On 8/23/23 03:28, Yu Kuai wrote:
Hi,
在 2023/08/23 3:13, Carlos Carvalho 写道:
Song Liu (song@xxxxxxxxxx) wrote on Tue, Aug 22, 2023 at 03:56:04PM -03:
>From systemd code, i.e. function delete_md(), this error:
[ 205.957004] systemd-shutdown[1]: Stopping MD /dev/md124p1 (259:6).
[ 205.964177] systemd-shutdown[1]: Could not stop MD /dev/md124p1:
Device or resource busy
is most likely triggered by ioctl(STOP_ARRAY).
And based on the code, I think the ioctl fails here:
if (cmd == STOP_ARRAY || cmd == STOP_ARRAY_RO) {
/* Need to flush page cache, and ensure no-one else
opens
* and writes
*/
mutex_lock(&mddev->open_mutex);
if (mddev->pers && atomic_read(&mddev->openers) > 1) {
mutex_unlock(&mddev->open_mutex);
err = -EBUSY;
goto out; ////////////////////// HERE
Yes, I suspect here as well, but I do some test with error injection to
gurantee that ioctl(STOP_ARRAY) always return -EBUSY, but I found that
system reboot didn't hang, it'll try a few times but eventually reboot
finished.
}
if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
mutex_unlock(&mddev->open_mutex);
err = -EBUSY;
goto out;
}
did_set_md_closing = true;
mutex_unlock(&mddev->open_mutex);
sync_blockdev(bdev);
}
Probably. The problem is why doesn't it manage to flush the page
cache? I find
strange that the problem appears only when trying to stop the array, I
get it
when trying to umount the filesystem, where it also hangs because of
the same
reason. The kworker thread runs continuously using 100% cpu of only 1
core.
The kworker do you mean the daemon thread or the sync thread? runs
continuously using 100% cpu doen't sounds correct to me.
That sounds more like kworker waiting on a mutex to be released.
Can you trigger a kdump while in that state?
Or do a sysrq-T to get a stack trace of all running processes?
That should tell you where exactly the 100% cpu time is being
wasted.
Cheers,
Hannes
--
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