4 files changed, 66 insertions, 29 deletions
diff --git a/src/libutil/monitor-fd.hh b/src/libutil/monitor-fd.hh
index 6f01ccd91a43..e0ec66c01803 100644
--- a/src/libutil/monitor-fd.hh
+++ b/src/libutil/monitor-fd.hh
@@ -27,8 +27,7 @@ public:
             fds[0].events = 0;
             if (poll(fds, 1, -1) == -1) abort(); // can't happen
             assert(fds[0].revents & POLLHUP);
-            /* We got POLLHUP, so send an INT signal to the main thread. */
-            kill(getpid(), SIGINT);
+            triggerInterrupt();
         });
     };
 
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index f12f02543bc0..5646d08c1314 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -139,6 +139,21 @@ struct StringSource : Source
 };
 
 
+/* Adapter class of a Source that saves all data read to `s'. */
+struct SavingSourceAdapter : Source
+{
+    Source & orig;
+    string s;
+    SavingSourceAdapter(Source & orig) : orig(orig) { }
+    size_t read(unsigned char * data, size_t len)
+    {
+        size_t n = orig.read(data, len);
+        s.append((const char *) data, n);
+        return n;
+    }
+};
+
+
 void writePadding(size_t len, Sink & sink);
 void writeString(const unsigned char * buf, size_t len, Sink & sink);
 
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index e9457582810a..6c4c5c969d86 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -860,6 +860,8 @@ string runProgram(Path program, bool searchPath, const Strings & args,
         Strings args_(args);
         args_.push_front(program);
 
+        restoreSignals();
+
         if (searchPath)
             execvp(program.c_str(), stringsToCharPtrs(args_).data());
         else
@@ -909,16 +911,6 @@ void closeOnExec(int fd)
 }
 
 
-void restoreSIGPIPE()
-{
-    struct sigaction act;
-    act.sa_handler = SIG_DFL;
-    act.sa_flags = 0;
-    sigemptyset(&act.sa_mask);
-    if (sigaction(SIGPIPE, &act, 0)) throw SysError("resetting SIGPIPE");
-}
-
-
 //////////////////////////////////////////////////////////////////////
 
 
@@ -1197,36 +1189,52 @@ static void signalHandlerThread(sigset_t set)
         int signal = 0;
         sigwait(&set, &signal);
 
-        if (signal == SIGINT || signal == SIGTERM || signal == SIGHUP) {
-            _isInterrupted = 1;
-
-            {
-                auto interruptCallbacks(_interruptCallbacks.lock());
-                for (auto & callback : *interruptCallbacks) {
-                    try {
-                        callback();
-                    } catch (...) {
-                        ignoreException();
-                    }
-                }
+        if (signal == SIGINT || signal == SIGTERM || signal == SIGHUP)
+            triggerInterrupt();
+    }
+}
+
+void triggerInterrupt()
+{
+    _isInterrupted = 1;
+
+    {
+        auto interruptCallbacks(_interruptCallbacks.lock());
+        for (auto & callback : *interruptCallbacks) {
+            try {
+                callback();
+            } catch (...) {
+                ignoreException();
             }
         }
     }
 }
 
+static sigset_t savedSignalMask;
+
 void startSignalHandlerThread()
 {
+    if (sigprocmask(SIG_BLOCK, nullptr, &savedSignalMask))
+        throw SysError("quering signal mask");
+
     sigset_t set;
     sigemptyset(&set);
     sigaddset(&set, SIGINT);
     sigaddset(&set, SIGTERM);
     sigaddset(&set, SIGHUP);
+    sigaddset(&set, SIGPIPE);
     if (pthread_sigmask(SIG_BLOCK, &set, nullptr))
         throw SysError("blocking signals");
 
     std::thread(signalHandlerThread, set).detach();
 }
 
+void restoreSignals()
+{
+    if (sigprocmask(SIG_SETMASK, &savedSignalMask, nullptr))
+        throw SysError("restoring signals");
+}
+
 /* RAII helper to automatically deregister a callback. */
 struct InterruptCallbackImpl : InterruptCallback
 {
@@ -1246,7 +1254,7 @@ std::unique_ptr<InterruptCallback> createInterruptCallback(std::function<void()>
     res->it = interruptCallbacks->end();
     res->it--;
 
-    return res;
+    return std::unique_ptr<InterruptCallback>(res.release());
 }
 
 }
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index b68d48582b34..cfaaf1486e9e 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -256,10 +256,6 @@ void closeMostFDs(const set<int> & exceptions);
 /* Set the close-on-exec flag for the given file descriptor. */
 void closeOnExec(int fd);
 
-/* Restore default handling of SIGPIPE, otherwise some programs will
-   randomly say "Broken pipe". */
-void restoreSIGPIPE();
-
 
 /* User interruption. */
 
@@ -423,6 +419,9 @@ void callSuccess(
    on the current thread (and thus any threads created by it). */
 void startSignalHandlerThread();
 
+/* Restore default signal handling. */
+void restoreSignals();
+
 struct InterruptCallback
 {
     virtual ~InterruptCallback() { };
@@ -433,5 +432,21 @@ struct InterruptCallback
 std::unique_ptr<InterruptCallback> createInterruptCallback(
     std::function<void()> callback);
 
+void triggerInterrupt();
+
+/* A RAII class that causes the current thread to receive SIGUSR1 when
+   the signal handler thread receives SIGINT. That is, this allows
+   SIGINT to be multiplexed to multiple threads. */
+struct ReceiveInterrupts
+{
+    pthread_t target;
+    std::unique_ptr<InterruptCallback> callback;
+
+    ReceiveInterrupts()
+        : target(pthread_self())
+        , callback(createInterruptCallback([&]() { pthread_kill(target, SIGUSR1); }))
+    { }
+};
+
 
 }