On Fri, Sep 18, 2020 at 08:20:59AM +0000, IGotD- via Digitalmars-d-learn wrote: > On Friday, 18 September 2020 at 05:02:21 UTC, H. S. Teoh wrote: > > > > That's the obvious solution, except that actually implementing it is not > > so simple. When you have multiple threads listening for each other > > and/or doing work, there is no 100% guaranteed way of cleanly shutting > > all of them down at the same time. You can't just clean up the calling > > thread and leave the others running, because the other threads might > > hold references to your data, etc.. But there's no universal protocol > > for shutting down the other threads too -- they could be in a busy loop > > with some long-running computation, or they may not be checking for > > thread messages, or they could be in a server loop that is designed to > > keep running, etc.. It's one of those annoying things that reduce to > > the halting problem in the general case. [...] > I think a pragmatic solution is just to mutex protect the D exit > function in case several threads tries to use simultaneously. Then if > more threads call exit, it will do nothing as the first one that > called exit actually do the tear down.
That does not solve the problem. If thread 1 calls exit but thread 2 is still running and processing data via a shared reference with thread 1's data, you absolutely do not want to run dtors and tear-down code until thread 2 is done, otherwise you have a problem. OTOH, waiting for thread 2 to finish first comes with its own problems: what if thread 2 never calls exit? Then no cleanup will be done, which may not be desirable either (maybe you had thread 1 call exit because you wanted to release unused resources). > Also, it should be responsibility of the program to ensure that its > tear down code runs before calling the D exit function. That's the > only way I can think of because waiting for all other threads to > release their resources and exit isn't really realistic either as that > might do that the program exit never happens. Whatever you do you, you > have to resort to some "manual" solution". [...] If you're prepared to do manual teardown, then you do not need a D-specific exit function. Just call core.sys.stdc.stdlib.exit and call it a day. :-) T -- Never trust an operating system you don't have source for! -- Martin Schulze
