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

John Ogness
2021-02-18T09:40:02Z

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@linutronix.de

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(-)

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2.20.1