Fix #13217; this is an alternative to #13674
Fix #17495

As a side effect, this PR makes bitcoin-qt shutdown routine more streamlined.

Refs:

• GUI unresponsive during slow operations #10504
• GUI event loop should be block free #17145

Could you update this with a description of what this PR does? Useful information to include:

• details about how behavior changed, what behavior was before and after this change
• a short description of the code changes, what was wrong with the old code, and how the commits relate to each other
• how this compares to the alternative pr

It's great to link to other issues and pull requests in a PR description for extra details, but it shouldn't be necessary to open multiple other issues just to have a basic understanding of what a PR does and what motivated it

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Conflicts

No conflicts as of last run.

Calling waitfornewblock in the GUI console returns immediately.

Calling waitfornewblock in the GUI console returns immediately.

I have observed such behavior on regtest only once, and cannot reproduce anymore.

Could you provide steps to reproduce an issue reliably?

@ryanofsky

OP has been updated.

@hebasto actually it's unrelated to this change. Just noticed that waitfornewblock returns immediately in the GUI console because IsRPCRunning is false unless you start with -server.

The folllowing still hangs:

• bitcoin-qt -regtest -server
• open gui console
• run waitfornewblock
• try to quit

Are you able to reproduce?

@promag

The folllowing still hangs:

* `bitcoin-qt -regtest -server`

* open gui console

* run `waitfornewblock`

* try to quit

This requires a forced interruption of the RPC thread. It seems a bit out of the scope of this PR, as it solves the blocking of the GUI thread only.

In your example bitcoin-qt literally "waits for new block", which is unreachable in regtest after quit is initiated ;)
But this PR works on mainnet and testnet: bitcoin-qt quits just after a new block arrives.

Maybe, to mention in OP that #17495 is fixed, is wrong, no?

@hebasto maybe just mention it's not a complete fix.

@promag

@hebasto maybe just mention it's not a complete fix.

The mention about the fix of #17495 has been removed from PR description.

The actual fix of #17495 is #18452 ;)

Rebased 485e3de -> e7ee445 (pr17659.01 -> pr17659.02) due to the conflict with #16224.

Nice. Concept ACK

Concept ACK. Needs rebase.

Rebased e7ee445 -> 776d157 (pr17659.02 -> pr17659.03) due to the conflict with #16432.

Rebased 776d157 -> 47912c5 (pr17659.03 -> pr17659.04) due to the conflict with #19011.

Lets move this over to the GUI repo. I've also ported the original issue there now as well, given that the non-gui part has been fixed.

Moved to bitcoin-core/gui#59.