On Thu, 2014-03-27 at 14:12 +0100, Andreas Färber wrote:
> Am 27.03.2014 14:09, schrieb Markus Armbruster:
> > Reply after commit, sorry.
> >
> > Stefan Hajnoczi <stefa...@redhat.com> writes:
> >
> >> If an assertion fails during qtest_init() the SIGABRT handler is
> >> invoked. This is the correct behavior since we need to kill the QEMU
> >> process to avoid leaking it when the test dies.
> >>
> >> The global_qtest pointer used by the SIGABRT handler is currently only
> >> assigned after qtest_init() returns. This results in a segfault if an
> >> assertion failure occurs during qtest_init().
> >>
> >> Move global_qtest assignment inside qtest_init(). Not pretty but let's
> >> face it - the signal handler dependeds on global state.
> >>
> >> Reported-by: Marcel Apfelbaum <marce...@redhat.com>
> >> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> >> ---
> >> tests/libqtest.c | 3 ++-
> >> tests/libqtest.h | 4 +---
> >> 2 files changed, 3 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/tests/libqtest.c b/tests/libqtest.c
> >> index c9e78aa..f387662 100644
> >> --- a/tests/libqtest.c
> >> +++ b/tests/libqtest.c
> >> @@ -120,7 +120,7 @@ QTestState *qtest_init(const char *extra_args)
> >> qemu_binary = getenv("QTEST_QEMU_BINARY");
> >> g_assert(qemu_binary != NULL);
> >>
> >> - s = g_malloc(sizeof(*s));
> >> + global_qtest = s = g_malloc(sizeof(*s));
> >>
> >> socket_path = g_strdup_printf("/tmp/qtest-%d.sock", getpid());
> >> qmp_socket_path = g_strdup_printf("/tmp/qtest-%d.qmp", getpid());
> >> @@ -181,6 +181,7 @@ QTestState *qtest_init(const char *extra_args)
> >> void qtest_quit(QTestState *s)
> >> {
> >> sigaction(SIGABRT, &s->sigact_old, NULL);
> >> + global_qtest = NULL;
> >>
> >> kill_qemu(s);
> >> close(s->fd);
> >> diff --git a/tests/libqtest.h b/tests/libqtest.h
> >> index 9deebdc..7e23a4e 100644
> >> --- a/tests/libqtest.h
> >> +++ b/tests/libqtest.h
> >> @@ -335,8 +335,7 @@ void qtest_add_func(const char *str, void (*fn));
> >> */
> >> static inline QTestState *qtest_start(const char *args)
> >> {
> >> - global_qtest = qtest_init(args);
> >> - return global_qtest;
> >> + return qtest_init(args);
> >> }
> >>
> >> /**
> >> @@ -347,7 +346,6 @@ static inline QTestState *qtest_start(const char *args)
> >> static inline void qtest_end(void)
> >> {
> >> qtest_quit(global_qtest);
> >> - global_qtest = NULL;
> >> }
> >>
> >> /**
> >
> > Before this patch, the libqtest API could theoretically support multiple
> > simultaneous instances of QTestState. This patch kills that option,
> > doesn't it?
>
> Ouch, I thought I had looked out for that...
>
> >
> > If yes: fine with me, we don't need it anyway.
>
> We do. Migration and ivshmem are examples that need two machines - might
> explain why my ivshmem-test was behaving unexpectedly.
>
> Apart from reverting, what are our options?
The problem is in 'kill_qemu' function, which is called from
SIGABRT signal handler. The later needs to know the QTestState
in order to kill the QEMU process.
Without this patch, kill_qemu will cause a segfault because of:
static void kill_qemu(QTestState *s)
{
if (s->qemu_pid != -1) {
...
s can be NULL if there is an assert in qtest_init.
I suppose we can find a different approach, like keeping
the qemu_pid(s) in another statically defined struct.
Thanks,
Marcel
>
> Regards,
> Andreas
>
> > But shouldn't we clean
> > up the API then? It typically provides a function taking a QTestState
> > parameter, and a wrapper that passes global_qtest. If global_qtest is
> > the only QTestState we can have, having the former function is
> > pointless.
> >
>
>
