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SubjectRe: [PATCH v4 0/4] printk: replace ringbuffer
On 2020-07-08, Petr Mladek <> wrote:
> OK, I think that we are ready to try this in linux-next.
> I am going to push it there via printk/linux.git.
> [...]
> Of course, there are still many potential problems. The following comes
> to my mind:
> [...]
> + Debugging tools accessing the buffer directly would need to
> understand the new structure. Fortunately John provided
> patches for the most prominent ones.

The next series in the printk-rework (move LOG_CONT handling from
writers to readers) makes some further changes that, while not
incompatible, could affect the output of existing tools. It may be a
good idea to let the new ringbuffer sit in linux-next until the next
series has been discussed/reviewed/merged. After the next series,
everything will be in place (with regard to userspace tools) to finish
the rework.

As reminder, here are all the steps planned for the full rework:

1. replace ringbuffer
2. implement NMI-safe LOG_CONT (i.e. move handling to readers)
3. remove logbuf_lock
4. remove safe buffers
5. implement per-console printing kthreads
6. implement emergency mode and write_atomic() support
7. implement write_atomic() for 8250 UART

Some of the steps may be combined into a single series if the changes
are not too dramatic.

John Ogness

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