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by nikital 2917 days ago
A restartable sequence is defined by a start and an end offset. If I write a restarable sequence in C I can't be absolutely sure that it's contiguous and I can't know where the commit instruction is...

Does it mean that I have to write it in assembly to make sure that I know where the sequence starts and where it ends?
2 comments
compudj 2916 days ago
Indeed the restartable sequence critical section needs to be written in assembly. The idea is to keep this complexity within public headers implementing the common operations as inline assembly for all supported architectures. You can see such operations already implemented for x86 as part of the rseq selftests here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...
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viraptor 2917 days ago
I think C lost it at: abort must be possible to call from any place in the critical block. Since you can't be sure the registers didn't spill on the stack, I don't think anything more than ASM would work.
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