On Sat, Nov 02, 2024 at 10:58:42PM +0100, Florian Weimer wrote:

QEMU hints towards further problems (in linux-user/syscall.c):

    case TARGET_NR_set_robust_list:
    case TARGET_NR_get_robust_list:
        /* The ABI for supporting robust futexes has userspace pass
         * the kernel a pointer to a linked list which is updated by
         * userspace after the syscall; the list is walked by the kernel
         * when the thread exits. Since the linked list in QEMU guest
         * memory isn't a valid linked list for the host and we have
         * no way to reliably intercept the thread-death event, we can't
         * support these. Silently return ENOSYS so that guest userspace
         * falls back to a non-robust futex implementation (which should
         * be OK except in the corner case of the guest crashing while
         * holding a mutex that is shared with another process via
         * shared memory).
         */
        return -TARGET_ENOSYS;

I don't think we can sanely fix that. Can't QEMU track the robust thing
itself and use waitpid() to discover the thread is gone and fudge things
from there?