1. Comment that SDL_SetThreadPriority will make any necessary system changes when applying priority.
2. Add a hint to override SDL's default behavior for scheduler policy.
3. Modify the pthreads SDL_SetThreadPriority so that instead of just using the current thread scheduler policy it will change it to a policy that should work best for the requested priority.
4. Add hint checks in SDL_SetThreadPriority so that #3 can be overridden if desired.
5. Modify the Linux SDL_SetThreadPriority so that in the case that policy, either by SDL defaults or from the hint, is a realtime policy it uses the realtime rtkit API.
6. Prior to calling rtkit on Linux make the necessary thread state changes that rtkit requires. Currently this is done every time as it isn't expected that SDL_SetThreadPriority will be called repeatedly for a thread.
This avoids the need to malloc something extra, use a semaphore, etc, and
fixes Emscripten with pthreads support, which might not spin up a web worker
until after SDL_CreateThread returns and thus can't wait on a semaphore at
this point in any case.
Fixes Bugzilla #5064.
Ethan Lee
Attached is a diff that I used to get SetThreadPriority working locally. I still have no idea what the minimum SDK version is since Microsoft never documented it, but it's worth pointing out that they're much more aggressive about using the latest VS and UWP SDK anyway (for example, an updated Xbox is no longer compatible with VS2017, and updates are required to have a network connection of any kind).
Christian Herzig
pthread_mutex_trylock() and by the way, pthread_mutex_lock() do not set errno.
Pthread-methods directly return error code as int. See related man-pages for
details.
Michael Sartain
This is a quick pass at adding Linux RealtimeKit thread priority support to SDL.
It allows me to bump the thread priority to high without root privileges or setting any caps, etc.
rtkit readme here:
http://git.0pointer.net/rtkit.git/tree/README
Most pthread functions return 0 on success and non-zero on error, but those
errors might be positive or negative, so checking for return values in the
Unix style, where errors are less than zero, is a bug.
Fixes Bugzilla #4039.
SDL now builds with gcc 7.2 with the following command line options:
-Wall -pedantic-errors -Wno-deprecated-declarations -Wno-overlength-strings --std=c99
Ian Abbott
I just spotted what I think is a bug in "src/thread/pthread/SDL_sysmutex.c" in the SDL_TryLockMutex function when FAKE_RECURSIVE_MUTEX is defined (for an implementation of Pthreads with no recursive mutex support). It calls pthread_mutex_lock instead of pthread_mutex_trylock, so it will block until the mutex is available instead of returning SDL_MUTEX_TIMEDOUT if it cannot lock the mutex immediately.
It's easier for Visual Studio users that want this information to turn it on
or live without it, than it is to explain why every debugger that isn't Visual
Studio crashes out here. Eventually SetThreadDescription() will be the thing
everyone uses anyhow.
Fixes Bugzilla #3645.
(and several others).
This is a bleeding edge API, added to Windows 10 Anniversary Edition (build
1607, specifically).
https://msdn.microsoft.com/en-us/library/windows/desktop/mt774976(v=vs.85).aspx
Nothing supports this yet, including WinDbg, Visual Studio, minidumps, etc,
so we still need to also use the RaiseException hack. But presumably tools
will use this API as a more robust and universal way to get thread names
sooner or later, so we'll start broadcasting to it now.
Sylvain
After a long time, I found out more clearly what was going wrong.
The native libraries should be built with a "APP_PLATFORM" as low as possible.
Ideally, APP_PLATFORM should be equals to the minSdkVersion of the AndroidManifest.xml
So that the application never runs on a lower APP_PLATFORM than it has been built for.
An additional good patch would be to write explicitly in "jni/Application.mk": APP_PLATFORM=android-10
(If no APP_PLATFORM is set, the "targetSdkVersion" of the AndroidManifest.xml is applied as an APP_PLATFORM to the native libraries. And currently, this is bad, because targetSdkVersion is 12, whereas minSdkLevel is 10.
And in fact, there is a warning from ndk: "Android NDK: WARNING: APP_PLATFORM android-12 is larger than android:minSdkVersion 10 in ./AndroidManifest.xml".)
to precise what happened in the initial reported test-case:
Let say the "c" code contains a call to "srand()".
with APP_PLATFORM=android-21, libSDL2.so contains a undef reference to "srand()".
with APP_PLATFORM=android-10, libSDL2.so contains a undef reference to "srand48()".
but srand() is missing on devices with APP_PLATFORM=android-10 (it was in fact replaced by srand48()).
So, if you build for android-21 (where srand() is available), you will really have a call to "srand()" and it will fail on android-10.
That was the issue. The path tried to fix this by in fact always calling srand48().
SDL patches that were applied are beneficial anyway, there are implicitly allowing they backward compatibility of using android-21 on a android-10 platform.
It can be helpful in case you want to target a higher APP_PLATFORM than minSdkVersion to have potentially access to more functions.
Eg you want to have access to GLES3 functions (or other) of "android-21". But, if dlopen() fails (on android-10), you do a fall-back to GLES2.
