Re: [PATCH][V7]make get_user_pages interruptible

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

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.

* 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.  

Lee

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