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um: synchronize kmsg_dumper

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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
This commit is contained in:
John Ogness 2021-03-03 11:15:14 +01:00 committed by Petr Mladek
parent b2bec7d8a4
commit fdd2c1f4e2
1 changed files with 8 additions and 0 deletions
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8
arch/um/kernel/kmsg_dump.c
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@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0 // SPDX-License-Identifier: GPL-2.0
#include <linux/kmsg_dump.h> #include <linux/kmsg_dump.h>
#include <linux/spinlock.h>
#include <linux/console.h> #include <linux/console.h>
#include <linux/string.h> #include <linux/string.h>
#include <shared/init.h> #include <shared/init.h>
@ -9,8 +10,10 @@
static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
enum kmsg_dump_reason reason) enum kmsg_dump_reason reason)
{ {
static DEFINE_SPINLOCK(lock);
static char line[1024]; static char line[1024];
struct console *con; struct console *con;
unsigned long flags;
size_t len = 0; size_t len = 0;
/* only dump kmsg when no console is available */ /* only dump kmsg when no console is available */
@ -29,11 +32,16 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
if (con) if (con)
return; return;
if (!spin_trylock_irqsave(&lock, flags))
return;
printf("kmsg_dump:\n"); printf("kmsg_dump:\n");
while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) { while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
line[len] = '\0'; line[len] = '\0';
printf("%s", line); printf("%s", line);
} }
spin_unlock_irqrestore(&lock, flags);
} }
static struct kmsg_dumper kmsg_dumper = { static struct kmsg_dumper kmsg_dumper = {