Example fix #1
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Example fix #1
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apenwarr
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Jan 2, 2019
WSL (Windows Services for Linux) provides a Linux-kernel-compatible ABI for userspace processes, but the current version doesn't not implement fcntl() locks at all; it just always returns success. See microsoft/WSL#1927. This causes us three kinds of problem: 1. sqlite3 in WAL mode gives "OperationalError: locking protocol". 1b. Other sqlite3 journal modes also don't work when used by multiple processes. 2. redo parallelism doesn't work, because we can't prevent the same target from being build several times simultaneously. 3. "redo-log -f" doesn't work, since it can't tell whether the log file it's tailing is "done" or not. To fix #1, we switch the sqlite3 journal back to PERSIST instead of WAL. We originally changed to WAL in commit 5156fea to reduce deadlocks on MacOS. That was never adequately explained, but PERSIST still acts weird on MacOS, so we'll only switch to PERSIST when we detect that locking is definitely broken. Sigh. To (mostly) fix #2, we disable any -j value > 1 when locking is broken. This prevents basic forms of parallelism, but doesn't stop you from re-entrantly starting other instances of redo. To fix that properly, we need to switch to a different locking mechanism entirely, which is tough in python. flock() locks probably work, for example, but python's locks lie and just use fcntl locks for those. To fix #3, we always force --no-log mode when we find that locking is broken.
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Here's a small fix to the inclusion of CFLAGS in the example.
Keep up the good work. I hope redo takes over the world!