From 81c3f99b3668a1ea6a37792a5bcc3bc6f39729a2 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Na=C3=AFm=20Favier?= Date: Sat, 17 Dec 2022 18:31:00 +0100 Subject: [PATCH] Release shared lock before acquiring exclusive lock In principle, this should avoid deadlocks where two instances of Nix are holding a shared lock on big-lock and are both waiting to get an exclusive lock. However, it seems like `flock(2)` is supposed to do this automatically, so it's not clear whether this is actually where the problem comes from. --- src/libstore/local-store.cc | 2 ++ 1 file changed, 2 insertions(+) diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc index b67668e52..3bab10af9 100644 --- a/src/libstore/local-store.cc +++ b/src/libstore/local-store.cc @@ -91,6 +91,7 @@ void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd) if (!lockFile(lockFd.get(), ltWrite, false)) { printInfo("waiting for exclusive access to the Nix store for ca drvs..."); + lockFile(lockFd.get(), ltNone, false); // We have acquired a shared lock; release it to prevent deadlocks lockFile(lockFd.get(), ltWrite, true); } @@ -299,6 +300,7 @@ LocalStore::LocalStore(const Params & params) if (!lockFile(globalLock.get(), ltWrite, false)) { printInfo("waiting for exclusive access to the Nix store..."); + lockFile(globalLock.get(), ltNone, false); // We have acquired a shared lock; release it to prevent deadlocks lockFile(globalLock.get(), ltWrite, true); }