The ParentCache doesn't seem to be generated correctly in circleci

[qy3u]

Hi @cryptonemo @dignifiedquire . I just saw the CI test failure on my previous PR #1477 .

After checking the detail of the failure in https://circleci.com/api/v1.1/project/github/filecoin-project/rust-fil-proofs/74927/output/106/0?file=true&allocation-id=611544a9648d5f76edbe1b19-0-build%2F7693C729
I found the error message: 'Error: corrupted cache: /var/tmp/filecoin-parents/v28-sdr-parent-3f0eef38bb48af1f48ad65e14eb85b4ebfc167cec18cd81764f6d998836c9899.cache, expected at least 3584, got 0 bytes'

According to the message, it seems that the test failed because the ParentCache file doesn't generated correctly(or flush to disk) in circleci. Besides,I have checkout to the commit that contains my PR and run the test locally, here is my command: FIL_PROOFS_USE_MULTICORE_SDR=1 RUST_LOG=trace cargo test lifecycle_2kib --no-default-features --features gpu,blst --verbose --package filecoin-proofs --release -- --ignored --nocapture . The test passed on my ubuntu machine.

I don't know a lot about circleci.I don't know in what environment it run these tests, but I saw it generate '/var/tmp/filecoin-parents/v28-sdr-parent-3f0eef38bb48af1f48ad65e14eb85b4ebfc167cec18cd81764f6d998836c9899.cache' and other cache multi times. In my sense, It's a little weired because while generating the cache, It use an exclusive file lock:

rust-fil-proofs/storage-proofs-porep/src/stacked/vanilla/cache.rs

Line 298 in 9d6da0d

with_exclusive_lock(&path.to_path_buf(), |file| {

According to the implemention of the LockFile, it use create_new not create

rust-fil-proofs/storage-proofs-core/src/parameter_cache.rs

Lines 102 to 112 in 9d6da0d

	pub fn open_exclusive<P: AsRef<Path>>(p: P) -> io::Result<Self> {
	let f = OpenOptions::new()
	.read(true)
	.write(true)
	.create_new(true)
	.open(p)?;
	f.lock_exclusive()?;
	Ok(LockedFile(f))
	}

create_new will failed if the file exists.So, it makes me a little confused that how can these tests passed while multiple generating onto the same path exist (for example generating /var/tmp/filecoin-parents/v28-sdr-parent-b43672d2166d241418debd08d351335b3aa264f729125470f2eeb68f7a11fb20.cache appear 3 times on the log above)? Looking forward to your opinion!

[cryptonemo]

Resolved by #1496