linux-kernel - Re: [PATCH][V3]Make get_user

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Date:	Mon, 24 Nov 2008 13:02:45 -0800
From:	Ying Han <yinghan@...gle.com>
To:	Paul Menage <menage@...gle.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Rohit Seth <rohitseth@...gle.com>
Subject: Re: [PATCH][V3]Make get_user_pages interruptible

On Mon, Nov 24, 2008 at 12:02 PM, Paul Menage <menage@...gle.com> wrote:
> On Fri, Nov 21, 2008 at 5:31 PM, Ying Han <yinghan@...gle.com> wrote:
>> From: Paul Menage <menage@...gle.com>
>
> This patch is getting further and further from my original internal
> changes, so I'm not sure that a From: line from me is appropriate.
>
>>                         */
>> -                       if (unlikely(test_tsk_thread_flag(tsk, TIF_MEMDIE)))
>> -                               return i ? i : -ENOMEM;
>> +                       if (unlikely(sigkill_pending(tsk)))
>> +                               return i ? i : -ERESTARTSYS;
>
> You've changed the check from sigkill_pending(current) to sigkill_pending(tsk).
>
> I originally made that sigkill_pending(current) since we want to avoid
> tasks entering an unkillable state just because they're doing
> get_user_pages() on a system that's short of memory. Admittedly for
> the main case that we care about, mlock() (or an mmap() with
> MCL_FUTURE set) then tsk==current, but philosophically it seems to me
> to be more correct to do the check against current than tsk, since
> current is the thing that's actually allocating the memory. But maybe
> it would be better to check both?
In most of cases, tsk==current in get_user_pages(), that is why i
change current to tsk since
tsk is a superset of current, no? If that is right, why we need to check both?
>
> Paul
>
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