Commit fdd2c1f4 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

um: synchronize kmsg_dumper 



The kmsg_dumper can be called from any context and CPU, possibly
from multiple CPUs simultaneously. Since a static buffer is used
to retrieve the kernel logs, this buffer must be protected against
simultaneous dumping. Skip dumping if another context is already
dumping.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-2-john.ogness@linutronix.de
parent b2bec7d8

arch/um/kernel/kmsg_dump.c

+8 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <linux/kmsg_dump.h>

#include <linux/spinlock.h>

#include <linux/console.h>

#include <linux/string.h>

#include <shared/init.h>
@@ -9,8 +10,10 @@ 
static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,

				enum kmsg_dump_reason reason)

{

	static DEFINE_SPINLOCK(lock);

	static char line[1024];

	struct console *con;

	unsigned long flags;

	size_t len = 0;



	/* only dump kmsg when no console is available */
@@ -29,11 +32,16 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, 
	if (con)

		return;



	if (!spin_trylock_irqsave(&lock, flags))

		return;



	printf("kmsg_dump:\n");

	while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {

		line[len] = '\0';

		printf("%s", line);

	}



	spin_unlock_irqrestore(&lock, flags);

}



static struct kmsg_dumper kmsg_dumper = {