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printk: Add function to replay kernel log on consoles

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Add a generic function console_replay_all() for replaying
the kernel log on consoles, in any context. It would allow
viewing the logs on an unresponsive terminal via sysrq.

Reuse the existing code from console_flush_on_panic() for
resetting the sequence numbers, by introducing a new helper
function __console_rewind_all(). It is safe to be called
under console_lock().

Try to acquire lock on the console subsystem without waiting.
If successful, reset the sequence number to oldest available
record on all consoles and call console_unlock() which will
automatically flush the messages to the consoles.

Suggested-by: John Ogness <john.ogness@linutronix.de>
Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Shimoyashiki Taichi <taichi.shimoyashiki@sony.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sreenath Vijayan <sreenath.vijayan@sony.com>
Link: https://lore.kernel.org/r/90ee131c643a5033d117b556c0792de65129d4c3.1710220326.git.sreenath.vijayan@sony.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sreenath Vijayan
2024-03-13 15:50:52 +05:30
committed by Greg Kroah-Hartman
parent 25ca2d573e
commit 693f75b91a
2 changed files with 57 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/printk.h
+4
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@@ -195,6 +195,7 @@ void show_regs_print_info(const char *log_lvl);
extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
extern asmlinkage void dump_stack(void) __cold;
void printk_trigger_flush(void);
void console_replay_all(void);
#else
static inline __printf(1, 0)
int vprintk(const char *s, va_list args)
@@ -274,6 +275,9 @@ static inline void dump_stack(void)
static inline void printk_trigger_flush(void)
{
}
static inline void console_replay_all(void)
{
}
#endif
bool this_cpu_in_panic(void);