On 12/16/2016 03:32 PM, Michal Hocko wrote:
On Fri 16-12-16 15:25:27, Vegard Nossum wrote:
On 12/16/2016 03:00 PM, Michal Hocko wrote:
On Fri 16-12-16 14:14:17, Vegard Nossum wrote:
[...]
Out of memory: Kill process 1650 (trinity-main) score 90 or sacrifice child
Killed process 1724 (trinity-c14) total-vm:37280kB, anon-rss:236kB,
file-rss:112kB, shmem-rss:112kB
BUG: unable to handle kernel NULL pointer dereference at 00000000000001e8
IP: [<ffffffff8126b1c0>] copy_process.part.41+0x2150/0x5580
PGD c001067 PUD c000067
PMD 0
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
(ftrace buffer empty)
CPU: 28 PID: 1650 Comm: trinity-main Not tainted 4.9.0-rc6+ #317
Hmm, so this was the oom victim initially but we have decided to kill
its child 1724 instead.
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
task: ffff88000f9bc440 task.stack: ffff88000c778000
RIP: 0010:[<ffffffff8126b1c0>] [<ffffffff8126b1c0>]
copy_process.part.41+0x2150/0x5580
Could you match this to the kernel source please?
kernel/fork.c:629 dup_mmap()
Ok, so this is before the child is made visible so the oom reaper
couldn't have seen it.
it's atomic_dec(&inode->i_writecount), it matches up with
file_inode(file) == NULL:
(gdb) p &((struct inode *)0)->i_writecount
$1 = (atomic_t *) 0x1e8 <irq_stack_union+488>
is this a p9 inode?
When I looked at this before it always crashed in this spot for the very
first VMA in the mm (which happens to be the exe, which is on a 9p root fs).
I added a trace_printk() to dup_mmap() to print inode->i_sb->s_type and
the last thing I see for a new crash in the same place is:
trinity--9280 28.... 136345090us : copy_process.part.41: ffffffff8485ec40
---------------------------------
CPU: 0 PID: 9302 Comm: trinity-c0 Not tainted 4.9.0-rc8+ #332
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
task: ffff880000070000 task.stack: ffff8800099e0000
RIP: 0010:[<ffffffff8126c7c9>] [<ffffffff8126c7c9>]
copy_process.part.41+0x22c9/0x55b0
As you can see, the addresses match:
(gdb) p &v9fs_fs_type
$1 = (struct file_system_type *) 0xffffffff8485ec40 <v9fs_fs_type>
So I think we can safely say that yes, it's a p9 inode.
Vegard
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