[PATCH printk-rework 00/14] printk: remove logbuf_lock

[John Ogness]

Hello,

Here is v2 of a series to remove @logbuf_lock, exposing the
ringbuffer locklessly to both readers and writers. v1 is here [0].

Since @logbuf_lock was protecting much more than just the
ringbuffer, this series clarifies and cleans up the various
protections using comments, lockless accessors, atomic types, and a
new finer-grained @syslog_log.

Changes since v1:

- handle the syslog_print_all() size calculation issue in a separate
  patch (patch 1)

- use a local printk_info for find_first_fitting_seq()

- define CONSOLE_LOG_MAX in printk.c instead of printk.h since it is
  not used outside of printk.c

- increase CONSOLE_LOG_MAX to 4096 to support long multi-line
  records

- add a wrapper function read_syslog_seq_irq() for getting a
  consistent @syslog_seq value (only used in do_syslog())

- drop the "hv: synchronize kmsg_dumper" patch

- in "remove logbuf_lock" only change to safe buffer usage

- fixup safe buffer usage and redundance in separate patches
  (patches 13 and 14)

- update comments and commit messages as requested

John Ogness

[0] https://lkml.kernel.org/r/20210126211551.26536-1-john.ogness@xxxxxxxxxxxxx

John Ogness (14):
  printk: limit second loop of syslog_print_all
  printk: kmsg_dump: remove unused fields
  printk: refactor kmsg_dump_get_buffer()
  printk: consolidate kmsg_dump_get_buffer/syslog_print_all code
  printk: introduce CONSOLE_LOG_MAX for improved multi-line support
  printk: use seqcount_latch for clear_seq
  printk: use atomic64_t for devkmsg_user.seq
  printk: add syslog_lock
  printk: introduce a kmsg_dump iterator
  um: synchronize kmsg_dumper
  printk: remove logbuf_lock
  printk: kmsg_dump: remove _nolock() variants
  printk: kmsg_dump: use kmsg_dump_rewind
  printk: console: remove unnecessary safe buffer usage

 arch/powerpc/kernel/nvram_64.c             |  12 +-
 arch/powerpc/platforms/powernv/opal-kmsg.c |   3 +-
 arch/powerpc/xmon/xmon.c                   |   6 +-
 arch/um/kernel/kmsg_dump.c                 |  13 +-
 drivers/hv/vmbus_drv.c                     |   5 +-
 drivers/mtd/mtdoops.c                      |   5 +-
 fs/pstore/platform.c                       |   5 +-
 include/linux/kmsg_dump.h                  |  52 +--
 kernel/debug/kdb/kdb_main.c                |  10 +-
 kernel/printk/internal.h                   |   4 +-
 kernel/printk/printk.c                     | 454 +++++++++++----------
 kernel/printk/printk_safe.c                |  29 +-
 12 files changed, 298 insertions(+), 300 deletions(-)

-- 
2.20.1