On Tue, 5 Aug 2014 11:39:49 +0200 Marek Chalupa <mchqwe...@gmail.com> wrote:
> wl_display_read_events() can make a thread wait until some other thread > ends reading. Normally it wakes up all threads after the reading is > done. But there's a place when it does not get to waking up the threads > - when an error occurs. This test reveals bug that can block programs. > > If a thread is waiting in wl_display_read_events() and another thread > calls wl_display_read_events and the reading fails, > then the sleeping thread is not woken up. This is because > display_handle_error is using old pthread_cond instead of new > display->reader_cond, that was added along with wl_display_read_events(). > --- > tests/display-test.c | 90 > ++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 90 insertions(+) > > diff --git a/tests/display-test.c b/tests/display-test.c > index e212942..26f946b 100644 > --- a/tests/display-test.c > +++ b/tests/display-test.c > @@ -31,6 +31,7 @@ > #include <errno.h> > #include <sys/types.h> > #include <sys/stat.h> > +#include <pthread.h> > > #include "wayland-private.h" > #include "wayland-server.h" > @@ -323,3 +324,92 @@ TEST(post_nomem_tst) > > display_destroy(d); > } > + > +static void > +register_reading(struct wl_display *display) > +{ > + while(wl_display_prepare_read(display) != 0 && errno == EAGAIN) > + assert(wl_display_dispatch_pending(display) >= 0); > + assert(wl_display_flush(display) >= 0); > +} > + > +static void * > +thread_read_error(void *data) > +{ > + struct client *c = data; > + > + register_reading(c->wl_display); > + > + /* > + * Calling the read right now will block this thread > + * until the other thread will read the data. > + * However, after invoking an error, this > + * thread should be woken up or it will block indefinitely. > + */ > + c->display_stopped = 1; > + assert(wl_display_read_events(c->wl_display) == 0); > + > + wl_display_dispatch_pending(c->wl_display); > + assert(wl_display_get_error(c->wl_display)); > + > + pthread_exit(NULL); > +} > + > +/* test posting an error in multi-threaded environment. */ > +static void > +threading_post_err(void) > +{ > + struct client *c = client_connect(); > + pthread_t thread; > + > + /* register read intention */ > + register_reading(c->wl_display); > + > + /* use this var as an indicator that thread is sleeping */ > + c->display_stopped = 0; > + > + /* create new thread that will register its intention too */ > + assert(pthread_create(&thread, NULL, thread_read_error, c) == 0); > + > + /* make sure thread is sleeping. It's a little bit racy > + * (setting display_stopped to 1 and calling wl_display_read_events) > + * so call usleep once again after the loop ends - it should > + * be sufficient... */ > + while (c->display_stopped == 0) > + usleep(500); > + > + usleep(10000); > + > + /* so now we have sleeping thread waiting for a pthread_cond signal. > + * The main thread must call wl_display_read_events(). > + * If this call fails, then it won't call broadcast at the > + * end of the function and the sleeping thread will block indefinitely. > + * Make the call fail and watch if libwayland will unblock the thread! > */ > + > + /* create error on fd, so that wl_display_read_events will fail. > + * The same can happen when server hangs up */ > + close(wl_display_get_fd(c->wl_display)); > + /* this read events will fail and will > + * post an error that should wake the sleeping thread > + * and dispatch the incoming events */ > + assert(wl_display_read_events(c->wl_display) == -1); > + > + /* kill test in 3 seconds. This should be enough time for the > + * thread to exit if it's not blocking. If everything is OK, than > + * the thread was woken up and the test will end before the SIGALRM */ > + alarm(3); > + pthread_join(thread, NULL); > + > + wl_proxy_destroy((struct wl_proxy *) c->tc); > + wl_display_disconnect(c->wl_display); > +} > + > +TEST(threading_errors_tst) > +{ > + struct display *d = display_create(); > + > + client_create(d, threading_post_err); > + display_run(d); > + > + display_destroy(d); > +} This looks good. I'll be merging this and likely the others after I get the refreshed series adding the test-compositor framework, as discussed in irc. Thanks, pq _______________________________________________ wayland-devel mailing list wayland-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/wayland-devel