+1 Javier On Thu, 12 Sept 2024 at 08:27, Rahkonen Jukka via gdal-dev < gdal-dev@lists.osgeo.org> wrote:
> +1 > > -Jukka Rahkonen- > > -----Alkuperäinen viesti----- > Lähettäjä: gdal-dev <gdal-dev-boun...@lists.osgeo.org> Puolesta Even > Rouault via gdal-dev > Lähetetty: keskiviikko 11. syyskuuta 2024 22.27 > Vastaanottaja: gdal-dev@lists.osgeo.org > Aihe: [gdal-dev] Motion: approve RFC 101 "Raster dataset read-only > thread-safety" > > Hi, > > I move to approve RFC 101 "Raster dataset read-only thread-safety": > https://github.com/OSGeo/gdal/pull/10676 > > Starting with my +1, > > The candidate implementation is available in > https://github.com/OSGeo/gdal/pull/10746. While fine tuning it, I > realized there were subtleties, related to the fact we use thread-local > datasets under the hood, for methods returning a non-"primitive" type, such > as a "const char*" whose lifetime is tied to a dataset/band. If we'd get it > from a thread-local dataset, and that one would be later evicted from the > cache (not very common, but could happen if one would open tons of > thread-safe datasets at the same time), then you could have use-after-free > issues. For such methods (GetMetadata(), GetMetadataItem(), > GetProjectionRef(), etc. as well as GetColorTable() which returns a > GDALColorTable pointer, or GetSpatialRef() which returns a > OGRSpatialReference*), I've preferred to protect their access with a mutex > around the "prototype" dataset passed when constructing > GDALMultiThreadedDataset, whose lifetime is at least as long as > GDALMultiThreadedDataset (cf commit > > https://github.com/OSGeo/gdal/pull/10746/commits/849e9cea711efd30c47fd90a7a6b71a75611c1a5#diff-687008dd6e3d5ac8ad05568272746ed75b84de50bde508f78f2d79a6842825c7L428 > ) > . Normally such methods aren't called in user code repeatedly, so there > should be any noticeable lock contention in practice. The main objective of > the RFC which is to be able to issue RasterIO() requests in parallel isn't > affected by that. Ah, and one thing I realized is that OGRSpatialReference > isn't thread-safe, so I've also added an optional > SetThreadSafe() on it, to also use a per-instance mutex in multi-threaded > scenarios (cf commit > https://github.com/OSGeo/gdal/pull/10746/commits/c7e1862273dd018e58a01f25b21fdff6dbfdd1cd > ). > Multi-threading is hard... > > Even > > -- > http://www.spatialys.com/ > My software is free, but my time generally not. > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > https://lists.osgeo.org/mailman/listinfo/gdal-dev >
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