mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
synced 2025-01-15 11:47:47 +00:00
6b93bb41f6
The current console/printk subsystem is protected by a Big Kernel Lock, (aka console_lock) which has ill defined semantics and is more or less stateless. This puts severe limitations on the console subsystem and makes forced takeover and output in emergency and panic situations a fragile endeavour that is based on try and pray. The goal of non-BKL (nbcon) consoles is to break out of the console lock jail and to provide a new infrastructure that avoids the pitfalls and also allows console drivers to be gradually converted over. The proposed infrastructure aims for the following properties: - Per console locking instead of global locking - Per console state that allows to make informed decisions - Stateful handover and takeover As a first step, state is added to struct console. The per console state is an atomic_t using a 32bit bit field. Reserve state bits, which will be populated later in the series. Wire it up into the console register/unregister functionality. It was decided to use a bitfield because using a plain u32 with mask/shift operations resulted in uncomprehensible code. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-2-john.ogness@linutronix.de
116 lines
3.2 KiB
C
116 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/*
|
|
* internal.h - printk internal definitions
|
|
*/
|
|
#include <linux/percpu.h>
|
|
#include <linux/console.h>
|
|
|
|
#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
|
|
void __init printk_sysctl_init(void);
|
|
int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
|
|
void *buffer, size_t *lenp, loff_t *ppos);
|
|
#else
|
|
#define printk_sysctl_init() do { } while (0)
|
|
#endif
|
|
|
|
#ifdef CONFIG_PRINTK
|
|
|
|
#ifdef CONFIG_PRINTK_CALLER
|
|
#define PRINTK_PREFIX_MAX 48
|
|
#else
|
|
#define PRINTK_PREFIX_MAX 32
|
|
#endif
|
|
|
|
/*
|
|
* the maximum size of a formatted record (i.e. with prefix added
|
|
* per line and dropped messages or in extended message format)
|
|
*/
|
|
#define PRINTK_MESSAGE_MAX 2048
|
|
|
|
/* the maximum size allowed to be reserved for a record */
|
|
#define PRINTKRB_RECORD_MAX 1024
|
|
|
|
/* Flags for a single printk record. */
|
|
enum printk_info_flags {
|
|
LOG_NEWLINE = 2, /* text ended with a newline */
|
|
LOG_CONT = 8, /* text is a fragment of a continuation line */
|
|
};
|
|
|
|
__printf(4, 0)
|
|
int vprintk_store(int facility, int level,
|
|
const struct dev_printk_info *dev_info,
|
|
const char *fmt, va_list args);
|
|
|
|
__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
|
|
__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
|
|
|
|
bool printk_percpu_data_ready(void);
|
|
|
|
#define printk_safe_enter_irqsave(flags) \
|
|
do { \
|
|
local_irq_save(flags); \
|
|
__printk_safe_enter(); \
|
|
} while (0)
|
|
|
|
#define printk_safe_exit_irqrestore(flags) \
|
|
do { \
|
|
__printk_safe_exit(); \
|
|
local_irq_restore(flags); \
|
|
} while (0)
|
|
|
|
void defer_console_output(void);
|
|
|
|
u16 printk_parse_prefix(const char *text, int *level,
|
|
enum printk_info_flags *flags);
|
|
|
|
void nbcon_init(struct console *con);
|
|
void nbcon_cleanup(struct console *con);
|
|
|
|
#else
|
|
|
|
#define PRINTK_PREFIX_MAX 0
|
|
#define PRINTK_MESSAGE_MAX 0
|
|
#define PRINTKRB_RECORD_MAX 0
|
|
|
|
/*
|
|
* In !PRINTK builds we still export console_sem
|
|
* semaphore and some of console functions (console_unlock()/etc.), so
|
|
* printk-safe must preserve the existing local IRQ guarantees.
|
|
*/
|
|
#define printk_safe_enter_irqsave(flags) local_irq_save(flags)
|
|
#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
|
|
|
|
static inline bool printk_percpu_data_ready(void) { return false; }
|
|
static inline void nbcon_init(struct console *con) { }
|
|
static inline void nbcon_cleanup(struct console *con) { }
|
|
|
|
#endif /* CONFIG_PRINTK */
|
|
|
|
/**
|
|
* struct printk_buffers - Buffers to read/format/output printk messages.
|
|
* @outbuf: After formatting, contains text to output.
|
|
* @scratchbuf: Used as temporary ringbuffer reading and string-print space.
|
|
*/
|
|
struct printk_buffers {
|
|
char outbuf[PRINTK_MESSAGE_MAX];
|
|
char scratchbuf[PRINTKRB_RECORD_MAX];
|
|
};
|
|
|
|
/**
|
|
* struct printk_message - Container for a prepared printk message.
|
|
* @pbufs: printk buffers used to prepare the message.
|
|
* @outbuf_len: The length of prepared text in @pbufs->outbuf to output. This
|
|
* does not count the terminator. A value of 0 means there is
|
|
* nothing to output and this record should be skipped.
|
|
* @seq: The sequence number of the record used for @pbufs->outbuf.
|
|
* @dropped: The number of dropped records from reading @seq.
|
|
*/
|
|
struct printk_message {
|
|
struct printk_buffers *pbufs;
|
|
unsigned int outbuf_len;
|
|
u64 seq;
|
|
unsigned long dropped;
|
|
};
|
|
|
|
bool other_cpu_in_panic(void);
|