[Bugfix] Revert "[Bugfix] use SoftLockFile instead of LockFile (#3578)"

[WoosukKwon]

Reverts #3578 for backward compatibility.

[kota-iizuka]

@WoosukKwon Please use lockfile.Lockfile(mode=666) to fix bugs with multi-user usage. #3578 (comment)

[youkaichao]

Let me send a fix.

[youkaichao]

@kota-iizuka can you test if this branch works as you want now?

[kota-iizuka]

can you test if this branch works as you want now?

@youkaichao I did an experiment, but contrary to expectations I got the same permission denied error. I'll look into the method a little more

[kota-iizuka]

I'll look into the method a little more

This modification in vLLM is OK for me.

I found the bug is in filelock. https://github.com/tox-dev/filelock/blob/main/src/filelock/_unix.py#L38 uses os.O_CREAT, so if a file already created by another user exists, It will be the permission error.

[youkaichao]

If multiple users use one server together, they should have their own directory for storing models.

This modification in vLLM is OK for me.

Then I will merge it now.