Linux provides some features that allow avoiding extra calls to
fcntl when creating new nonblocking/close-on-exec sockets, so
we can add wrapper functions to emulate those when they are not
available.
Additionally, even when we are emulating those functions, we can
take a fast path that cuts our fcntl calls in half: we don't need to
look up the previous value of a file's flags when we have just
created it.
We were doing this because of (correct) reports that NetBSD gives an
EBADF when you try to add the write side of a pipe for which the
read side has been closed. But on most kqueue platforms, that
doesn't happen, and on *all* kqueue platforms, reporting a
nonexistent fd (which we usually have if we have seen EBADF) as
readable tends to give programs a case of the vapors.
Nicholas Marriott wrote the original patch here; I did the comment
fixes.
This is not a perfect fix, but it's much much better than the
current buggy behavior, which could lead to filtering SSL
connections that just stopped reading.
Based on ideas by Maseeb Abdul Qadir and Mark Ellzey.
Those pointers were once used to maintain a complete list of
inserted IO and signal events. But such a list is now available by
walking over ev_io_map and ev_signal_map! So all they did was
require extra pointer operations to maintain, and extra 8-16 bytes
of storage in each struct event.
To be cowardly and keep the option of going back to having this
redundancy, I'm wrapping the removed code in a set of ifdefs.
This is a first cut; it needs cleanups and stress-testing!! In
particular, it just plain disables a couple of functions that could
probably be saved.
There seems to be a need for an evmap_{io,signal}_foreach() or something.
We used to use the needs_reinit flag in struct eventop to indicate
whether an event backend had shared state across a fork(), and
therefore would require us to construct a new event backend. But
when we realized that the signal notification fds and the thread
notification fds would always be shared across forks, we stopped
looking at it.
This patch restores the old behavior so that poll, select, and
win32select don't need to do a linear scan over all pending
fds/signals when they do a reinit. Their life is hard enough
already.
Previously, event_reinit required a bunch of really dubious hacks,
and violated a lot of abstraction barriers to mess around with lists
of internal events and "pretend" to re-add them.
The new (and fairly well commented!) implementation tries to be much
smarter, by isolating the changes as much as possible to the backend
state, and minimizing the amount of abstraction violations.
Specifically, we now use event_del() to remove events we want to
remove, rather than futzing around with queues in event_reinit().
To avoid bogus calls to evsel->del(), we temporarily replace evsel
with a null-object stub.
Also, we now push the responsibility for calling evsel->add() down
into the evmap code, so that we don't actually need to unlink and
re-link all of our events.
Some of our unit tests and sample code need functions and structures
defined in an -internal.h header. But that can freak out OpenSolaris,
where stdio.h wants to define _FILE_OFFSET_BITS unless it's already
defined, and then evconfig-internal.h defines it. Regular users
should never ever use our -internal.h headers, so the solution is
to make sure that if we're going to use them ourselves, we do so
before system headers.
