Yeah I'm thinking the OS halts the CPU side of the render and, say, stuffs an errno into a register after the routine so the CPU can see what happened and recover. If I were writing a program that required a minimum frame rate and I missed multiple frames, it would probably be nicer for the user if I displayed a message that I was just unable to write a frame at the required speed and quit rather than screen tear and frustrate the user.
A similar situation happens if my NIC/kernel buffers are to overloaded to send the packets I need out. Instead I can try in vain to push packets out and have almost no understanding how many packets the OS is dropping just to keep up. Media standards like RTCP were designed around scenarios like these, but that itself is complexity we wouldn't need if the OS could notify the application when their packet writes failed.
This kind of flexibility right now is really difficult because most OSs try to pretend as hard as possible that everything happens sequentially. This is just about opening up more complete abstractions to the programmer.
A similar situation happens if my NIC/kernel buffers are to overloaded to send the packets I need out. Instead I can try in vain to push packets out and have almost no understanding how many packets the OS is dropping just to keep up. Media standards like RTCP were designed around scenarios like these, but that itself is complexity we wouldn't need if the OS could notify the application when their packet writes failed.
This kind of flexibility right now is really difficult because most OSs try to pretend as hard as possible that everything happens sequentially. This is just about opening up more complete abstractions to the programmer.