erts: Make sure fds 0,1 and 2 are open

If they are not open a really nasty race where the io pipe in
erl_poll got fd 0 and the fd_driver setting fd 0 to blocking
could occur. This caused the emulator to hang during shutdown.

1 files changed, 19 insertions, 0 deletions

diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index a7ea4b2490..77d7154313 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -547,6 +547,25 @@ erts_sys_pre_init(void)
 #endif
 #endif /* USE_THREADS */
     erts_smp_atomic_init_nob(&sys_misc_mem_sz, 0);
+
+    {
+      /*
+       * Unfortunately we depend on fd 0,1,2 in the old shell code.
+       * So if for some reason we do not have those open when we start
+       * we have to open them here. Not doing this can cause the emulator
+       * to deadlock when reaping the fd_driver ports :(
+       */
+      int fd;
+      /* Make sure fd 0 is open */
+      if ((fd = open("/dev/null", O_RDONLY)) != 0)
+	close(fd);
+      /* Make sure fds 1 and 2 are open */
+      while (fd < 3) {
+	fd = open("/dev/null", O_WRONLY);
+      }
+      close(fd);
+    }
+
 }
 
 void