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
Subject: [PATCH printk-rework 09/12] um: synchronize kmsg_dumper
Date: Tue, 26 Jan 2021 22:21:48 +0106 [thread overview]
Message-ID: <20210126211551.26536-10-john.ogness@linutronix.de> (raw)
In-Reply-To: <20210126211551.26536-1-john.ogness@linutronix.de>
In preparation for removing printk's @logbuf_lock, dumpers that have
assumed to be protected against parallel calls must provide their own
synchronization. Add a locally static spinlock to synchronize the
kmsg_dump call and temporary buffer usage.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
arch/um/kernel/kmsg_dump.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index f38349ad00ea..173999422ed8 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 <shared/init.h>
#include <shared/kern.h>
@@ -9,8 +10,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
enum kmsg_dump_reason reason,
struct kmsg_dumper_iter *iter)
{
+ 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 */
@@ -25,11 +28,16 @@ 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(iter, true, line, sizeof(line), &len)) {
line[len] = '\0';
printf("%s", line);
}
+
+ spin_unlock_irqrestore(&lock, flags);
}
static struct kmsg_dumper kmsg_dumper = {
--
2.20.1
next prev parent reply other threads:[~2021-01-27 3:35 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 21:15 [PATCH printk-rework 00/12] printk: remove logbuf_lock John Ogness
2021-01-26 21:15 ` [PATCH printk-rework 01/12] printk: kmsg_dump: remove unused fields John Ogness
2021-01-26 21:15 ` [PATCH printk-rework 02/12] printk: refactor kmsg_dump_get_buffer() John Ogness
2021-01-26 21:15 ` [PATCH printk-rework 03/12] printk: consolidate kmsg_dump_get_buffer/syslog_print_all code John Ogness
[not found] ` <YBQgTQYTA5p6Wgj6@alley>
2021-02-01 9:49 ` John Ogness
2021-02-02 12:31 ` Petr Mladek
2021-01-26 21:15 ` [PATCH printk-rework 04/12] printk: define CONSOLE_LOG_MAX in printk.h John Ogness
[not found] ` <YBQtbKrdwUAZQB9v@alley>
2021-02-01 8:24 ` LINE_MAX: was: " John Ogness
2021-02-02 11:22 ` Petr Mladek
2021-01-26 21:15 ` [PATCH printk-rework 05/12] printk: use seqcount_latch for clear_seq John Ogness
2021-01-26 21:15 ` [PATCH printk-rework 06/12] printk: use atomic64_t for devkmsg_user.seq John Ogness
2021-01-26 21:15 ` [PATCH printk-rework 07/12] printk: add syslog_lock John Ogness
2021-02-01 12:26 ` Petr Mladek
2021-02-01 13:11 ` John Ogness
2021-02-02 12:50 ` Petr Mladek
2021-01-26 21:15 ` [PATCH printk-rework 08/12] printk: introduce a kmsg_dump iterator John Ogness
2021-02-01 13:17 ` Petr Mladek
2021-02-01 13:32 ` John Ogness
2021-01-26 21:15 ` John Ogness [this message]
2021-02-01 10:26 ` [PATCH printk-rework 09/12] um: synchronize kmsg_dumper Petr Mladek
2021-02-01 14:15 ` Petr Mladek
2021-02-01 16:51 ` John Ogness
2021-02-01 16:54 ` Richard Weinberger
2021-02-01 20:25 ` John Ogness
2021-02-01 20:40 ` Richard Weinberger
2021-02-02 13:26 ` Petr Mladek
2021-01-26 21:15 ` [PATCH printk-rework 10/12] hv: " John Ogness
2021-01-27 21:32 ` Michael Kelley
2021-02-01 10:56 ` John Ogness
2021-01-26 21:15 ` [PATCH printk-rework 11/12] printk: remove logbuf_lock John Ogness
2021-02-02 9:15 ` Petr Mladek
2021-02-02 11:41 ` John Ogness
2021-02-02 16:11 ` Petr Mladek
2021-01-26 21:15 ` [PATCH printk-rework 12/12] printk: kmsg_dump: remove _nolock() variants John Ogness
2021-02-02 9:45 ` Petr Mladek
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