[dm-devel] [PATCH -next v2 4/6] md: refactor idle/frozen_sync_thread() to fix deadlock

[Yu Kuai]

Hi,

在 2023/06/14 9:48, Yu Kuai 写道:


>>
>> In the patch, sync_seq is added in md_reap_sync_thread. In 
>> idle_sync_thread, if sync_seq isn't equal
>>
>> mddev->sync_seq, it should mean there is someone that stops the sync 
>> thread already, right? Why do
>>
>> you say 'new started sync thread' here?

If someone stops the sync thread, and new sync thread is not started,
then this sync_seq won't make a difference, above wait_event() will not
wait because !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) will pass.
So 'sync_seq' is only used when the old sync thread stops and new sync
thread starts, add 'sync_seq' will bypass this case.

Thanks,
Kuai