On Wed, Jun 30, 2021 at 10:09 AM www <ouyangxuan10@xxxxxxx> wrote:
Dear all,systemd version: v234kernel version: 5.1.5My embedded system uses systemd. Occasionally kernel panic appears in this system. It is found that it is related to sd-sync in systemd. How to analyze this and why?
What causes this problem? Or can you see that sd-sync has a problem processing that file or service?If you have any ideas or opinions, or need any specific information, please let me know.Thank you.[ 1664.582102] Unable to handle kernel paging request at virtual address 7f8bba1c
[ 1664.589350] pgd = fb46e47e
[ 1664.592062] [7f8bba1c] *pgd=00000000
[ 1664.595666] Internal error: Oops: 80000005 [#1] ARM
[ 1664.600558] CPU: 0 PID: 14730 Comm: (sd-sync) Not tainted 5.1.5-yocto-s-dirty-fd96c2b #1
When shutdown.target is invoked, systemd forks a 'sd-sync' background process which does literally one thing: it issues a global sync() to begin flushing all filesystems to disk. There is no specific file involved here, sync() handles all mounted filesystems at once.
Check what happens if you run `/usr/sbin/sync` from shell, since it does exactly the same thing. In general there should be nothing special about systemd calling sync(), it's purely a kernel problem. The only difference that I can think of is that systemd begins the sync() while all services are shutting down and still actively writing to files...
Mantas Mikulėnas
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