fix(tvix): Make working flag thread_local r/1782

Since the daemon is running in threads now rather than forking a process
per connection (thanks to grpc) this static flag to prevent accidentally
initializing a new worker during a build is getting stepped on by
multiple threads. This converts it to thread-local, and also adds an
actual message to the check so that if it hits in the future we know
what's going on.

Fixes: b/58
Change-Id: I07a2f1582e56709c104f79935e5405fa24888f59
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1940
Tested-by: BuildkiteCI
Reviewed-by: kanepyork <rikingcoding@gmail.com>
Reviewed-by: V <v@anomalous.eu>

1 files changed, 4 insertions, 5 deletions

diff --git a/third_party/nix/src/libstore/build.cc b/third_party/nix/src/libstore/build.cc
index 502281d0051c..a009651c9d96 100644
--- a/third_party/nix/src/libstore/build.cc
+++ b/third_party/nix/src/libstore/build.cc
@@ -4241,14 +4241,13 @@ void SubstitutionGoal::handleEOF(int fd) {
 
 //////////////////////////////////////////////////////////////////////
 
-static bool working = false;
+ABSL_CONST_INIT static thread_local bool working = false;
 
 Worker::Worker(LocalStore& store, std::ostream& log_sink)
     : log_sink_(log_sink), store(store) {
-  /* Debugging: prevent recursive workers. */
-  if (working) {
-    abort();
-  }
+  // Debugging: prevent recursive workers.
+  // TODO(grfn): Do we need this?
+  CHECK(!working) << "Worker initialized during execution of a worker";
   working = true;
   nrLocalBuilds = 0;
   lastWokenUp = steady_time_point::min();