OOM killer hung the whole system

[Rock Lee]

On Tue, Jul 25, 2017 at 7:29 PM, Yubin Ruan <ablacktshirt at gmail.com> wrote:

> 2017-07-25 17:59 GMT+08:00 Rock Lee <rockdotlee at gmail.com>:
> > Hi,
> >
> > I was using a program to test OOM killer, but OOM killer hung my board.
> The
> > test snippet is very simple, just malloc() without free().
> >
> >   6         int i=0;
> >   7         char *ptrtest=NULL;
> >   8          while (1)
> >   9          {
> >  10                    ptrtest = malloc(0x1000);
> >  11                    if (ptrtest == NULL)
> >  12                        printf("malloc failed.\n");
> >  13          }
> >  14          return 0;
> >  15
> >
> > After I executed this program(a.out), there is no reaction of my shell.
> Only
> > this messege was shown:
> >
> > [  180.138188] Out of memory: Kill process 2706 (qq) score 623 or
> sacrifice
> > child
> > [  180.164230] Killed process 2706 (qq) total-vm:98156kB,
> anon-rss:96400kB,
> > file-rss:4kB
> >
> > I think it must be some problem with OOM killer, and tried a lot of way
> to
> > get some infomation. And I got this:
> >
> > =======================================================
> > Process: a.out, cpu: 0 pid: 1463 start: 0xd5849b00
> > =====================================================
> >     Task name: a.out pid: 1463 cpu: 0
> >     state: 0x2 exit_state: 0x0 stack base: 0xd6190000
> >     Stack:
> >     [<c08394e4>] __schedule+0x2c8
> >     [<c018df88>] squashfs_cache_get+0x108
> >     [<c0191020>] squashfs_readpage_block+0x28
> >     [<c018f648>] squashfs_readpage+0x624
> >     [<c0090d4c>] __do_page_cache_readahead+0x228
> >     [<c00882f4>] filemap_fault+0x1d4
> >     [<c00a5f10>] __do_fault+0x34
> >     [<c00a8ab0>] do_read_fault+0x19c
> >     [<c00a9388>] handle_mm_fault+0x468
> >     [<c00164b0>] do_page_fault+0x11c
> >     [<c00084a4>] do_PrefetchAbort+0x34
> >     [<c0011c1c>] ret_from_exception+0x0
> >
> > I am suprised, because a.out is in /tmp, there is no relation between
> a.out
> > and squashfs(my rootfs). Could anyone give me a hint ? Is the problem of
> > squashfs or OOM killer.
>
> You say your rootfs is squashfs filesystem. Is /tmp using the same
> device and same filesystem (i.e., squashfs) ?


Not exactly, /tmp uses tmpfs, but my rootfs uses squashfs.



-- 
Cheers,
Rock
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