In the Linux kernel, the following vulnerability has been resolved:
md: Dont register sync_thread for reshape directly
Currently, if reshape is interrupted, then reassemble the array will register sync_thread directly from pers->run(), in this case MD_RECOVERY_RUNNING is set directly, however, there is no guarantee that md_do_sync() will be executed, hence stop_sync_thread() will hang because MD_RECOVERY_RUNNING cant be cleared.
Last patch make sure that md_do_sync() will set MD_RECOVERY_DONE, however, following hang can still be triggered by dm-raid test shell/lvconvert-raid-reshape.sh occasionally:
[root@fedora ~]# cat /proc/1982/stack [<0>] stop_sync_thread+0x1ab/0x270 [md_mod] [<0>] md_frozen_sync_thread+0x5c/0xa0 [md_mod] [<0>] raid_presuspend+0x1e/0x70 [dm_raid] [<0>] dm_table_presuspend_targets+0x40/0xb0 [dm_mod] [<0>] __dm_destroy+0x2a5/0x310 [dm_mod] [<0>] dm_destroy+0x16/0x30 [dm_mod] [<0>] dev_remove+0x165/0x290 [dm_mod] [<0>] ctl_ioctl+0x4bb/0x7b0 [dm_mod] [<0>] dm_ctl_ioctl+0x11/0x20 [dm_mod] [<0>] vfs_ioctl+0x21/0x60 [<0>] __x64_sys_ioctl+0xb9/0xe0 [<0>] do_syscall_64+0xc6/0x230 [<0>] entry_SYSCALL_64_after_hwframe+0x6c/0x74
Meanwhile mddev->recovery is: MD_RECOVERY_RUNNING | MD_RECOVERY_INTR | MD_RECOVERY_RESHAPE | MD_RECOVERY_FROZEN
Fix this problem by remove the code to register sync_thread directly from raid10 and raid5. And let md_check_recovery() to register sync_thread.