Re: [PATCH][V7]make get_user_pages interruptible

[Ying Han <yinghan@google.com>]

On Wed, Dec 3, 2008 at 7:03 AM, Lee Schermerhorn
<Lee.Schermerhorn@hp.com> wrote:
> On Tue, 2008-12-02 at 21:17 -0800, Ying Han wrote:
>> From: Ying Han <yinghan@google.com>
>>
>> make get_user_pages interruptible
>> The initial implementation of checking TIF_MEMDIE covers the cases of OOM
>> killing. If the process has been OOM killed, the TIF_MEMDIE is set and it
>> return immediately. This patch includes:
>>
>> 1. add the case that the SIGKILL is sent by user processes. The process can
>> try to get_user_pages() unlimited memory even if a user process has sent a
>> SIGKILL to it(maybe a monitor find the process exceed its memory limit and
>> try to kill it). In the old implementation, the SIGKILL won't be handled
>> until the get_user_pages() returns.
>>
>> 2. change the return value to be ERESTARTSYS. It makes no sense to return
>> ENOMEM if the get_user_pages returned by getting a SIGKILL signal.
>> Considering the general convention for a system call interrupted by a
>> signal is ERESTARTNOSYS, so the current return value is consistant to that.
>>
>> Signed-off-by:        Paul Menage <menage@google.com>
>> Signed-off-by:        Ying Han <yinghan@google.com>
>>
> <snip>
>
> Couple of things:
>
> * I tested your previous patch [that was "just too ugly to live
> with" :)] overnight with my swap/unevictable-lru/mlocked-pages stress
> test on both x86_64 and ia64.  I replaced the two patches in mmotm
> 081201 with the "ugly one".  Both systems ran for ~16:40 [hh:mm] without
> error, before I stopped the tests.
thanks Lee and the "swap/unevictable-lru/mlocked-pages" tests is somewhere
i can access? just curious.

> * Your patch--bailing out of get_user_pages() when current has SIGKILL
> pending--breaks munlock on exit when SIGKILL is pending.  This results
> in freeing of mlocked pages [not so bad, I guess] and possibly leaving,
> e.g., shared library pages mlocked and unevictable after last VM_LOCKED
> vma is removed.  I noticed this because SIGKILL is how the test harness
> kills off the running tests.  I have a patch that fixes this.  The
> overnight runs included this patch.  I'll post it after rebasing and a
> quick retest [he says optimistically] on mmotm-081203.
sorry not get exactly what you mean it breaks the munlock. :-)

> Lee
>
>

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