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.
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
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.
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
