And also mention what the expected values of errno are going to be.
write_control() will only ever return FALSE if there was a critical error. It
will never return because of EINTR, EAGAIN or EWOULDBLOCK.
read_control() will return FALSE if there was no byte to read, in which case
errno would be EWOULDBLOCK.
In all other cases there was a critical error.
https://bugzilla.gnome.org/show_bug.cgi?id=750397
On timer GstPolls it will cause the control socket state to become
inconsistent as now one less read_control() than write_control() be would
needed.
Similarly, read_control() and write_control() are only valid on timer
GstPolls.
https://bugzilla.gnome.org/show_bug.cgi?id=750397
This addresses slightly different race conditions on Linux and Windows, and
fixes gst_poll_read_control() when control_pending == 0.
On Linux, the socketpair() used for control should not be made O_NONBLOCK.
If there's any propagation delay between set->control_write_fd.fd and
set->control_read_fd.fd, even the mutex now held will not be sufficient to
prevent a race condition. There's no benefit to using O_NONBLOCK, here.
Only liabilities.
For Windows, it's necessary to fix the race condition between testing
set->control_pending and performing WAKE_EVENT()/RELEASE_EVENT(). This is
accomplished by acquiring and holding set->lock, for both of these operations.
We could optimize the Linux version by making this Windows-specific.
For consistency with the Linux implementation, Windows' RELEASE_EVENT()
has also been made to block, although it should never happen.
Also, changed release_wakeup() to return TRUE and decrement control_pending
only when > 0. Furthermore, RELEASE_EVENT() is called only when
control_pending == 1.
Finally, changed control_pending to use normal, non-atomic arithmetic
operations, since it's now protected by set->lock.
Note: even though the underlying signaling mechanisms are blocking,
release_wakeup() is effectively non-blocking, as it will only attempt to read
from control_read_fd.fd after a byte has been written to control_write_fd.fd
or WaitForSingleObject() after it's been signaled.
https://bugzilla.gnome.org/show_bug.cgi?id=750397
SetEvent() seems to not call SetLastError(0) internally, so checking last
error after calling SetEvent() may return the error from an earlier W32 API
call. Fix this by calling SetlastError(0) explicitly.
Currently WAKE_EVENT() code is cramped into a macro and doesn't look to be
entirely correct. Particularly, it does not check the return value of
SetEvent(), only the thread-local W32 error value. It is likely that SetEvent()
actually just returns non-zero value, but the code mistakenly thinks that the
call has failed, because GetLastError() seems to indicate so.
https://bugzilla.gnome.org/show_bug.cgi?id=733805
Support for (nullable) was added to G-I at the same time as nullable
return values. Previous versions of G-I will not mark return values as
nullable, even when an (allow-none) annotation is present, so it is
not necessary to add (allow-none) annotations for compatibility with
older versions of G-I.
https://bugzilla.gnome.org/show_bug.cgi?id=730957
passing argument 1 of 'g_mutex_lock' discards 'const' qualifier from pointer target type
passing argument 1 of 'g_mutex_unlock' discards 'const' qualifier from pointer target type
See #651514 for details. It's apparently impossible to write code
that avoids both type punning warnings with old g_atomic headers and
assertions in the new. Thus, macros and a version check.
if set->control_pending is set to 0 but we didn't not succed reading
the control socket, future calls to gst_poll_wait() will be awaiken
by the control socket which will not be released properly because
set->control_pending is already 0, causing an infinite loop.
Failing to do so in the Windows case (implicitly triggered otherwise)
would have a subsequent _wait return immediately leading to high CPU
usage timeout loops.
Fixes#640675.
We need to reset the revents field of each pollfd when reading the results
from select else we'll end up with stray info from previous calls to
select.
This may cause crashes when logging is enabled, especially on windows.
It's not safe to pass random pointers to g_type_check_instance_is_a().
Fixes#611719.
Add a special timer mode in GstPoll that makes it only use the control socket
with a timeout to schedule timeouts. Also add a pair of methods to wakeup the
timeout thread.
API: GstPoll::gst_poll_new_timer()
API: GstPoll::gst_poll_write_control()
API: GstPoll::gst_poll_read_control()
Add a new variable that keeps track of the status of the control socket. This
allows us to avoid doing a read() on the control socket when we did not write
anything to it.
Fixes#568438.
