On 7/4/25 3:10 PM, Eelco Chaudron wrote: > > > On 30 Jun 2025, at 13:21, Ilya Maximets wrote: > >> There is an ABBA deadlock between time_init() and seq_wait(): >> >> Thread 1: >> poll_block() >> time_poll() >> time_init() >> pthread_once() <-- lock A >> do_time_init() >> seq_create() >> pthread_mutex_lock(seq_mutex) <-- lock B >> >> Thread 2: >> seq_wait(different seqno) >> pthread_mutex_lock(seq_mutex) <-- lock B >> poll_immediate_wake() >> poll_timer_wait() >> time_msec() >> time_init() >> pthread_once() <-- lock A >> >> This is likely the same deadlock Intel CI saw last year before the lab >> was shut down. >> >> The issue should not happen with normal applications as those would >> normally have the time module initialized early in the process before >> waiting on any sequence numbers, but it happens in the test-barrier >> application from time to time causing the test suite to hang. >> >> Fix that by making sure we're not calling poll_immediate_wake() under >> the seq_mutex. The time and seq modules are independent and it's hard >> to ensure the dependency without exporting some of their internals. >> Instead re-defining the prototype of the poll_immediate_wake_at(), >> adding the thread safety annotation, so we have some basic protection >> from this deadlock if the code ever changes. Compiler will warn on >> the prototype mismatch as well if it ever happens, so it's not a big >> problem. Having this prototype also gives us a spot in the code where >> we can place a comment explaining the locking order. >> >> Reportde-at: >> https://mail.openvswitch.org/pipermail/ovs-dev/2024-July/415436.html >> Reported-at: https://issues.redhat.com/browse/FDP-1493 >> Signed-off-by: Ilya Maximets <i.maxim...@ovn.org> > > Thanks, Ilya, for getting to the bottom of this. The change looks good to me. > > Acked-by: Eelco Chaudron <echau...@redhat.com> >
Thanks! Applied and backported down to 3.2. Best regards, Ilya Maximets. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
