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    SubjectRe: [PATCH 5/5] x86,mm: make pagefault killable
    On Tue, 22 Mar 2011 20:09:29 +0900 (JST)
    KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

    > When oom killer occured, almost processes are getting stuck following
    > two points.
    >
    > 1) __alloc_pages_nodemask
    > 2) __lock_page_or_retry
    >
    > 1) is not much problematic because TIF_MEMDIE lead to make allocation
    > failure and get out from page allocator. 2) is more problematic. When
    > OOM situation, Zones typically don't have page cache at all and Memory
    > starvation might lead to reduce IO performance largely. When fork bomb
    > occur, TIF_MEMDIE task don't die quickly mean fork bomb may create
    > new process quickly rather than oom-killer kill it. Then, the system
    > may become livelock.
    >
    > This patch makes pagefault interruptible by SIGKILL.
    >
    > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > ---
    > arch/x86/mm/fault.c | 9 +++++++++
    > include/linux/mm.h | 1 +
    > mm/filemap.c | 22 +++++++++++++++++-----
    > 3 files changed, 27 insertions(+), 5 deletions(-)
    >
    > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
    > index 20e3f87..797c7d0 100644
    > --- a/arch/x86/mm/fault.c
    > +++ b/arch/x86/mm/fault.c
    > @@ -1035,6 +1035,7 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
    > if (user_mode_vm(regs)) {
    > local_irq_enable();
    > error_code |= PF_USER;
    > + flags |= FAULT_FLAG_KILLABLE;
    > } else {
    > if (regs->flags & X86_EFLAGS_IF)
    > local_irq_enable();
    > @@ -1138,6 +1139,14 @@ good_area:
    > }
    >
    > /*
    > + * Pagefault was interrupted by SIGKILL. We have no reason to
    > + * continue pagefault.
    > + */
    > + if ((flags & FAULT_FLAG_KILLABLE) && (fault & VM_FAULT_RETRY) &&
    > + fatal_signal_pending(current))
    > + return;
    > +

    Hmm? up_read(&mm->mmap_sem) ?

    Thanks,
    -Kame




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