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spa: support: loop: handle cancellation better

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Register a pthread cleanup handler to guarantee
that `spa_source::{priv, rmask}` are cleared even
if the thread is cancelled while the loop is dispatching.

This is necessary, otherwise `spa_source::priv` could point
to the stack of the cancelled thread, which will lead to
problems like this later:

  Program terminated with signal SIGSEGV, Segmentation fault.
  #0  0x00007f846b025be2 in detach_source (source=0x7f845f435f60) at ../spa/plugins/support/loop.c:144
  144      e->data = NULL;
  [Current thread is 1 (LWP 5274)]
  (gdb) p e
  $1 = (struct spa_poll_event *) 0x7f845e297820
  (gdb) bt
  #0  0x00007f846b025be2 in detach_source (source=0x7f845f435f60) at ../spa/plugins/support/loop.c:144
  #1  0x00007f846b0276ad in free_source (s=0x7f845f435f60) at ../spa/plugins/support/loop.c:359
  #2  0x00007f846b02a453 in loop_destroy_source (object=0x7f845f3af478, source=0x7f845f435f60) at ../spa/plugins/support/loop.c:786
  #3  0x00007f846b02a886 in impl_clear (handle=0x7f845f3af478) at ../spa/plugins/support/loop.c:859
  #4  0x00007f846b172f40 in unref_handle (handle=0x7f845f3af450) at ../src/pipewire/pipewire.c:211
  #5  0x00007f846b173579 in pw_unload_spa_handle (handle=0x7f845f3af478) at ../src/pipewire/pipewire.c:346
  #6  0x00007f846b15a761 in pw_loop_destroy (loop=0x7f845f434e30) at ../src/pipewire/loop.c:159
  #7  0x00007f846b135d8e in pw_data_loop_destroy (loop=0x7f845f434cb0) at ../src/pipewire/data-loop.c:166
  #8  0x00007f846b12c31c in pw_context_destroy (context=0x7f845f41c690) at ../src/pipewire/context.c:485
  #9  0x00007f846b3ddf9e in jack_client_close (client=0x7f845f3c1030) at ../pipewire-jack/src/pipewire-jack.c:3481
  ...
This commit is contained in:
Barnabás Pőcze 2022-06-01 16:36:56 +02:00
parent 0d51f3b74e
commit 479896279e
2 changed files with 99 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

29
spa/plugins/support/loop.c
View file

@ -370,6 +370,24 @@ static inline void process_destroy(struct impl *impl)
spa_list_init(&impl->destroy_list);
}
struct cancellation_handler_data {
struct spa_poll_event *ep;
int ep_count;
};
static void cancellation_handler(void *closure)
{
const struct cancellation_handler_data *data = closure;
for (int i = 0; i < data->ep_count; i++) {
struct spa_source *s = data->ep[i].data;
if (SPA_LIKELY(s)) {
s->rmask = 0;
s->priv = NULL;
}
}
}
static int loop_iterate(void *object, int timeout)
{
struct impl *impl = object;
@ -384,6 +402,9 @@ static int loop_iterate(void *object, int timeout)
spa_loop_control_hook_after(&impl->hooks_list);
impl->polling = false;
struct cancellation_handler_data cdata = { ep, nfds };
pthread_cleanup_push(cancellation_handler, &cdata);
/* first we set all the rmasks, then call the callbacks. The reason is that
* some callback might also want to look at other sources it manages and
* can then reset the rmask to suppress the callback */
@ -409,13 +430,7 @@ static int loop_iterate(void *object, int timeout)
s->func(s);
}
for (i = 0; i < nfds; i++) {
struct spa_source *s = ep[i].data;
if (SPA_LIKELY(s)) {
s->rmask = 0;
s->priv = NULL;
}
}
pthread_cleanup_pop(true);
return nfds;
}

77
test/test-loop.c
View file

@ -374,6 +374,82 @@ PWTEST(destroy_managed_source_before_dispatch_recurse)
return PWTEST_PASS;
}
struct ctwd_data {
struct spa_source source;
int handler_running_barrier;
};
static void ctwd_event_handler(struct spa_source *source)
{
struct ctwd_data *data = source->data;
write_eventfd(data->handler_running_barrier);
for (;;)
pause(); /* the purpose of this is to block the loop */
}
static int ctwd_add_source(struct spa_loop *loop, bool async, uint32_t seq,
const void *d, size_t size, void *user_data)
{
struct ctwd_data *data = user_data;
pwtest_neg_errno_ok(spa_loop_add_source(loop, &data->source));
return 0;
}
PWTEST(cancel_thread_while_dispatching)
{
static const struct spa_dict_item data_loop_props_items[] = {
{ "loop.cancel", "true" },
};
static const struct spa_dict data_loop_props = SPA_DICT_INIT_ARRAY(data_loop_props_items);
struct ctwd_data data = {
.source = {
.data = &data,
.func = ctwd_event_handler,
.mask = SPA_IO_IN,
.fd = eventfd(0, 0),
},
.handler_running_barrier = eventfd(0, 0),
};
pw_init(NULL, NULL);
struct pw_data_loop *dl = pw_data_loop_new(&data_loop_props);
pwtest_ptr_notnull(dl);
struct pw_loop *l = pw_data_loop_get_loop(dl);
pwtest_ptr_notnull(l);
pwtest_neg_errno_ok(pw_data_loop_start(dl));
pw_loop_invoke(l, ctwd_add_source, 0, NULL, 0, true, &data);
pwtest_ptr_notnull(data.source.loop);
write_eventfd(data.source.fd);
read_eventfd(data.handler_running_barrier);
pwtest_neg_errno_ok(pw_data_loop_stop(dl));
/* these are the important checks */
pwtest_ptr_null(data.source.priv);
pwtest_int_eq(data.source.rmask, UINT32_C(0));
pw_loop_remove_source(l, &data.source);
pw_data_loop_destroy(dl);
close(data.source.fd);
close(data.handler_running_barrier);
pw_deinit();
return PWTEST_PASS;
}
PWTEST_SUITE(support)
{
pwtest_add(pwtest_loop_destroy2, PWTEST_NOARG);
@ -381,6 +457,7 @@ PWTEST_SUITE(support)
pwtest_add(pwtest_loop_recurse2, PWTEST_NOARG);
pwtest_add(destroy_managed_source_before_dispatch, PWTEST_NOARG);
pwtest_add(destroy_managed_source_before_dispatch_recurse, PWTEST_NOARG);
pwtest_add(cancel_thread_while_dispatching, PWTEST_NOARG);
return PWTEST_PASS;
}