From: Andrew Morton <akpm@linux-foundation.org>
To: Adrian Huang <adrianhuang0701@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Uladzislau Rezki <urezki@gmail.com>,
kasan-dev@googlegroups.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Adrian Huang <ahuang12@lenovo.com>
Subject: Re: [PATCH 1/1] kasan, vmalloc: avoid lock contention when depopulating vmalloc
Date: Wed, 25 Sep 2024 13:47:06 -0700 [thread overview]
Message-ID: <20240925134706.2a0c2717a41a338d938581ff@linux-foundation.org> (raw)
In-Reply-To: <20240925134732.24431-1-ahuang12@lenovo.com>
On Wed, 25 Sep 2024 21:47:32 +0800 Adrian Huang <adrianhuang0701@gmail.com> wrote:
>
> ...
>
> From: Adrian Huang <ahuang12@lenovo.com>
> After re-visiting code path about setting the kasan ptep (pte pointer),
> it's unlikely that a kasan ptep is set and cleared simultaneously by
> different CPUs. So, use ptep_get_and_clear() to get rid of the spinlock
> operation.
"unlikely" isn't particularly comforting. We'd prefer to never corrupt
pte's!
I'm suspecting we need a more thorough solution here.
btw, for a lame fix, did you try moving the spin_lock() into
kasan_release_vmalloc(), around the apply_to_existing_page_range()
call? That would at least reduce locking frequency a lot. Some
mitigation might be needed to avoid excessive hold times.
next prev parent reply other threads:[~2024-09-25 20:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-25 13:47 Adrian Huang
2024-09-25 20:47 ` Andrew Morton [this message]
2024-09-26 12:22 ` Huang Adrian
2024-09-26 16:16 ` Uladzislau Rezki
2024-09-30 9:49 ` Huang Adrian
2024-09-30 15:22 ` Uladzislau Rezki
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