[PATCH next v4 00/15] printk: remove logbuf_lock

John Ogness
2021-03-03T19:28:26Z

Hello,

Here is v4 of a series to remove @logbuf_lock, exposing the
ringbuffer locklessly to both readers and writers. v3 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. This series
adjusts all kmsg_dumpers and users of the kmsg_dump_get_*()
functions for the new semantics.

This series is based on next-20210303.

Changes since v3:

- disable interrupts in the arch/um kmsg_dumper

- reduce CONSOLE_LOG_MAX value from 4096 back to 1024 to revert
the increasd 3KiB static memory footprint

- change the kmsg_dumper() callback prototype back to how it
was because some dumpers need the registered object for
container_of() usage

- for kmsg_dump_get_line()/kmsg_dump_get_buffer() restrict the
minimal allowed sequence number to the cleared sequence number

John Ogness

[0] https://lore.kernel.org/lkml/20210225202438.28985-1-john.ogness@linutronix.de/

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
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 | 8 +-
arch/powerpc/xmon/xmon.c | 6 +-
arch/um/kernel/kmsg_dump.c | 13 +-
drivers/hv/vmbus_drv.c | 4 +-
drivers/mtd/mtdoops.c | 17 +-
fs/pstore/platform.c | 5 +-
include/linux/kmsg_dump.h | 47 ++--
kernel/debug/kdb/kdb_main.c | 10 +-
kernel/printk/internal.h | 4 +-
kernel/printk/printk.c | 464 +++++++++++++++++----------------
kernel/printk/printk_safe.c | 27 +-
11 files changed, 310 insertions(+), 295 deletions(-)

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2.20.1