From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Jeff Dike <jdike@addtoit.com>,
Richard Weinberger <richard@nod.at>,
Anton Ivanov <anton.ivanov@cambridgegreys.com>,
Thomas Meyer <thomas@m3y3r.de>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
linux-um@lists.infradead.org
Subject: [PATCH next v3 01/15] um: synchronize kmsg_dumper
Date: Thu, 25 Feb 2021 21:24:24 +0100 [thread overview]
Message-ID: <20210225202438.28985-2-john.ogness@linutronix.de> (raw)
In-Reply-To: <20210225202438.28985-1-john.ogness@linutronix.de>
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>
---
arch/um/kernel/kmsg_dump.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index 6516ef1f8274..4869e2cc787c 100644
--- 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>
@@ -9,6 +10,7 @@
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;
size_t len = 0;
@@ -29,11 +31,16 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
if (con)
return;
+ if (!spin_trylock(&lock))
+ return;
+
printf("kmsg_dump:\n");
while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
line[len] = '\0';
printf("%s", line);
}
+
+ spin_unlock(&lock);
}
static struct kmsg_dumper kmsg_dumper = {
--
2.20.1
next prev parent reply other threads:[~2021-02-25 20:25 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 20:24 [PATCH next v3 00/15] printk: remove logbuf_lock John Ogness
2021-02-25 20:24 ` John Ogness [this message]
2021-03-01 16:16 ` [PATCH next v3 01/15] um: synchronize kmsg_dumper Petr Mladek
2021-03-01 16:57 ` Petr Mladek
2021-03-02 8:06 ` John Ogness
2021-03-02 10:12 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 02/15] mtd: mtdoops: " John Ogness
2021-03-01 12:13 ` Petr Mladek
2021-03-02 10:45 ` John Ogness
2021-03-02 12:48 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 03/15] printk: limit second loop of syslog_print_all John Ogness
2021-02-25 20:24 ` [PATCH next v3 04/15] printk: kmsg_dump: remove unused fields John Ogness
2021-02-25 20:24 ` [PATCH next v3 05/15] printk: refactor kmsg_dump_get_buffer() John Ogness
2021-02-25 20:24 ` [PATCH next v3 06/15] printk: consolidate kmsg_dump_get_buffer/syslog_print_all code John Ogness
2021-02-25 20:24 ` [PATCH next v3 07/15] printk: introduce CONSOLE_LOG_MAX for improved multi-line support John Ogness
2021-03-02 13:54 ` Geert Uytterhoeven
2021-03-02 13:58 ` Geert Uytterhoeven
2021-03-02 14:34 ` John Ogness
2021-02-25 20:24 ` [PATCH next v3 08/15] printk: use seqcount_latch for clear_seq John Ogness
2021-02-25 20:24 ` [PATCH next v3 09/15] printk: use atomic64_t for devkmsg_user.seq John Ogness
2021-02-25 20:24 ` [PATCH next v3 10/15] printk: add syslog_lock John Ogness
2021-03-01 17:07 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 11/15] printk: kmsg_dumper: remove @active field John Ogness
2021-03-01 17:09 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 12/15] printk: introduce a kmsg_dump iterator John Ogness
2021-02-25 21:59 ` Kees Cook
2021-02-26 7:59 ` John Ogness
2021-03-01 18:07 ` Petr Mladek
2021-03-02 13:20 ` John Ogness
2021-03-02 13:55 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 13/15] printk: remove logbuf_lock John Ogness
2021-03-02 12:15 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 14/15] printk: kmsg_dump: remove _nolock() variants John Ogness
2021-02-25 20:24 ` [PATCH next v3 15/15] printk: console: remove unnecessary safe buffer usage John Ogness
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