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twizzler-operating-system / twizzler

The Twizzler Operating System
BSD 3-Clause "New" or "Revised" License
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Fix aarch64 context switch when compiled in release mode #137

Closed PandaZ3D closed 1 year ago

PandaZ3D commented 1 year ago

This patch fixes a bug in the context switch code for aarch64. The problem was that since the _old_thread var was "unused" when compiled in release mode the function would inline the assembly when a context switch happened. This is problematic since using x0/x1 which point to the arguments lose all meaning. We fixed this by explicitly using the arguments and assigning the thread save area to registers used in the assembly.

dbittman commented 1 year ago

Are you planning to, in the future, add some kind of SMP lock in there like the x86 code has?

PandaZ3D commented 1 year ago

Are you planning to, in the future, add some kind of SMP lock in there like the x86 code has?

Yes. The aarch64 port does not currently support SMP. So that would be one of the many things we would have to implement.