Commit 06683a66 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
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printk: nbcon: Add helper to assign priority based on CPU state 



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: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-20-john.ogness@linutronix.de


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent fc400d5f

kernel/printk/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -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; }

kernel/printk/nbcon.c

+19 −0
Original line number Diff line number Diff line
@@ -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