regtest: setgenerate true assert failure

[wtogami]

If you run setgenerate true too rapidly in regtest mode, bitcoind can crash with

/home/ubuntu/install/include/boost/thread/pthread/condition_variable_fwd.hpp:81: boost::condition_variable::~condition_variable(): Assertion `!ret' failed.

This was reproduced with the Linux 64bit gitian binary.

[wtogami]

Sometimes it kills bitcoind without a visible asert failure. Sometimes bitcoind just misses the RPC entirely without any visible error and without killing bitcoind.

[laanwj]

Setgenerate is marked as 'threadSafe' in the vRPCCommands table. This means that a potential race can happen if it is not really thread-safe.
You could try setting threadSafe to false (which will make it acquire all locks beforehand) to see if that fixes the issue.

[laanwj]

This is resolved by now. Don't use setgenerate on regtest, use generate.