Re: [Libguestfs] [PATCH nbdkit] curl: Try to share as much as possible between handles in the pool

On 2/22/23 17:00, Richard W.M. Jones wrote: > On Wed, Feb 22, 2023 at 04:52:35PM +0100, Laszlo Ersek wrote: > ... >> Seems sane to me in general, except for the fact that the documentation >> at <https://curl.se/libcurl/c/CURLSHOPT_SHARE.html> writes: >> >> """ >> CURL_LOCK_DATA_CONNECT >> >> Put the connection cache in the share object and make all easy handles >> using this share object share the connection cache. >> >> Note that due to a known bug, it is not safe to share connections this >> way between multiple concurrent threads. [...] >> """ >> >> Ugh, what? If it's not safe to share the connection cache between >> threads, then CURL_LOCK_DATA_CONNECT is effectively unusable, and no >> connection pooling can be done. How does that *not* make this whole curl >> facility useless? >> >> The facility in general looks super weird; what sense does it make *not* >> to share some particular CURL_LOCK_DATA_xxx? > > I can only conclude this cannot be true. Daniel Stenberg wrote this > code which definitely uses threads: > > https://gist.github.com/bagder/7eccf74f8b6d70b5abefeb7f288dba9b > > Also I did a lot of testing and didn't hit any obvious threading bugs. OK, so the documentation is busted. News at 11. Can you report a bug for cURL, or should I report it sometime later?

> Nevertheless I'm not planning to integrate this patch any time soon. I don't oppose merging the patch once we get a clear verdict that the documentation is wrong. Thanks! Laszlo