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printk: nbcon: Add helper to assign priority based on CPU state

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Add a helper function to use the current state of the CPU to
determine which priority to assign to the printing context.

The EMERGENCY priority handling is added in a follow-up commit.
It will use a per-CPU variable.

Note: nbcon_device_try_acquire(), which is used by console
      drivers to acquire the nbcon console for non-printing
      activities, is hard-coded to always use NORMAL priority.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-20-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness 2024-08-20 08:35:45 +02:06 committed by Petr Mladek
parent fc400d5f63
commit 06683a6649
2 changed files with 21 additions and 0 deletions
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2
kernel/printk/internal.h
View File

@ -83,6 +83,7 @@ u64 nbcon_seq_read(struct console *con);
void nbcon_seq_force(struct console *con, u64 seq);
bool nbcon_alloc(struct console *con);
void nbcon_free(struct console *con);
enum nbcon_prio nbcon_get_default_prio(void);
/*
* Check if the given console is currently capable and allowed to print
@ -136,6 +137,7 @@ static inline u64 nbcon_seq_read(struct console *con) { return 0; }
static inline void nbcon_seq_force(struct console *con, u64 seq) { }
static inline bool nbcon_alloc(struct console *con) { return false; }
static inline void nbcon_free(struct console *con) { }
static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; }
static inline bool console_is_usable(struct console *con, short flags) { return false; }

19
kernel/printk/nbcon.c
View File

@ -973,6 +973,25 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)
return nbcon_context_exit_unsafe(ctxt);
}
/**
* nbcon_get_default_prio - The appropriate nbcon priority to use for nbcon
* printing on the current CPU
*
* Context: Any context.
* Return: The nbcon_prio to use for acquiring an nbcon console in this
* context for printing.
*
* The function is safe for reading per-CPU data in any context because
* preemption is disabled if the current CPU is in the panic state.
*/
enum nbcon_prio nbcon_get_default_prio(void)
{
if (this_cpu_in_panic())
return NBCON_PRIO_PANIC;
return NBCON_PRIO_NORMAL;
}
/**
* nbcon_alloc - Allocate and init the nbcon console specific data
* @con: Console to initialize