lib/uksched: Do not save/restore ECTX on coop thread switching #1570
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Since we only have cooperative scheduling at the moment, saving/restoring ECTX when thread switching is not necessary, since the ABI treats these registers as scratch registers and thread switching essentially happens through actual explicit function calls. On the other hand, this is obviously not the case with preemptive scheduling since thread switching can happen out of the blue, typically on a timer IRQ, so then ECTX saving/restoring is definetely necessary. But, again, we are only doing cooperative scheduling at the moment and this operation adds unnecessary overhead so throw it out. Signed-off-by: Sergiu Moga <[email protected]>
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Description of changes
Since we only have cooperative scheduling at the moment, saving/restoring ECTX when thread switching is not necessary, since the ABI treats these registers as scratch registers and thread switching essentially happens through actual explicit function calls.
On the other hand, this is obviously not the case with preemptive scheduling since thread switching can happen out of the blue, typically on a timer IRQ, so then ECTX saving/restoring is definetely necessary.
But, again, we are only doing cooperative scheduling at the moment and this operation adds unnecessary overhead so throw it out.