fix: Prevent Interrupted from falling out of a thread

... into std::terminate; a crash.

This also adds `checkInterrupt` calls to speed up shutdowns.

src/libstore/unix/build/local-derivation-goal.cc

@@ -19,6 +19,7 @@
 #include "unix-domain-socket.hh"
 #include "posix-fs-canonicalise.hh"
 #include "posix-source-accessor.hh"
+#include "signals.hh"
 
 #include <regex>
 #include <queue>
@@ -1504,7 +1505,7 @@ void LocalDerivationGoal::startDaemon()
 
     daemonThread = std::thread([this, store]() {
 
-        while (true) {
+        loopUntilInterrupted([this, store]() {
 
             /* Accept a connection. */
             struct sockaddr_un remoteAddr;
@@ -1513,8 +1514,8 @@ void LocalDerivationGoal::startDaemon()
             AutoCloseFD remote = accept(daemonSocket.get(),
                 (struct sockaddr *) &remoteAddr, &remoteAddrLen);
             if (!remote) {
-                if (errno == EINTR || errno == EAGAIN) continue;
-                if (errno == EINVAL || errno == ECONNABORTED) break;
+                if (errno == EINTR || errno == EAGAIN) return Continue;
+                if (errno == EINVAL || errno == ECONNABORTED) return Stop;
                 throw SysError("accepting connection");
             }
 
@@ -1536,8 +1537,8 @@ void LocalDerivationGoal::startDaemon()
             });
 
             daemonWorkerThreads.push_back(std::move(workerThread));
-        }
-
+        });
+        // We've been interrupted, so we shut down this thread asap.
         debug("daemon shutting down");
     });
 }

src/libutil/thread-pool.cc

@@ -89,7 +89,7 @@ void ThreadPool::doWork(bool mainThread)
     bool didWork = false;
     std::exception_ptr exc;
 
-    while (true) {
+    loopUntilInterrupted([&]() {
         work_t w;
         {
             auto state(state_.lock());
@@ -122,7 +122,7 @@ void ThreadPool::doWork(bool mainThread)
             /* Wait until a work item is available or we're asked to
                quit. */
             while (true) {
-                if (quit) return;
+                if (quit) return Stop;
 
                 if (!state->pending.empty()) break;
 
@@ -132,7 +132,7 @@ void ThreadPool::doWork(bool mainThread)
                 if (!state->active && state->draining) {
                     quit = true;
                     work.notify_all();
-                    return;
+                    return Stop;
                 }
 
                 state.wait(work);
@@ -150,7 +150,10 @@ void ThreadPool::doWork(bool mainThread)
         }
 
         didWork = true;
-    }
+        return Continue;
+    });
+    // We've been interrupted or there's no more work to do; either way we
+    // must return now.
 }
 
 }