Contributors: 16
Author Tokens Token Proportion Commits Commit Proportion
Sergey Senozhatsky 42 24.14% 1 4.17%
Petr Mladek 37 21.26% 3 12.50%
Sebastian Andrzej Siewior 26 14.94% 1 4.17%
John Ogness 26 14.94% 6 25.00%
Russell King 14 8.05% 1 4.17%
Rasmus Villemoes 6 3.45% 1 4.17%
Andrew Morton 4 2.30% 2 8.33%
Steven Rostedt 3 1.72% 1 4.17%
Jason Wessel 3 1.72% 1 4.17%
Peter Zijlstra 3 1.72% 1 4.17%
Tejun Heo 2 1.15% 1 4.17%
Thomas Gleixner 2 1.15% 1 4.17%
Song Muchun 2 1.15% 1 4.17%
Sasha Levin 2 1.15% 1 4.17%
Robert P. J. Day 1 0.57% 1 4.17%
Matt Mackall 1 0.57% 1 4.17%
Total 174 24 
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// 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);
}

void __printk_deferred_enter(void)
{
	cant_migrate();
	__printk_safe_enter();
}

void __printk_deferred_exit(void)
{
	cant_migrate();
	__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 (force_legacy_kthread() ||
		this_cpu_read(printk_context) ||
		in_nmi());
}

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 (is_printk_legacy_deferred())
		return vprintk_deferred(fmt, args);

	/* No obstacles. */
	return vprintk_default(fmt, args);
}
EXPORT_SYMBOL(vprintk);