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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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