CircuitPython - a Python implementation for teaching coding with microcontrollers https://git.suspectdevices.com/suspect-devices/circuitpython/atom?h=master 2020-05-29T01:34:14+00:00 2020-05-29T01:34:14+00:00 Scott Shawcroft scott@tannewt.org 2020-05-29T01:29:11+00:00 urn:sha1:2fb4fa328946b07d90bd951d4a134ea8d31be7e8 From the change: // xtensa has more registers than an instruction can address. The 16 that // can be addressed are called the "window". When a function is called or // returns the window rotates. This allows for more efficient function calls // because ram doesn't need to be used. It's only used if the window wraps // around onto itself. At that point values are "spilled" to empty spots in // the stack that were set aside. When the window rotates back around (on // function return), the values are restored into the register from ram. // So, in order to read the values in the stack scan we must make sure all // of the register values we care about have been spilled to RAM. Luckily, // there is a HAL call to do it. There is a bit of a race condition here // because the register value could change after it's been restored but that // is unlikely to happen with a heap pointer while we do a GC. Fixes #2907