It seems that allowing the GCancellable to be finalised in either the
main thread or the worker thread sometimes leads to crashes when running
on CI.
I cannot reproduce these crashes locally, and various analyses with
memcheck, drd and helgrind have failed to give any clues.
Fix this for this particular test case by deferring destruction of the
`GCancellable` instances until after the worker thread has joined.
That’s OK because this test is specifically checking a race between
`g_cancellable_cancel()` and disposal of a `GCancellableSource`.
The underlying bug remains unfixed, though, and I can only hope that we
eventually find a reliable way of reproducing it so it can be analysed
and fixed.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
The test added for #1841 spawned 100000 threads. That was fine on a
desktop machine, but on a heavily loaded CI machine, it could result in
large (and unpredictable) slowdowns, resulting in the test taking over
120s in about 1 in 5 runs, and hence failing that CI pipeline due to a
timeout. When passing normally on CI, the test would take around 90s.
Here’s a histogram of time per iteration on a failing (timed out) test
run. Each iteration is one thread spawn:
Iteration duration (µs) | Frequency
------------------------+----------
≤100 | 0
100–200 | 30257
200–400 | 13696
400–800 | 1046
800–1000 | 123
1000–2000 | 583
2000–4000 | 3779
4000–8000 | 4972
8000–10000 | 1027
10000–20000 | 2610
20000–40000 | 650
40000–80000 | 86
80000–100000 | 10
100000–200000 | 2
>200000 | 0
There’s no actual need for the test to spawn 100000 threads, so rewrite
it to reuse a single thread, and pass new data to that thread.
Reverting the original commit (e4a690f5dd) reproduces the failure on
100 out of 100 test runs with this commit applied, so the test still
works.
The test now takes 3s, rather than 11s, to run on my computer, and has
passed when run with `meson test --repeat 1000 cancellable`.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
There’s a minor race condition between cancellation of a `GCancellable`,
and disposal/finalisation of a `GCancellableSource` in another thread.
Thread A Thread B
g_cancellable_cancel(C)
→cancellable_source_cancelled(C, S)
g_source_unref(S)
cancellable_source_dispose(S)
→→g_source_ref(S)
→→# S is invalid at this point; crash
Thankfully, the `GCancellable` sets `cancelled_running` while it’s
emitting the `cancelled` signal, so if `cancellable_source_dispose()` is
called while that’s high, we know that the thread which is doing the
cancellation has already started (or is committed to starting) calling
`cancellable_source_cancelled()`.
Fix the race by resurrecting the `GCancellableSource` in
`cancellable_source_dispose()`, and signalling this using
`GCancellableSource.resurrected_during_cancellation`. Check for that
flag in `cancellable_source_cancelled()` and ignore cancellation if it’s
set.
The modifications to `resurrected_during_cancellation` and the
cancellable source’s refcount have to be done with `cancellable_mutex`
held so that they are seen atomically by each thread. This should not
affect performance too much, as it only happens during cancellation or
disposal of a `GCancellableSource`.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Fixes: #1841
`g_assert()` is compiled out if `G_DISABLE_ASSERT` is defined, and
`g_assert_*()` gives more detailed failure messages.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Those tests seem to regularly fail because a timeout (which we're
measuring outside the function that times out) is too long, which can
happen when the system is busy.
Don't run those tests unless "thorough" tests are requested. This
disables those tests by default.
Bail out! GLib-GIO:ERROR:../gio/tests/socket.c:1167:test_timed_wait: assertion failed (poll_duration < 112000): (114254 < 112000)
Bail out! GLib-GIO:ERROR:../gio/tests/cancellable.c:167:on_mock_operation_ready: assertion failed (error == (g-io-error-quark, 19)): error is NULL
Commit f975858e86 removed the NULL check in g_cancellable_cancel() by
accident which makes it crash when called with NULL.
Add the check back and add a test so this doesn't happen again.
Fixes#1710
Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
The test was assuming that all cancelled ops would finish within a
certain amount of time, but this often failed under valgrind. Instead,
just run the loop until all of the ops have actually finished.
https://bugzilla.gnome.org/show_bug.cgi?id=682560
* Update documentation to note that GCancellable can be used
concurrently by multiple operations.
* Add documentation to g_cancellable_reset that behavior is
undefined if called from within cancelled handler.
* Add test for multiple concurrent operations using the same
cancellable.
https://bugzilla.gnome.org/show_bug.cgi?id=656387
