If fork flags != 0, share the file table..

..now xdu and xls work in xv6 userspace with the wq stuff..

If fork flags != 0, share the file table..
25641b3a · Silas Boyd-Wickizer · 33750412 · 25641b3a · 25641b3a
--- a/bin/usertests.cc
+++ b/bin/usertests.cc
@@ -1628,6 +1628,41 @@ tls_test(void)
  fprintf(1, "tls_test ok\n");
 }
+static pthread_barrier_t ftable_bar;
+static volatile int ftable_fd;
+static void*
+ftablethr(void *arg)
+{
+  char buf[32];
+  int r;
+  pthread_barrier_wait(&ftable_bar);
+  r = read(ftable_fd, buf, sizeof(buf));
+  if (r < 0)
+    fprintf(2, "ftablethr: FAILED bad fd\n");
+  return 0;
+}
+static void
+ftabletest(void)
+{
+  printf("ftabletest...\n");
+  pthread_barrier_init(&ftable_bar, 0, 2);
+  pthread_t th;
+  pthread_create(&th, 0, &ftablethr, 0);
+  ftable_fd = open("README", 0);
+  if (ftable_fd < 0)
+    die("open");
+  pthread_barrier_wait(&ftable_bar);
+  wait();
+  printf("ftabletest ok\n");
+}
 static pthread_key_t tkey;
 static pthread_barrier_t bar0, bar1;
 enum { nthread = 8 };
@@ -1718,6 +1753,7 @@ main(int argc, char *argv[])
  bigdir(); // slow
  tls_test();
  thrtest();
+  ftabletest();
  exectest();

--- a/kernel/proc.cc
+++ b/kernel/proc.cc
@@ -460,12 +460,17 @@ fork(int flags)
  // Clear %eax so that fork returns 0 in the child.
  np->tf->rax = 0;
+  if (flags == 0) {
    np->ftable = new filetable(*myproc()->ftable);
    if (np->ftable == nullptr) {
      // XXX(sbw) leaking?
      freeproc(np);
      return -1;
    }
+  } else {
+    myproc()->ftable->incref();
+    np->ftable = myproc()->ftable;
+  }
  np->cwd = idup(myproc()->cwd);
  pid = np->pid;