On Wed, Aug 23, 2023 at 07:30:47AM +0000, Lu Jialin wrote: > We found a hungtask bug in test_aead_vec_cfg as follows: > > INFO: task cryptomgr_test:391009 blocked for more than 120 seconds. > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > Call trace: > __switch_to+0x98/0xe0 > __schedule+0x6c4/0xf40 > schedule+0xd8/0x1b4 > schedule_timeout+0x474/0x560 > wait_for_common+0x368/0x4e0 > wait_for_completion+0x20/0x30 > test_aead_vec_cfg+0xab4/0xd50 > test_aead+0x144/0x1f0 > alg_test_aead+0xd8/0x1e0 > alg_test+0x634/0x890 > cryptomgr_test+0x40/0x70 > kthread+0x1e0/0x220 > ret_from_fork+0x10/0x18 > Kernel panic - not syncing: hung_task: blocked tasks > > For padata_do_parallel, when the return err is 0 or -EBUSY, it will call > wait_for_completion(&wait->completion) in test_aead_vec_cfg. In normal > case, aead_request_complete() will be called in pcrypt_aead_serial and the > return err is 0 for padata_do_parallel. But, when pinst->flags is > PADATA_RESET, the return err is -EBUSY for padata_do_parallel, and it > won't call aead_request_complete(). Therefore, test_aead_vec_cfg will > hung at wait_for_completion(&wait->completion), which will cause > hungtask. > > The problem comes as following: > (padata_do_parallel) | > rcu_read_lock_bh(); | > err = -EINVAL; | (padata_replace) > | pinst->flags |= PADATA_RESET; > err = -EBUSY | > if (pinst->flags & PADATA_RESET) | > rcu_read_unlock_bh() | > return err > > In order to resolve the problem, we retry at most 5 times when > padata_do_parallel return -EBUSY. For more than 5 times, we replace the > return err -EBUSY with -EAGAIN, which means parallel_data is changing, and > the caller should call it again. Steffen, should we retry this at all? Or should it just fail as it did before? Thanks, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
