Fixes an issue reported on libevent-users in the thread "a dead
looping bug when changing system time backward". Previously, if time
jumped forward 1 hour[*] and we had a one-second periodic timer event,
that event would get invoked 3600 times. That's almost certainly not
what anybody wants.
In a future version of Libevent, we should expose the amount of time
that the callbac kwould have been invoked somehow.
[*] Forward time jumps can happen with nonmonotonic clocks, or with
clocks that jump on suspend/resume. It can also happen from
Libevent's point of view if the user exits from event_base_loop() and
doesn't call it again for a while.
Apparently, kevent fails gracefully if there is not enough space in its
output events array to report every _event_... but it just dies and returns
-1 if there is not enough space to report every _error_.
There are a couple of possible fixes here. One would to handle -1
returns from kevent better by re-growing the array and retrying... but
that seems a little error prone. Instead, I'm just going to say that
the events array must be large enough to handle all the errors.
This patch also adds a unit test designed to make sure that our
many-events-out code works even if not all the events are added at
once.
The only changes needed were to handle the fact that the methodname
"epoll (with changelist)" matches the environment variable
EVENT_NOEPOLL rather than the imaginary "EVENT_EPOLL (WITH CHANGELIST)".
Current versions of the Linux kernel don't seem to remove the struct
epitem for a given (file,fd) combo when the fd is closed unless the
file itself is also completely closed. This means that if you do:
fd = dup(fd_orig);
add(fd);
close(fd);
dup2(fd_orig, fd);
add(fd);
you will get an EEXIST when you should have gotten a success. This
could cause warnings and dropped events when using dup and epoll.
The solution is pretty simple: when we get an EEXIST from
EPOLL_CTL_ADD, we retry with EPOLL_CTL_MOD.
Unit test included to demonstrate the bug.
Found due to the patient efforts of Gilad Benjamini; diagnosed with
help from Nicholas Marriott.
When using the signal.c signal backend, Libevent currently only allows
one event_base to actually receive signals at a time. (This has been
the behavior since at least 1.4 and probably much earlier.) Now, we
detect and warn if you're likely to be racing about which signal goes
to which thread.
We also add a lock to control modifications of the evsig_base field,
to avoid race conditions like those found by Jason Toffaletti.
Also, more comments. Comments are good.
To be fair, when char can be signed, if toupper doesn't take negative
characters, toupper(char) is a very bad idea. So let's just use the
nice safe EVUTIL_TOUPPER instead. (It explicitly only upcases ASCII,
but we only use it for identifiers that we know to be ASCII anyway).
On all the backends on this little mac laptop, that behavior is to
report a remote socket close as both EV_READ and EV_WRITE.
Historically, we had problem for some of these behaviors on some
backends, so let's make sure that such behaviors don't come back.
The "current_base" symbol was never actually declared in an exported
header; it's hideously deprecated, and it was the one remaining
exported symbol (fwict) that was prefixed with neither ev nor
bufferevent nor _ev nor _bufferevent.
codesearch.google.com turns up no actual attempts to use our
current_base from outside libevent.
The EVUTIL_CLOSESOCKET() macro required you to include unistd.h in your
source for POSIX. We might as well turn it into a function: an extra
function call is going to be cheap in comparison with the system call.
We retain the EVUTIL_CLOSESOCKET() macro as an alias for the new
evutil_closesocket() function.
(commit message from email by Nick and Sebastian)
Calling event_base_loop on a base from inside a callback invoked by
that same base, or from two threads at once, has long been a way to
get exceedingly hard-to-diagnose errors. This patch adds code to
detect such reentrant invocatinos, and exit quickly with a warning
that should explain what went wrong.
This is mainly intended to ensure that we don't get hung up on
the 64-handle limit that lots of O(n) Windows functions (but FWICT
not select) like to enforce.
Remeber, win32 has a socket type that's actually a handle, so if
there's a chance that code is run on win32, we can't use "int" as the
socket type.
This isn't a blind search-and-replace: sometimes an fd is really in
fact for a file, and not a socket at all.
Previously, we assumed that we would have setenv/unsetenv everywhere
but WIN32, where we could fake them with putenv. This isn't so: some
other non-windows systems lack setenv/unsetenv, and some of them lack
putenv too.
The first part of the solution, then, is to detect setenv/unsetenv/
putenv from configure.in, and to fake setenv/unsetenv with putenv
whenever we have the latter but not one of the former.
But what should we do when we don't even have putenv? We could do
elaborate tricks to manipulate the environ pointer, but since we're
only doing this for the unit tests, let's just skip the one test in
question that uses setenv/unsetenv.
Libevent's current timeout code is relatively optimized for the
randomly scattered timeout case, where events are added with their
timeouts in no particular order. We add and remove timeouts with
O(lg n) behavior.
Frequently, however, an application will want to have many timeouts
of the same value. For example, we might have 1000 bufferevents,
each with a 2 second timeout on reading or writing. If we knew this
were always the case, we could just put timeouts in a queue and get
O(1) add and remove behavior. Of course, a queue would give O(n)
performance for a scattered timeout pattern, so we don't want to
just switch the implementation.
This patch gives the user the ability to explicitly tag certain
timeout values as being "very common". These timeout values have a
cookie encoded in the high bits of their tv_usec field to indicate
which queue they belong on. The queues themselves are each
triggered by an entry in the minheap.
See the regress_main.c code for an example use.
svn:r1517
