Messages in this thread | | | From | John Ogness <> | Subject | [PATCH printk v4 0/8] printk: cleanup buffer handling | Date | Thu, 5 Jan 2023 11:43:27 +0106 |
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Hi,
This is v4 of a series to cleanup console buffer handling and prepare for code sharing with the upcoming threaded/atomic consoles. v3 is here [0].
The main purpose of the series is to introduce two new lockless functions to handle reading and formatting of printk messages. These functions can then be used from any context, which is important for the upcoming threaded/atomic consoles. The series also helps to cleanup some of the internal printk interfaces and cleanly separate formatting code from outputting code.
Some changes in this version were not part of the feedback. However, from the discussions and examples I decided that some of the names I had previously chosen were not appropriate. Particularly, structs, variables, and functions should only use the "console_" prefix if it is console-specific. Things that are used for general printk processing should use a "printk_" prefix. This makes the diff to v3 rather large, even though the "real code" has only minor changes.
@Petr: Like with v3, this version uses a wrapper struct for the message metadata to avoid clobbering. Making the message formatting code robust enough to handle metadata clobbering was too complex (particularly with the dropped tracking).
Changes since v3:
- Provide a detailed explanation in the commit message about why message metadata is put into a wrapper struct instead of the buffer struct.
- Reorder stack variable definitions so that static variables are at the top and separated from non-static variables. IMHO it is important to clearly see which of the variables are static.
- Drop a previous coding-style change from a line not related to this series.
- In console_prepend_dropped() make sure the buffer is large enough for the dropped message and at least PREFIX_MAX of the current message.
- Define the PREFIX_MAX macro for !CONFIG_PRINTK in internal.h because console_prepend_dropped() now needs it.
- Rename various functions, structs, fields, and macros:
console_get_next_message() -> printk_get_next_message()
struct console_buffers -> struct printk_buffers
struct console_message -> struct printk_message
console_message.cbufs -> printk_message.pbufs
console_message.outbuf_seq -> printk_message.seq
LOG_LINE_MAX -> PRINTKRB_RECORD_MAX
PREFIX_MAX -> PRINTK_PREFIX_MAX
CONSOLE_LOG_MAX and CONSOLE_EXT_LOG_MAX -> PRINTK_MESSAGE_MAX
- Adjust the values of string limit macros. This is explained in detail in the commit message.
- Replace @buf and @text_buf in struct devkmsg_user with struct printk_buffers.
- Replace message formatting code in devkmsg_read() with printk_get_next_message().
- Define all printk_message structs on the stack.
John Ogness
[0] https://lore.kernel.org/lkml/20221221202704.857925-1-john.ogness@linutronix.de
John Ogness (6): printk: move size limit macros into internal.h printk: introduce struct printk_buffers printk: introduce printk_get_next_message() and printk_message printk: introduce console_prepend_dropped() for dropped messages printk: use printk_buffers for devkmsg printk: adjust string limit macros
Thomas Gleixner (2): console: Use BIT() macros for @flags values console: Document struct console
include/linux/console.h | 100 +++++++++---- include/linux/printk.h | 2 - kernel/printk/internal.h | 45 ++++++ kernel/printk/printk.c | 293 +++++++++++++++++++++++---------------- 4 files changed, 288 insertions(+), 152 deletions(-)
base-commit: 6b2b0d839acaa84f05a77184370f793752e786e9 -- 2.30.2
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