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From: John Ogness <john.ogness@linutronix.de>
Date: Wed, 3 Mar 2021 11:15:14 +0100
Subject: [PATCH 01/29] 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: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-2-john.ogness@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/um/kernel/kmsg_dump.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -1,5 +1,6 @@
// 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 km
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 = {
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