On Fri, Aug 06, 2021 at 05:03:44PM +0900, Byungchul Park wrote: > Hello crypto folks, > > I developed a tool for tracking waiters and reporting if any of the > events that the waiters are waiting for would never happen, say, a > deadlock. Yes, it would look like Lockdep but more inclusive. > > While I ran the tool(Dept: Dependency Tracker) on v5.4.96, I got some > reports from the tool. One of them is related to crypto subsystem. > Because I'm not that familiar with the code, I'd like to ask you guys to > review the related code. > > If I understand correctly, it doesn't actually cause deadlock but looks > like a problematic code. I know you are not used to the format of the > report from Dept so.. let me summerize the result. > > The simplified call trace looks like when the problem araised : > > THREAD A > -------- > A1 crypto_alg_mod_lookup() > A2 crypto_probing_notify(CRYPTO_MSG_ALG_REQUEST) > A3 cryptomgr_schedule_probe() > A4 kthread_run(cyptomgr_probe) ---> Start THREAD B > > A5 crypto_larval_wait() > A6 wait_for_completion_killable_timeout(c) /* waiting for B10 */ This larval would be an instantiation larval, and it can only be woken up by thread B, not C. > THREAD B > -------- > B1 cryptomgr_probe() > B2 pkcslpad_create() > B3 crypto_wait_for_test() > B4 crypto_probing_notify(CRYPTO_MSG_ALG_REGISTER) > B5 cryptomgr_schedule_test() > B6 kthread_run(cyptomgr_test) ---> Start THREAD C > > B7 tmpl->alloc() > B8 crupto_register_instance() > B9 wait_for_completion_killable(c) /* waiting for C3 */ > B10 complete_all(c) I presume you're talking about about the wait_for_completion from crypto_wait_for_test, in which case it can only be woken by thread C. After which thread B will return to cryptomgr_probe and wake up thread A. > THREAD C > -------- > C1 cryptomgr_test() > C2 crypto_alg_tested() > C3 complete_all(c) > > --- > > For example, in this situation, I think C3 could wake up both A6 and B9 > before THREAD B reaches B10 which is not desired by A6. Say, is it okay > to wake up A6 with B7 ~ B9 having yet to complete? AFAICS thread C only wakes up test larvals, not instantiation larvals. Please let me know if you have any further issues. Thanks, -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
