Messages in this thread | | | From | John Ogness <> | Subject | [PATCH next v2 0/3] printk: remove logbuf_lock | Date | Tue, 1 Dec 2020 21:59:38 +0106 |
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Hello,
Here is a v2 of the next series for the printk-rework. It removes the @logbuf_lock. v1 is here [0]. Since this lock protected more than just the ringbuffer, a new finer-grained @syslog_lock is introduced.
With this series, vprintk_store() becomes lockless.
A consequence of this locklessness is that a buffer for temporary sprint space is no longer available. To get around this, vsnprintf() is used to determine the full length to reserve in the ringbuffer and then the message is directly sprint'ed to the reserved space.
Since the sprint'ed message may include syslog prefix and newline (both of which get stripped), there will be some bytes of wasted space per message. This space could be reclaimed by introducing a "trimming function" to the ringbuffer, which could reduce the size of a reserved data block if no newer block is reserved. However, such a function is not part of this series.
This series falls in line with the printk-rework plan as presented [1] at Linux Plumbers in Lisbon 2019.
The series is based on next-20201201.
John Ogness
[0] https://lkml.kernel.org/r/20200922153816.5883-1-john.ogness@linutronix.de [1] https://linuxplumbersconf.org/event/4/contributions/290/attachments/276/463/lpc2019_jogness_printk.pdf (slide 23)
John Ogness (3): printk: inline log_output(),log_store() in vprintk_store() printk: change @clear_seq to atomic64_t printk: remove logbuf_lock, add syslog_lock
include/linux/printk.h | 1 + kernel/printk/internal.h | 4 +- kernel/printk/printk.c | 411 ++++++++++++++++++------------------ kernel/printk/printk_safe.c | 18 +- 4 files changed, 212 insertions(+), 222 deletions(-)
-- 2.20.1
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