In real world usage, there have been reported signaler failures where the
eventfd read() or socket recv() system call in signaler::recv() fails,
despite having made a prior successful signaler::wait() call.
this patch creates a signaler::recv_failable() method that allows
unreadable eventfd / socket to return an error without asserting.
Of course people still "can" distributed the sources under the
LGPLv3. However we provide COPYING.LESSER with additional grants.
Solution: specify these grants in the header of each source file.
Copyrights had become ads for Sustrik's corporate sponsors, going against the original
agreement to share copyrights with the community (that agreement was: one line stating
iMatix copyright + one reference to AUTHORS file). The proliferation of corporate ads
is also unfair to the many individual authors. I've removed ALL corporate title from
the source files so the copyright statements can now be centralized in AUTHORS and
source files can be properly updated on an annual basis.
Storing commands in OS socket buffers caused whole lot of
problems when free space in the buffer ran out. This patch
stores commands in ypipes instead and uses socketpair just
to signal the other thread, ie. at most one byte is stored
in the socketpair at any single instant.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
For historical reasons queue to transfer commands between
threads was called 'signaler'. Given that it was used to
pass commands rather than signals it was renamed to 'mailbox',
see Erlang mailboxes.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
If the socketpair used by signaler_t fills up, this can lead to deadlock.
This patch provides partial resolution by attempting to resize SO_SNDBUF on
the writer side, and if that fails we shall at least assert rather than
hang.
I've also refactored the signaler_t code to make the platform-dependent
parts clearer and have tested both the MSG_DONTWAIT and standard POSIX path
in recv.
The Win32 implementation currently does not implement resizing as I'm not
convinced that it's safe, but it will also assert like other platforms if
signaler_t::send() cannot succeed.
The OpenVMS implementation has been carried forward but is untested.
Signed-off-by: Martin Lucina <mato@kotelna.sk>
