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From: Christopher Lameter <cl@linux.com>
To: Yu Zhao <yuzhao@google.com>
Cc: Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	 Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	 "Kirill A . Shutemov" <kirill@shutemov.name>,
	 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	linux-mm@kvack.org,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 4/4] mm: lock slub page when listing objects
Date: Fri, 13 Sep 2019 14:58:51 +0000
Message-ID: <0100016d2b224ef4-8660f7e9-3093-48fa-bc40-63d20e9f2444-000000@email.amazonses.com> (raw)
In-Reply-To: <20190912023111.219636-4-yuzhao@google.com>

On Wed, 11 Sep 2019, Yu Zhao wrote:

> Though I have no idea what the side effect of such race would be,
> apparently we want to prevent the free list from being changed
> while debugging the objects.

process_slab() is called under the list_lock which prevents any allocation
from the free list in the slab page. This means that new objects can be
added to the freelist which occurs by updating the freelist pointer in the
slab page with a pointer to the newly free object which in turn contains
the old freelist pointr.

It is therefore possible to safely traverse the objects on the freelist
after the pointer has been retrieved

NAK.



  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09  6:10 [PATCH] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-09 16:00 ` Kirill A. Shutemov
     [not found]   ` <e5e25aa3-651d-92b4-ac82-c5011c66a7cb@I-love.SAKURA.ne.jp>
2019-09-09 21:39     ` Yu Zhao
     [not found]       ` <201909100141.x8A1fVdu048305@www262.sakura.ne.jp>
2019-09-10  2:16         ` Yu Zhao
2019-09-10  9:16       ` Kirill A. Shutemov
2019-09-11 14:13 ` Andrew Morton
2019-09-12  0:29   ` [PATCH 1/3] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  0:29     ` [PATCH 2/3] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12  0:44       ` Kirill A. Shutemov
2019-09-12  1:31         ` Yu Zhao
2019-09-12  2:31         ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Yu Zhao
2019-09-12  2:31           ` [PATCH v2 2/4] mm: clean up validate_slab() Yu Zhao
2019-09-12  9:46             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 3/4] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-12 10:04             ` Kirill A. Shutemov
2019-09-12  2:31           ` [PATCH v2 4/4] mm: lock slub page when listing objects Yu Zhao
2019-09-12 10:06             ` Kirill A. Shutemov
2019-09-12 21:12               ` Yu Zhao
2019-09-13 14:58             ` Christopher Lameter [this message]
2019-09-12  9:40           ` [PATCH v2 1/4] mm: correct mask size for slub page->objects Kirill A. Shutemov
2019-09-12 21:11             ` Yu Zhao
2019-09-12 22:03               ` Kirill A. Shutemov
2019-09-14  0:07           ` [PATCH v3 1/2] mm: clean up validate_slab() Yu Zhao
2019-09-14  0:07             ` [PATCH v3 2/2] mm: avoid slub allocation while holding list_lock Yu Zhao
2019-09-16  8:39             ` [PATCH v3 1/2] mm: clean up validate_slab() Kirill A. Shutemov
2019-09-12  0:29     ` [PATCH 3/3] mm: lock slub page when listing objects Yu Zhao

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