[linux-2.6-block.git] / kernel / printk / printk_safe.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * printk_safe.c - Safe printk for printk-deadlock-prone contexts
 */

#include <linux/preempt.h>
#include <linux/kdb.h>
#include <linux/smp.h>
#include <linux/cpumask.h>
#include <linux/printk.h>
#include <linux/kprobes.h>

#include "internal.h"

static DEFINE_PER_CPU(int, printk_context);

/* Can be preempted by NMI. */
void __printk_safe_enter(void)
{
	this_cpu_inc(printk_context);
}

/* Can be preempted by NMI. */
void __printk_safe_exit(void)
{
	this_cpu_dec(printk_context);
}

asmlinkage int vprintk(const char *fmt, va_list args)
{
#ifdef CONFIG_KGDB_KDB
	/* Allow to pass printk() to kdb but avoid a recursion. */
	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
		return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
#endif

	/*
	 * 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()) {
		int len;

		len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
		defer_console_output();
		return len;
	}

	/* No obstacles. */
	return vprintk_default(fmt, args);
}
EXPORT_SYMBOL(vprintk);
Commit	Line	Data
1ccea77e	1	// SPDX-License-Identifier: GPL-2.0-or-later
42a0bb3f	2	/*
099f1c84	3	* printk_safe.c - Safe printk for printk-deadlock-prone contexts
42a0bb3f PM	4	*/
	5
	6	#include <linux/preempt.h>
2a9e5ded	7	#include <linux/kdb.h>
42a0bb3f PM	8	#include <linux/smp.h>
42a0bb3f PM	9	#include <linux/cpumask.h>
42a0bb3f	10	#include <linux/printk.h>
b0f51883	11	#include <linux/kprobes.h>
42a0bb3f PM	12
	13	#include "internal.h"
	14
099f1c84 SS	15	static DEFINE_PER_CPU(int, printk_context);
099f1c84 SS	16
099f1c84 SS	17	/* Can be preempted by NMI. */
	18	void __printk_safe_enter(void)
	19	{
	20	this_cpu_inc(printk_context);
	21	}
	22
	23	/* Can be preempted by NMI. */
	24	void __printk_safe_exit(void)
	25	{
	26	this_cpu_dec(printk_context);
	27	}
	28
28e1745b	29	asmlinkage int vprintk(const char *fmt, va_list args)
099f1c84	30	{
2a9e5ded PM	31	#ifdef CONFIG_KGDB_KDB
	32	/* Allow to pass printk() to kdb but avoid a recursion. */
	33	if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
	34	return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
	35	#endif
	36
03fc7f9c	37	/*
996e9666	38	* Use the main logbuf even in NMI. But avoid calling console
03fc7f9c PM	39	* drivers that might have their own locks.
03fc7f9c PM	40	*/
85e3e7fb	41	if (this_cpu_read(printk_context) \|\| in_nmi()) {
03fc7f9c PM	42	int len;
03fc7f9c PM	43
74caba7f	44	len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
03fc7f9c PM	45	defer_console_output();
	46	return len;
	47	}
	48
719f6a70	49	/* No obstacles. */
099f1c84 SS	50	return vprintk_default(fmt, args);
099f1c84 SS	51	}
6262e1b9	52	EXPORT_SYMBOL(vprintk);