[Android] Stop calling eglSwapBuffers immediately. #4252
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Since we're seeing ANRs at SCREEN_OFF where the rasterizer thread appears to be hanging during eglSwapBuffers, this change attempts to avoid those ANRs by immediately skip calls to eglSwapBuffers when a surfaceDestroyed event is received, until a the next SurfaceCreated. Since Cobalt uses GameActivity, those are received in calls to OnNativeWindowDestroyed respectively OnNativeWindowCreated. b/225209442
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Cherry-pick of #3076. I believe this deserves a chance. |
| @@ -41,6 +41,9 @@ | |||
| namespace starboard { | |||
| namespace android { | |||
| namespace shared { | |||
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| atomic_bool g_block_swapbuffers; | |||
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Does this need to be an atomic ? It's only written to from Android UI thread and read in renderer thread, it can just be a bool ?
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It has to be atomic exactly because it's read from a different thread than from where it's written. It ensures that it's not read while being written and potentially only partially written, in addition to using memory barriers to make sure it's not using a stale (cached) value.
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But there are no memory barriers here. Just making it atomic doesn't guarantee it's correctly reflected between threads and cores. If you want to absolutely ensure it's correct, just use a lock.
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The load() and store() of atomic_bool that are used to access it include barriers as needed.
See starboard/common/atomic.h lines 390 and 392.
Since we're seeing ANRs at SCREEN_OFF where the rasterizer thread appears to be hanging during eglSwapBuffers, this change attempts to avoid those ANRs by immediately skip calls to eglSwapBuffers when a surfaceDestroyed event is received, until a the next SurfaceCreated. Since Cobalt uses GameActivity, those are received in calls to OnNativeWindowDestroyed respectively OnNativeWindowCreated.
b/225209442