mgr: fix deadlock in ActivePyModules::get_osdmap()

[peng-jiaqi]

In function "ActivePyModules::get_osdmap()", We do not read or write to object "ActivePyModules", so it is safe to delete lock "ActivePyModules::lock", and it can avoid other thread waiting for lock "ActivePyModules::lock"

Fixes: https://tracker.ceph.com/issues/48852

Signed-off-by: peng jiaqi peng.jiaqi@zte.com.cn

[tchaikov]

@peng-jiaqi i think this issue has been addressed by 0601b31. could you give it a try?

[peng-jiaqi]

I think my issue and 0601b31 are not the same, In my issue, Thread 39 held lock "Objecter::rwlock" in function "Objecter::handle_osd_map()", and waited on lock "ActivePyModules::lock" in function "ActivePyModules::notify_all()". Thread 30 held lock "ActivePyModules::lock"in function "ActivePyModules::get_osdmap()", and waited on lock "Objecter::rwlock" in function "with_osdmap()". Deadlock occurred in Thread 39 and Thread 30. In 0601b31, Deadlock occurs because of Gil. @tchaikov

[tchaikov]

@peng-jiaqi thanks for the explanation! it makes sense to me. could you please

1. create a tracker ticket at https://tracker.ceph.com. so we can backport this fix,
2. add the backtrace in the tracker ticket as part of its description,
3. outline the deadlock in the commit message instead of dumping the backtrace, and
4. connect this fix to the tracker ticket in the commit message using the notation of Fixes: https://tracker.ceph.com/issues/<id>

?

also, you might want to note down the reason why it's safe to drop the lock in the commit message as well. my guess is that objecter already protects its internal state with the shared lock .

[tchaikov]

@peng-jiaqi ping?

[peng-jiaqi]

I'm back. @tchaikov.

Fixes: https://tracker.ceph.com/issues/48852

In function "ActivePyModules::get_osdmap()", We do not read or write to object "ActivePyModules", so it is safe to delete lock "ActivePyModules::lock", and it can avoid other thread waiting for lock "ActivePyModules::lock"

[tchaikov]

@peng-jiaqi thank you! i added nautilus and octopus to the backport field of the ticket you created.

[tchaikov]

• https://pulpito.ceph.com/kchai-2021-01-14_16:22:32-rados-wip-kefu-testing-2021-01-14-2241-distro-basic-smithi/
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