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clang failing due to header not found, filesystem race condition
I'm seeing an intermittent issue where occasionally clang fails due to a header file not being found. However, I login to the machine and can see the header file there in buck-out. It seems like some kind of race condition where buck sets up the symlink for the header but that operation doesn't finish before buck runs clang which depends on that header.
Has anyone seen something like this? Building on a fairly standard macpro setup with APFS filesystem with disk mount properties (apfs, local, journaled).
This is related to the number of worker threads. On a macpro with 24 virtual cores: with 24 threads, the error happens very frequently (probably 20% of the time). I tried 20 and there was a slight improvement. With 12 threads, the error occurs a lot more rarely (but is still present, probably about 3% of builds hit it).
