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    Subject[RFC PATCH for 5.8 0/4] rseq cpu_id ABI fix
    Date
    Hi,

    Recent integration of rseq into glibc unearthed an issue with inaccurate
    cpu_id field for newly created tasks. This series includes a fix for the
    underlying issue (meant to be backported to stable), as well as new rseq
    flags to let user-space know that the kernel implements this fix, so
    glibc and other rseq users can use this flag to know whether they can
    safely use rseq without risk of corrupting their per-cpu data. This new
    flag could either be added only to the master branch (no stable
    backport) or backported to stable, depending on what seems the most
    appropriate.

    This is an RFC aiming for quick inclusion into the Linux kernel, unless
    we prefer reverting the entire rseq glibc integration and try again in 6
    months. Their upcoming release is on August 3rd, so we need to take a
    decision on this matter quickly.

    Thanks,

    Mathieu

    Mathieu Desnoyers (4):
    sched: Fix unreliable rseq cpu_id for new tasks
    rseq: Introduce RSEQ_FLAG_REGISTER
    rseq: Introduce RSEQ_FLAG_RELIABLE_CPU_ID
    rseq: selftests: Expect reliable cpu_id field

    include/uapi/linux/rseq.h | 15 +++++-
    kernel/rseq.c | 81 ++++++++++++++++-------------
    kernel/sched/core.c | 2 +
    tools/testing/selftests/rseq/rseq.c | 10 +++-
    4 files changed, 71 insertions(+), 37 deletions(-)

    --
    2.17.1

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