Date:   Thu, 25 Feb 2021 21:24:23 +0100
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Thomas Meyer <thomas@...3r.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-um@...ts.infradead.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
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        Pavel Tatashin <pasha.tatashin@...een.com>,
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        Sumit Garg <sumit.garg@...aro.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Wei Li <liwei391@...wei.com>, linuxppc-dev@...ts.ozlabs.org,
        kgdb-bugreport@...ts.sourceforge.net,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
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        Oleg Nesterov <oleg@...hat.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        linux-hyperv@...r.kernel.org
Subject: [PATCH next v3 00/15] printk: remove logbuf_lock

Hello,

Here is v3 of a series to remove @logbuf_lock, exposing the
ringbuffer locklessly to both readers and writers. v2 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_lock.

Removing @logbuf_lock required changing the semantics of the
kmsg_dumper callback in order to work locklessly. Since this
involved touching all the kmsg_dump users, we also decided [1] to
use this opportunity to clean up and clarify the kmsg_dump semantics
in general.

This series is based on next-20210225.

Changes since v2:

- use get_maintainer.pl to get the full list of developers that
  should at least see the changes in their respective areas

- do not disable interrupts in arch/um kmsg_dumper (because there is
  no need to)

- protect the mtd/mtdoops kmsg_dumper buffer against concurrent
  dumps

- update kerneldoc for kmsg_dump_get_line() (@len_out)

- remove ksmg_dump's @active flag

- change kmsg_dumper callback to:
  void (*dump)(enum kmsg_dump_reason reason);

- rename kmsg_dumper_iter to kmsg_dump_iter

- update kmsg_dumpers to use their own kmsg_dump_iter (and
  initialize it with kmsg_dump_rewind() if necessary)

John Ogness

[0] https://lkml.kernel.org/r/20210218081817.28849-1-john.ogness@linutronix.de
[1] https://lkml.kernel.org/r/YDeZAA08NKCHa4s%2F@alley

John Ogness (15):
  um: synchronize kmsg_dumper
  mtd: mtdoops: synchronize kmsg_dumper
  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: kmsg_dumper: remove @active field
  printk: introduce a kmsg_dump iterator
  printk: remove logbuf_lock
  printk: kmsg_dump: remove _nolock() variants
  printk: console: remove unnecessary safe buffer usage

 arch/powerpc/kernel/nvram_64.c             |  14 +-
 arch/powerpc/platforms/powernv/opal-kmsg.c |   3 +-
 arch/powerpc/xmon/xmon.c                   |   6 +-
 arch/um/kernel/kmsg_dump.c                 |  15 +-
 drivers/hv/vmbus_drv.c                     |   7 +-
 drivers/mtd/mtdoops.c                      |  20 +-
 fs/pstore/platform.c                       |   8 +-
 include/linux/kmsg_dump.h                  |  49 +--
 kernel/debug/kdb/kdb_main.c                |  10 +-
 kernel/printk/internal.h                   |   4 +-
 kernel/printk/printk.c                     | 456 ++++++++++-----------
 kernel/printk/printk_safe.c                |  27 +-
 12 files changed, 309 insertions(+), 310 deletions(-)

-- 
2.20.1

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