From: Vlastimil Babka <vbabka@suse.cz>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>,
Junil Lee <junil0814.lee@lge.com>,
ngupta@vflare.org, sergey.senozhatsky.work@gmail.com,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] zsmalloc: fix migrate_zspage-zs_free race condition
Date: Sat, 16 Jan 2016 08:44:09 +0100 [thread overview]
Message-ID: <5699F4C9.1070902@suse.cz> (raw)
In-Reply-To: <20160116040913.GA566@swordfish>
On 16.1.2016 5:09, Sergey Senozhatsky wrote:
> On (01/15/16 16:49), Vlastimil Babka wrote:
> [..]
>>
>> Could you please also help making the changelog more clear?
>>
>>>
>>>> + free_obj |= BIT(HANDLE_PIN_BIT);
>>>> record_obj(handle, free_obj);
>>
>> I think record_obj() should use WRITE_ONCE() or something like that.
>> Otherwise the compiler is IMHO allowed to reorder this, i.e. first to assign
>> free_obj to handle, and then add the PIN bit there.
>
> good note.
>
> ... or do both things in record_obj() (per Minchan)
>
> record_obj(handle, obj)
> {
> *(unsigned long)handle = obj & ~(1<<HANDLE_PIN_BIT);
Hmm but that's an unpin, not a pin? A mistake or I'm missing something?
Anyway the compiler can do the same thing here without a WRITE_ONCE().
> }
>
> -ss
>
> --
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>
next prev parent reply other threads:[~2016-01-16 7:44 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 7:39 [PATCH v2] zsmalloc: fix migrate_zspage-zs_free race condition Junil Lee
2016-01-15 14:34 ` Minchan Kim
2016-01-15 15:49 ` Vlastimil Babka
2016-01-16 4:09 ` Sergey Senozhatsky
2016-01-16 7:44 ` Vlastimil Babka [this message]
2016-01-16 8:06 ` Sergey Senozhatsky
2016-01-16 8:16 ` Vlastimil Babka
2016-01-16 10:05 ` Sergey Senozhatsky
2016-01-18 1:02 ` Junil Lee
2016-01-18 6:32 ` Minchan Kim
2016-01-18 7:04 ` Sergey Senozhatsky
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