I've been running 7.72.0 with that patch cherry-picked for over a day and the issue has not recurred. There's definitely something spooky going on. Does extract_if_dead have any other side effects?
On Wed, Sep 16, 2020 at 1:22 AM Daniel Stenberg <dan...@haxx.se> wrote: > On Mon, 14 Sep 2020, James Brown via curl-library wrote: > > Thanks for digging deep into this issue! > > > I went through commits on master that aren't in 7.72.0 and came across > > 728f8d3bd > > < > https://github.com/curl/curl/commit/728f8d3bdc336e3fa838f45cad6c0133a6b604ae>, > > > which looks promising. It says it partially reverts a change from > 7.65.2, > > which is kind of weird because this problem does *not *occur for me in > > 7.71.1, which suggests that one of the other changes in 7.72.0 (maybe > the > > schannel stuff?) somehow had some spooky-action-at-a-distance and made > this > > much worse in 7.72.0. > > Well, the problem this commit fixes is the opposite: libcurl would > previously > reuse connections that actually are already dead and thus detecting the > "deadness" gets delayed. > > > I feel like 728f8d3bd still has a race condition if the FIN has been > issued > > by the server but not yet processed by poll, but that's neither here nor > > there. > > It's a race, sure, but that shouldn't be a problem. If the connection is > dead > at the time extract_if_dead() is called, it should detect that and not > reuse > the connection. > > If it dies a millisecond after the check, the connection will instead be > reused and the sending of the outgoing request will subsequently fail. > libcurl > will then attempt to create a new connection and retry the request over > that. > > If indeed calling extract_if_dead() there causes the problem for you, then > I'd > like to get more information about what exactly the problem is within that > function so that we can address that rather than just reverting the commit > again and just go full yoyo on these issues! > > -- > > / daniel.haxx.se | Commercial curl support up to 24x7 is available! > | Private help, bug fixes, support, ports, new features > | https://www.wolfssl.com/contact/ > -- James Brown Engineer
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