metar fetcher. Effectively this caused the metar thread and the main
thread to both attempt to fetch weather data. This could lead to long pauses
when the main thread decided to fetch the weather, and introduced a race
condition that could cause a segfault/crash.
Investigating this issue, I discovered that even longer ago, someone confused
#defines and #ifdef symbols with C/C++ variables. If I #define XYZ 0 it is
defined so #ifdef XYZ is true, not false like a variable. Our thread
detection made this mistake and there were follow up patches to work around
it.
So I fixed the configure script (ahhh, reading the autoconf manual is highly
recommended excercise for people editing the configure.ac file.) I also
discovered that we were hardwiring with_threads=yes with no way via configure
options to disable threads from the build so I fixed that.
Then I patched up the #ifdef's scattered through the code to match the
configure script changes, oh and by the way, I stumbled upon a past typo
that led to the race condition in the metar fetching thread and fixed that.
Wouldn't it be better to prepare the whole list of paths (or two
separate ones for Terrain/Objects if necessary) in FGGlobals::set_fg_scenery,
and to pass the vector<string>s to FGTileEntry::load? It doesn't seem to make
a lot of sense to split the path up, modify it, mount it together to one string
again, and then let FGTileEntry::load split it up again.
Here we go:
Main/globals.cxx
================
As fg_scenery is now a string_list, we don't need initialization. Furthermore,
this list is cleared with every set_fg_scenery() call.
ctor: create default dir from fg_root if necessary. Otherwise check all paths
of --fg-scenery/FG_SCENERY: If the path doesn't exist, ignore it. If it contains
a dir Terrain and/or Objects, then only add that to the list. If it contains
neither, then use the path as is.
Scenery/tileentry.cxx
=====================
Trivial: don't split a "base path", but use the given path_list as is.
(I considered a variable name "path_list" better suited than "search".)
Scenery/FGTileLoader.cxx
========================
No more fiddling with sub-paths. This has to be delivered by get_fg_scenery
already.
configure and compile out-of-the-box on a MinGW target:
Use -lSDL instead of -lglut32 on windows builds when --enable-sdl
is set.
Link against alut.dll in addition to openal32.dll.
Replace BSD bcopy() with ANSI C memmove() in a few places. This is
simpler than trying to abstract it out as a platform dependency in a
header file; bcopy() has never been standard.
The ENABLE_THREADS handling has changed to be set to 0 when threads
are not in use. This breaks expressions like #ifdef ENABLE_THREADS.
Replace with a slightly more complicated expression. It might have
been better to fix the configure.ac script, but I didn't know how and
this whole setting is likely to go away soon anyway.
The MinGW C runtime actually does include snprintf, so only MSVC
builds (and not all WIN32 ones) need _snprintf in JSBSim/FGState.cpp
Building on a platform with no glut at all exposed some spots where
plib/pu.h was being included without a toolkit setting (it defaults to
glut). Include fg_os.hxx first.
And when still using glut, glut.h has a bizarre dependency on a
_WCHAR_T_DEFINED symbol. It it's not defined, it tries to redefine
(!!) wchar_t to disasterous effect.
search when loading scenery tiles. (I am not set on using ";" as the
delimiter because it is a command separator in unix, but ":" is a critical
part of the windows file naming scheme (c:\foo\bar) so that is even worse.)
Example:
--fg-scenery=/stage/fgfs04/curt/Scenery-0.9.1/Scenery;/stage/helio1/curt/Scenery
-0.7.9
a crash when relocating to a new airport. Pending work from the old
area is now just completed as normal, rather than trying to empty the various
queues in their various stages when can lead to many problems in a threaded
environment.
to have attached an ssg loaded object to this branch, then plib will remove
it and all it's states (and textures) which will call opengl api commands
which will crash the program if run from a separate thread from the main render
thread.
- model loading deferred to primary thread
- tile removal deferred to paging thread
- other tweaks and rearrangments.
Airport signs
- first stab at some support for adding taxiway and runway signs. This
is non-optimal, but I'm under the gun for a demo.
a newly loaded tile to the scene graph. Instead it puts it in a queue
for the tile manager. I've used your counter_hack to check the loaded
queue and add any tiles to the scene graph. I was playing around with
the counter_hack so there might be some commented out code, etc. I also
changed some SG_DEBUGs to SG_INFOs so I could track the tile loading.
He writes:
Here are the final changes to add threads to the tile loading. All the
thread related code is in the new FGTileLoader class.
./configure.in
./acconfig.h
Added --with-threads option and corresponding ENABLE_THREADS
definition. The default is no threads.
./src/Scenery/tilemgr
Removed load_queue and associated references. This has been replaced by
a new class FGTileLoader in FGNewCache.
Made the global variable global_tile_cache a member.
schedule_needed(): removed global_tile_cache.exists() tests since
sched_tile() effectively repeats the test.
initialize_queue(): removed code that loads tiles since this is now
performed by FGTileLoader.
update(): ditto
./src/Scenery/newcache
Added new class FGTileLoader to manage tile queuing and loading.
tile_map typedefs are private.
exists() is a const member function.
fill_in(): deleted
load_tile(): added.
./src/Scenery/FGTileLoader
The new threaded tile loader. Maintains a queue of tiles waiting to be
loaded and an array of one or more threads to load the tiles. Currently
only a single thread is created. The queue is guarded by a mutex to
synchronize access. A condition variable signals the thread when the
queue is non-empty.
CLO: I made a few tweaks to address a couple issues, hopefully what we
have is solid, but now we kick it out to the general public to see. :-)
