
>   [<ffffffff9857df07>] quarantine_reduce+0x177/0x1b0
>   [<ffffffff9857c423>] kasan_kmalloc+0xf3/0x100
>
> Reduce the quarantine_reduce iff direct reclaim is allowed.
>
> Fixes: 55834c59098d("mm: kasan: initial memory quarantine implementation")
> Reported-by: Dave Jones <davej@...emonkey.org.uk>
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
Acked-by: Alexander Potapenko <glider@...gle.com>
> ---
>  mm/kasan/kasan.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
> index 3019cec..c99ef40 100644
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -565,7 +565,7 @@ void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
>         unsigned long redzone_start;
>         unsigned long redzone_end;
>
> -       if (flags & __GFP_RECLAIM)
> +       if (gfpflags_allow_blocking(flags))
>                 quarantine_reduce();
>
>         if (unlikely(object == NULL))
> @@ -596,7 +596,7 @@ void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
>         unsigned long redzone_start;
>         unsigned long redzone_end;
>
> -       if (flags & __GFP_RECLAIM)
> +       if (gfpflags_allow_blocking(flags))
>                 quarantine_reduce();
>
>         if (unlikely(ptr == NULL))
> --
> 2.7.3
>



-- 
Alexander Potapenko
Software Engineer

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