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    SubjectRe: [PATCH 0/9] Refactoring exit
    Al Viro <viro@zeniv.linux.org.uk> writes:

    > On Thu, Jun 24, 2021 at 01:57:35PM -0500, Eric W. Biederman wrote:
    >
    >> So far the code has been lightly tested, and the descriptions of some
    >> of the patches are a bit light, but I think this shows the direction
    >> I am aiming to travel for sorting out exit(2) and exit_group(2).
    >
    > FWIW, here's the current picture for do_exit(), aside of exit(2) and do_exit_group():
    >
    > 1) stuff that is clearly oops-like -
    > alpha:die_if_kernel() alpha:do_entUna() alpha:do_page_fault() arm:oops_end()
    > arm:__do_kernel_fault() arm64:die() arm64:die_kernel_fault() csky:alignment()
    > csky:die() csky:no_context() h8300:die() h8300:do_page_fault() hexagon:die()
    > ia64:die() i64:ia64_do_page_fault() m68k:die_if_kernel() m68k:send_fault_sig()
    > microblaze:die() mips:die() nds32:handle_fpu_exception() nds32:die()
    > nds32:unhandled_interruption() nds32:unhandled_exceptions() nds32:do_revinsn()
    > nds32:do_page_fault() nios:die() openrisc:die() openrisc:do_page_fault()
    > parisc:die_if_kernel() ppc:oops_end() riscv:die() riscv:die_kernel_fault()
    > s390:die() s390:do_no_context() s390:do_low_address() sh:die()
    > sparc32:die_if_kernel() sparc32:do_sparc_fault() sparc64:die_if_kernel()
    > x86:rewind_stack_do_exit() xtensa:die() xtensa:bad_page_fault()
    > We really do not want ptrace anywhere near any of those and we do not want
    > any of that to return; this shit would better be handled right there and
    > there - no "post a fatal signal" would do.

    Thanks that makes a good start for digging into these.

    I think the distinction I would make is:
    - If the kernel is broken use do_task_dead.
    - Otherwise cleanup the semantics by using start_group_exit,
    start_task_exit or by just cleaning up the code.


    Looking at the reboot case it looks like we the code
    should have become do_group_exit in 2.5. I have a suspicion
    we have a bunch of similar cases that want to terminate the
    entire process, but we simply never updated to deal with
    multi-thread processes.

    I suspect in the reboot case panic if machine_halt or
    or machine_power_off fails is more likely the correct
    handling. But we do have funny semantics sometimes.

    I will see what I can do to expand my patchset to handle all of these
    various callers of do_exit.

    Eric

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