Commit 70411bf8 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

printk: Add is_printk_legacy_deferred() 



If printk has been explicitly deferred or is called from NMI
context, legacy console printing must be deferred to an irq_work
context. Introduce a helper function is_printk_legacy_deferred()
for a CPU to query if it must defer legacy console printing.

In follow-up commits this helper will be needed at other call
sites as well.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-24-john.ogness@linutronix.de


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent c158834b

kernel/printk/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -75,6 +75,7 @@ bool printk_percpu_data_ready(void); 
	} while (0)



void defer_console_output(void);

bool is_printk_legacy_deferred(void);



u16 printk_parse_prefix(const char *text, int *level,

			enum printk_info_flags *flags);
@@ -138,6 +139,7 @@ static inline bool console_is_usable(struct console *con, short flags) 
#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)



static inline bool printk_percpu_data_ready(void) { return false; }

static inline bool is_printk_legacy_deferred(void) { return false; }

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; }

kernel/printk/printk_safe.c

+10 −1
Original line number Diff line number Diff line
@@ -38,6 +38,15 @@ void __printk_deferred_exit(void) 
	__printk_safe_exit();

}



bool is_printk_legacy_deferred(void)

{

	/*

	 * The per-CPU variable @printk_context can be read safely in any

	 * context. CPU migration is always disabled when set.

	 */

	return (this_cpu_read(printk_context) || in_nmi());

}



asmlinkage int vprintk(const char *fmt, va_list args)

{

#ifdef CONFIG_KGDB_KDB
@@ -50,7 +59,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) 
	 * Use the main logbuf even in NMI. But avoid calling console

	 * drivers that might have their own locks.

	 */

	if (this_cpu_read(printk_context) || in_nmi())

	if (is_printk_legacy_deferred())

		return vprintk_deferred(fmt, args);



	/* No obstacles. */