PreparedGeometry::contains is not thread safe

[gauteh]

Hi,

It seems that prepared geometry contains is not thread safe before run at least once. Easiest to provoke on large geometries. Not able to provoke on example in docs.

Regards, Gaute

[GuillaumeGomez]

Can you provide me a code having this issue so I can fix it and enforce it through tests please?

[gauteh]

https://github.com/gauteh/roaring-landmask/pull/6/files#diff-6423871468d8d2f4ebf2a85e879f9ba388c361b859c9191d62d4571685c95f58 , I think you need a big geometry for this to trigger.

[GuillaumeGomez]

Ok, I'll try to take a look when I have a bit of time.

[gauteh]

👍 thanks. I can work around this atm by using a warmup call. It is most likely an upstream bug. But would be a pity to !Send/!Sync Geometry/PreparedGeometry just because of that.

[GuillaumeGomez]

Don't hesitate to take a look in the meantime. If yu can find a way to go around this limitation without removing Send and Sync, it'd be perfect. :)

[gauteh]

If we can afford a warmup call to `contains`, that is the only way I can think of at the moment (without fixing upstream). From the backtrace in geos it seems like the segfault happens somewhere in sorting of a vector in the geometry. I'll take a further look if(/when..?) I find the time!

…

On Wed, Sep 8, 2021 at 8:33 PM Guillaume Gomez ***@***.***> wrote: Don't hesitate to take a look in the meantime. If yu can find a way to go around this limitation without removing Send and Sync, it'd be perfect. :) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#95 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAN364WETWQORRMMUE24X3UA6UALANCNFSM5DUZS3CA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[GuillaumeGomez]

Thanks, greatly appreciated! A bit under the water currently. ^^'

[gauteh]

No problem, thanks for the effort!

[gauteh]

In version 9 with geos 3.11 it is no longer reliable to warm up the prepared geometry to make it thread safe.

[gauteh]

This is still the case, I don't know how to fix this. PreparedGeometry is not thread-safe.

This test fails: https://github.com/gauteh/roaring-landmask/blob/main/src/lib.rs#L328
While this is ok: https://github.com/gauteh/roaring-landmask/blob/main/src/lib.rs#L283

In https://github.com/gauteh/roaring-landmask/blob/geos311/src/shapes.rs the unsafe is removed, and the test is still failing.

[gauteh]

Maybe related:

• Make prepared geometry (more?) thread-safe libgeos/geos#826
• Prepared geometry is not thread-safe libgeos/geos#825