linux-kernel - Re: multi-threads libvmmalloc fork test hang

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Date:   Thu, 27 Oct 2016 15:37:20 +0200
From:   Jan Kara <jack@...e.cz>
To:     Xiong Zhou <xzhou@...hat.com>
Cc:     linux-nvdimm@...1.01.org, jack@...e.cz,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: multi-threads libvmmalloc fork test hang

Thanks for the report. I'll try to reproduce it...

								Honza

On Thu 27-10-16 19:22:30, Xiong Zhou wrote:
> # description
> 
> nvml test suite vmmalloc_fork test hang.
> 
> $ ps -eo stat,comm  | grep vmma
> S+   vmmalloc_fork
> Sl+  vmmalloc_fork
> Z+   vmmalloc_fork <defunct>
> Sl+  vmmalloc_fork
> Z+   vmmalloc_fork <defunct>
> Z+   vmmalloc_fork <defunct>
> Sl+  vmmalloc_fork
> Z+   vmmalloc_fork <defunct>
> Z+   vmmalloc_fork <defunct>
> Z+   vmmalloc_fork <defunct>
> 
> dmesg:
> 
> [  250.499097] INFO: task vmmalloc_fork:9805 blocked for more than 120 seconds.
> [  250.530667]       Not tainted 4.9.09fe68ca+ #27
> [  250.550901] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [  250.585752] vmmalloc_fork   D[  250.598362]  ffffffff8171813c     0  9805   9765 0x00000080
> [  250.623445]  ffff88075dc68f80[  250.636052]  0000000000000000 ffff88076058db00 ffff88017c5b0000 ffff880763b19340[  250.668510]  ffffc9000fe1bbb0 ffffffff8171813c ffffc9000fe1bc20 ffffc9000fe1bbe0[  250.704220]  ffffffff82248898 ffff88076058db00 ffffffff82248898Call Trace:
> [  250.738382]  [<ffffffff8171813c>] ? __schedule+0x21c/0x6a0
> [  250.763404]  [<ffffffff817185f6>] schedule+0x36/0x80
> [  250.786177]  [<ffffffff81284471>] get_unlocked_mapping_entry+0xc1/0x120
> [  250.815869]  [<ffffffff81283810>] ? iomap_dax_rw+0x110/0x110
> [  250.841350]  [<ffffffff81284c0a>] grab_mapping_entry+0x4a/0x220
> [  250.868442]  [<ffffffff812851e9>] iomap_dax_fault+0xa9/0x3b0
> [  250.894437]  [<ffffffffa02b15fe>] xfs_filemap_fault+0xce/0xf0 [xfs]
> [  250.922805]  [<ffffffff811d3159>] __do_fault+0x79/0x100
> [  250.947035]  [<ffffffff811d7a2b>] do_fault+0x49b/0x690
> [  250.970964]  [<ffffffffa02b146c>] ? xfs_filemap_pmd_fault+0x9c/0x160 [xfs]
> [  251.001812]  [<ffffffff811d94ba>] handle_mm_fault+0x61a/0xa50
> [  251.027736]  [<ffffffff8106c3da>] __do_page_fault+0x22a/0x4a0
> [  251.053700]  [<ffffffff8106c680>] do_page_fault+0x30/0x80
> [  251.077962]  [<ffffffff81003b55>] ? do_syscall_64+0x175/0x180
> [  251.103835]  [<ffffffff8171e208>] page_fault+0x28/0x30
> 
> 
> # kernel versions:
> 
> v4.6 pass in seconds
> v4.7 hang
> v4.9-rc1 hang
> Linus tree to commit 9fe68ca hang
> 
> bisect points to 
>  first bad commit: [ac401cc782429cc8560ce4840b1405d603740917] dax: New fault locking
> 
> v4.7 with these 3 commits reverted pass:
> 4d9a2c8 - Jan Kara, 6 months ago : dax: Remove i_mmap_lock protection
> bc2466e - Jan Kara, 6 months ago : dax: Use radix tree entry lock to protect cow faults
> ac401cc - Jan Kara, 6 months ago : dax: New fault locking
> 
> # nvml version:
> https://github.com/pmem/nvml.git
> to commit:
>   feab4d6f65102139ce460890c898fcad09ce20ae
> 
> # How reproducible:
> always
> 
> # Test steps:
> 
> <git clone and pmem0 setup>
> 
> $cd nvml
> $make install -j64
> 
> $cat > src/test/testconfig.sh <<EOF
> PMEM_FS_DIR=/daxmnt
> NON_PMEM_FS_DIR=/tmp
> EOF
> 
> $mkfs.xfs /dev/pmem0
> $mkdir -p /daxmnt/
> $mount -o dax /dev/pmem0 /daxmnt/
> 
> $make -C src/test/vmmalloc_fork/ TEST_TIME=60m clean
> $make -C src/test/vmmalloc_fork/ TEST_TIME=60m check
> $umount /daxmnt
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR