[PATCH v5 0/4] printk: replace ringbuffer

[John Ogness]

Hello,

Here is a v5 for the first series to rework the printk
subsystem. The v4 is here [0]. This first series
only replaces the existing ringbuffer implementation. No locking
is removed. The semantics/behavior of printk are kept the same
except for a minor optimization that is reverted (patch 3).

RFC patches for various userspace tools to dump the kernel log
are available: crash [1], makedumpfile [2], kexec-tools [3].

This series is based on v5.8-rc4.

The list of changes since v4:

printk_ringbuffer
=================

- added new prb_first_valid_seq() for readers to retrieve the
  oldest valid sequence number

- prb_first_seq(): now static

printk.c
========

- devkmsg_read(): fixed returning EPIPE on buffer wrap [4]

- setup_log_buf(): fixed printk conversion specifier [5]

- replace all prb_first_seq() usage with the new
  prb_first_valid_seq() (because that is what the readers are
  actually interested in)

[0] https://lkml.kernel.org/r/20200707145932.8752-1-john.ogness@xxxxxxxxxxxxx
[1] https://github.com/Linutronix/crash.git (printk branch)
[2] https://github.com/Linutronix/makedumpfile.git (printk branch)
[3] https://github.com/Linutronix/kexec-tools.git (printk branch)
[4] https://lkml.kernel.org/r/87zh89kkek.fsf@xxxxxxxxxxxxxxxxxxxxx
[5] https://lkml.kernel.org/r/87r1tmcfhf.fsf@xxxxxxxxxxxxxxxxxxxxx

John Ogness (4):
  crash: add VMCOREINFO macro to define offset in a struct declared by
    typedef
  printk: add lockless ringbuffer
  Revert "printk: lock/unlock console only for new logbuf entries"
  printk: use the lockless ringbuffer

 include/linux/crash_core.h        |    3 +
 kernel/printk/Makefile            |    1 +
 kernel/printk/printk.c            |  950 ++++++++--------
 kernel/printk/printk_ringbuffer.c | 1687 +++++++++++++++++++++++++++++
 kernel/printk/printk_ringbuffer.h |  399 +++++++
 5 files changed, 2586 insertions(+), 454 deletions(-)
 create mode 100644 kernel/printk/printk_ringbuffer.c
 create mode 100644 kernel/printk/printk_ringbuffer.h

-- 
2.20.1