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    SubjectRe: [RFC PATCH for 4.17 02/21] rseq: Introduce restartable sequences system call (v12)
    On Wed, Mar 28, 2018 at 11:14:05AM -0400, Mathieu Desnoyers wrote:

    > > If at all possible I would make it SIGSEGV when issueing SYSCALL()s from
    > > within an RSEQ.
    >
    > What's the goal there ? rseq critical sections can technically do system calls
    > if they wish. Why prevent this ?

    This all started as a way to do 'small' _fast_ per-cpu ops, System calls
    do NOT fit in that pattern. If you're willing to do a system calls the
    cost of atomics is not a problem.

    > How would you handle signal handlers that issue system calls while nested
    > on top of a rseq critical section in the userspace thread ? SIGSEGV on
    > SYSCALLs will break this case.

    Have the rseq thing aborted prior to delivering the signal ?

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