From 4f09ce7940689887a18d4aa44367d2e6abeaa3cf Mon Sep 17 00:00:00 2001 From: Eelco Dolstra Date: Mon, 12 Feb 2018 16:56:12 +0100 Subject: Fix 'deadlock: trying to re-acquire self-held lock' This was caused by derivations with 'allowSubstitutes = false'. Such derivations will be built locally. However, if there is another SubstitionGoal that has the output of the first derivation in its closure, then the path will be simultaneously built and substituted. There was a check to catch this situation (via pathIsLockedByMe()), but it no longer worked reliably because substitutions are now done in another thread. (Thus the comment 'It can't happen between here and the lockPaths() call below because we're not allowing multi-threading' was no longer valid.) The fix is to handle the path already being locked in both SubstitutionGoal and DerivationGoal. --- src/libstore/build.cc | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) (limited to 'src/libstore/build.cc') diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 392b494e65eb..cc69ff1c74bf 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -1335,19 +1335,6 @@ void DerivationGoal::tryToBuild() { trace("trying to build"); - /* Check for the possibility that some other goal in this process - has locked the output since we checked in haveDerivation(). - (It can't happen between here and the lockPaths() call below - because we're not allowing multi-threading.) If so, put this - goal to sleep until another goal finishes, then try again. */ - for (auto & i : drv->outputs) - if (pathIsLockedByMe(worker.store.toRealPath(i.second.path))) { - debug(format("putting derivation '%1%' to sleep because '%2%' is locked by another goal") - % drvPath % i.second.path); - worker.waitForAnyGoal(shared_from_this()); - return; - } - /* Obtain locks on all output paths. The locks are automatically released when we exit this function or Nix crashes. If we can't acquire the lock, then continue; hopefully some other @@ -3739,6 +3726,17 @@ void SubstitutionGoal::tryToRun() return; } + /* If the store path is already locked (probably by a + DerivationGoal), then put this goal to sleep. Note: we don't + acquire a lock here since that breaks addToStore(), so below we + handle an AlreadyLocked exception from addToStore(). The check + here is just an optimisation to prevent having to redo a + download due to a locked path. */ + if (pathIsLockedByMe(worker.store.toRealPath(storePath))) { + worker.waitForAWhile(shared_from_this()); + return; + } + maintainRunningSubstitutions = std::make_unique>(worker.runningSubstitutions); worker.updateProgress(); @@ -3778,6 +3776,12 @@ void SubstitutionGoal::finished() try { promise.get_future().get(); + } catch (AlreadyLocked & e) { + /* Probably a DerivationGoal is already building this store + path. Sleep for a while and try again. */ + state = &SubstitutionGoal::init; + worker.waitForAWhile(shared_from_this()); + return; } catch (Error & e) { printError(e.msg()); -- cgit 1.4.1