Re: [PATCH][V7]make get_user_pages interruptible

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

On Wed, 2008-12-03 at 12:25 -0800, Ying Han wrote:
> 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.

Take a look in http://free.linux.hp.com/~lts/Temp at the usex-vmstress
README.  I'm going to update these "real soon now" with later versions
of the sub-tests.  Note that the tarball contains binaries for
convenience.  You can grab all of the programs' sources and build
yourself, but I created the x86_64 binary tarball for Rik and Kosaki-san
during the split-lru/unevictable-lru development.  Even with the
binaries, there's a fair bit of setup described--sufficiently, I
hope--in the README.

I should add an ia64 tarball as well, as this test seems to sniff out
quite a few vm races and such.


> 
> > * 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. :-)

See the "ignore sigkill in get_user_pages..." patch I just posted.

Lee


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