From 46cdc6ad51376e2f31ce806ee38e697d00a6e5cb Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Mon, 30 Apr 2012 10:58:04 -0400 Subject: [PATCH] Handle EPERM when creating a hard link for the chroot There is a race condition when doing parallel builds with chroots and the immutable bit enabled. One process may call makeImmutable() before the other has called link(), in which case link() will fail with EPERM. We could retry or wrap the operation in a lock, but since this condition is rare and I'm lazy, we just use the existing copy fallback. Fixes #9. --- src/libstore/build.cc | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 77e968ddd0..acc2923059 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -1708,8 +1708,11 @@ void DerivationGoal::startBuilder() /* Hard-linking fails if we exceed the maximum link count on a file (e.g. 32000 of ext3), which is quite possible after a `nix-store - --optimise'. Make a copy instead. */ - if (errno != EMLINK) + --optimise'. It can also fail if another + process called makeImmutable() on *i after we + did makeMutable(). In those cases, make a copy + instead. */ + if (errno != EMLINK && errno != EPERM) throw SysError(format("linking `%1%' to `%2%'") % p % *i); StringSink sink; dumpPath(*i, sink);