Re: [PATCH v3 2/2] livepatch: force transition process to finish

Pavel Machek
2017-11-06T11:11:08Z

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On Tue 2017-10-31 12:48:53, Miroslav Benes wrote:
> If a task sleeps in a set of patched functions uninterruptedly, it could
> block the whole transition process indefinitely. Thus it may be useful
> to clear its TIF_PATCH_PENDING to allow the process to finish.
>
> Admin can do that now by writing to force sysfs attribute in livepatch
> sysfs directory. TIF_PATCH_PENDING is then cleared for all tasks and the
> transition can finish successfully.
>
> Important note! Use wisely. Admin must be sure that it is safe to
> execute such action. This means that it must be checked that by doing so
> the consistency model guarantees are not violated.
>
> Signed-off-by: Miroslav Benes <mbenes@suse.cz>
> ---
> Documentation/ABI/testing/sysfs-kernel-livepatch | 10 +++++++++
> Documentation/livepatch/livepatch.txt | 24 +++++++++++++++------
> kernel/livepatch/core.c | 27 ++++++++++++++++++++++++
> kernel/livepatch/transition.c | 25 ++++++++++++++++++++++
> kernel/livepatch/transition.h | 1 +
> 5 files changed, 81 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch
> index 22f6267836c2..105f617008f1 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-livepatch
> +++ b/Documentation/ABI/testing/sysfs-kernel-livepatch
> @@ -42,6 +42,16 @@ Contact: live-patching@vger.kernel.org
> course of an existing transition. Writing 1 sends a signal to
> all remaining blocking tasks.
>
> +What: /sys/kernel/livepatch/<patch>/force
> +Date: Oct 2017
> +KernelVersion: 4.15.0
> +Contact: live-patching@vger.kernel.org
> +Description:
> + A writable attribute that allows administrator to affect the
> + course of an existing transition. Writing 1 clears
> + TIF_PATCH_PENDING flag of all tasks and thus forces the tasks to
> + the patched or unpatched state.
> +

NAK. Admin does not have chance to decide if this is safe or not.

Pavel

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