* Catch SIGINT to terminate cleanly when the user tries to interrupt

  Nix.  This is to prevent Berkeley DB from becoming wedged.

  Unfortunately it is not possible to throw C++ exceptions from a
  signal handler.  In fact, you can't do much of anything except
  change variables of type `volatile sig_atomic_t'.  So we set an
  interrupt flag in the signal handler and check it at various
  strategic locations in the code (by calling checkInterrupt()).
  Since this is unlikely to cover all cases (e.g., (semi-)infinite
  loops), sometimes SIGTERM may now be required to kill Nix.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/libstore/pathlocks.cc b/src/libstore/pathlocks.cc
index 321e965bb34b..d4f980c6487c 100644
--- a/src/libstore/pathlocks.cc
+++ b/src/libstore/pathlocks.cc
@@ -19,11 +19,14 @@ bool lockFile(int fd, LockType lockType, bool wait)
     lock.l_len = 0; /* entire file */
 
     if (wait) {
-        while (fcntl(fd, F_SETLKW, &lock) != 0)
+        while (fcntl(fd, F_SETLKW, &lock) != 0) {
+            checkInterrupt();
             if (errno != EINTR)
                 throw SysError(format("acquiring/releasing lock"));
+        }
     } else {
         while (fcntl(fd, F_SETLK, &lock) != 0) {
+            checkInterrupt();
             if (errno == EACCES || errno == EAGAIN) return false;
             if (errno != EINTR) 
                 throw SysError(format("acquiring/releasing lock"));
@@ -55,6 +58,7 @@ PathLocks::PathLocks(const PathSet & _paths)
     
     /* Acquire the lock for each path. */
     for (Paths::iterator i = paths.begin(); i != paths.end(); i++) {
+        checkInterrupt();
         Path path = *i;
         Path lockPath = path + ".lock";
 
@@ -87,6 +91,7 @@ PathLocks::~PathLocks()
         close(*i);
 
     for (Paths::iterator i = paths.begin(); i != paths.end(); i++) {
+        checkInterrupt();
         if (deletePaths) {
             /* This is not safe in general! */
             unlink(i->c_str());