[Bug 1905651] Re: Tests cannot call g_error

[Doug Evans <1905651@bugs.launchpad.net>]

I don't know QEMU that well yet, but the following question arises: Why
can't QEMU be driven in a way that allows it to see that its controlling
parent has died -> causing QEMU to terminate as well. That way the test
doesn't need to care how it dies (e.g., we don't want a segfault to hang
testing; and nor do we, I think, want to install signal handlers for
every possible signal).

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https://bugs.launchpad.net/bugs/1905651

Title:
  Tests cannot call g_error

Status in QEMU:
  New

Bug description:
  I stumbled on this writing a new test, using tests/qtest/e1000e-test.c
  as a template.

  g_error() causes SIGTRAP, not SIGABRT, and thus the abort handler doesn't get run.
  This in turn means qemu is not killed, which hangs the test because the tap-driver.pl script hangs waiting for more input.
  There are a few tests that call g_error().

  The SIGABRT handler explicitly kills qemu, e.g.:

  qos-test.c:
      qtest_add_abrt_handler(kill_qemu_hook_func, s);

  ref:
  https://git.qemu.org/?p=qemu.git;a=blob;f=tests/qtest/libqtest.c;h=e49f3a1e45f4cd96279241fdb2bbe231029ab922;hb=HEAD#l272

  But not unexpectedly there's no such handler for SIGTRAP.

  Apply this patch to trigger a repro:

  diff --git a/tests/qtest/e1000e-test.c b/tests/qtest/e1000e-test.c
  index fc226fdfeb..e83ace1b5c 100644
  --- a/tests/qtest/e1000e-test.c
  +++ b/tests/qtest/e1000e-test.c
  @@ -87,6 +87,9 @@ static void e1000e_send_verify(QE1000E *d, int *test_sockets, QGuestAllocator *a
       /* Wait for TX WB interrupt */
       e1000e_wait_isr(d, E1000E_TX0_MSG_ID);

  +    g_message("Test g_error hang ...");
  +    g_error("Pretend something timed out");
  +
       /* Check DD bit */
       g_assert_cmphex(le32_to_cpu(descr.upper.data) & dsta_dd, ==, dsta_dd);

  Then:

  configure
  make
  make check-qtest-i386

  check-qtest-i386 will take awhile. To repro faster:

  $ grep qtest-i386/qos-test Makefile.mtest
  .test.name.229 := qtest-i386/qos-test
  $ make run-test-229
  Running test qtest-i386/qos-test
  ** Message: 18:40:49.821: Test g_error hang ...

  ** (tests/qtest/qos-test:3820728): ERROR **: 18:40:49.821: Pretend something timed out
  ERROR qtest-i386/qos-test - Bail out! FATAL-ERROR: Pretend something timed out

  At this point things are hung because tap-driver.pl is still waiting
  for input because qemu is still running.

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