Restartable sequences in glibc

The code for a restartable sequence critical section sits squarely within a single inline asm. So there is no way one could "call" a data manipulation library from the inline asm without an explicit call, which would move the instruction pointer outside of the critical section, and is not at all a supported use-case.

So I really don't think the scenario you have in mind can realistically happen with the current rseq ABI.