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From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Jason Wessel <jason.wessel@windriver.com>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Douglas Anderson <dianders@chromium.org>,
	Sumit Garg <sumit.garg@linaro.org>,
	Cengiz Can <cengiz@kernel.wtf>,
	kgdb-bugreport@lists.sourceforge.net
Subject: [PATCH printk v1 09/10] kdb: if available, only use atomic consoles for output mirroring
Date: Tue,  3 Aug 2021 15:19:00 +0206	[thread overview]
Message-ID: <20210803131301.5588-10-john.ogness@linutronix.de> (raw)
In-Reply-To: <20210803131301.5588-1-john.ogness@linutronix.de>

Currently kdb uses the @oops_in_progress hack to mirror kdb output
to all active consoles from NMI context. Ignoring locks is unsafe.

Now that an NMI-safe atomic interface is available for consoles,
use only that interface to mirror kdb output if such a console is
available.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
 kernel/debug/kdb/kdb_io.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 6735ac36b718..871b89d6294b 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -544,6 +544,7 @@ static int kdb_search_string(char *searched, char *searchfor)
 
 static void kdb_msg_write(const char *msg, int msg_len)
 {
+	bool atomic_console_available;
 	struct console *c;
 	const char *cp;
 	int len;
@@ -559,11 +560,26 @@ static void kdb_msg_write(const char *msg, int msg_len)
 		cp++;
 	}
 
+	atomic_console_available = have_atomic_console();
+
 	for_each_console(c) {
 		if (!(c->flags & CON_ENABLED))
 			continue;
 		if (c == dbg_io_ops->cons)
 			continue;
+
+		/*
+		 * If any atomic consoles are available, only atomic
+		 * consoles are used.
+		 */
+		if (atomic_console_available) {
+			if (c->write_atomic) {
+				c->write_atomic(c, msg, msg_len);
+				touch_nmi_watchdog();
+			}
+			continue;
+		}
+
 		/*
 		 * Set oops_in_progress to encourage the console drivers to
 		 * disregard their internal spin locks: in the current calling
-- 
2.20.1


  parent reply	other threads:[~2021-08-03 13:13 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-03 13:12 [PATCH printk v1 00/10] printk: introduce atomic consoles and sync mode John Ogness
2021-08-03 13:12 ` [PATCH printk v1 01/10] printk: relocate printk cpulock functions John Ogness
2021-08-04  9:24   ` Petr Mladek
2021-08-03 13:12 ` [PATCH printk v1 02/10] printk: rename printk cpulock API and always disable interrupts John Ogness
2021-08-04  9:52   ` Petr Mladek
2021-08-03 13:12 ` [PATCH printk v1 03/10] kgdb: delay roundup if holding printk cpulock John Ogness
2021-08-03 14:25   ` Daniel Thompson
2021-08-03 15:30     ` John Ogness
2021-08-04 11:31       ` Daniel Thompson
2021-08-04 12:12         ` Petr Mladek
2021-08-04 15:04           ` Daniel Thompson
2021-08-05  3:46             ` John Ogness
2021-08-06 12:06               ` Daniel Thompson
2021-08-04 12:31       ` Petr Mladek
2021-08-03 13:12 ` [PATCH printk v1 04/10] printk: relocate printk_delay() John Ogness
2021-08-04 13:07   ` Petr Mladek
2021-08-03 13:12 ` [PATCH printk v1 05/10] printk: call boot_delay_msec() in printk_delay() John Ogness
2021-08-04 13:09   ` Petr Mladek
2021-08-31  1:04   ` Sergey Senozhatsky
2021-08-03 13:12 ` [PATCH printk v1 06/10] printk: use seqcount_latch for console_seq John Ogness
2021-08-05 12:16   ` Petr Mladek
2021-08-05 15:26     ` John Ogness
2021-08-06 15:56       ` Petr Mladek
2021-08-31  3:05         ` Sergey Senozhatsky
2021-08-03 13:12 ` [PATCH printk v1 07/10] console: add write_atomic interface John Ogness
2021-08-03 14:02   ` Andy Shevchenko
2021-08-06 10:56     ` John Ogness
2021-08-06 11:18       ` Andy Shevchenko
2021-08-31  2:55   ` Sergey Senozhatsky
2021-08-03 13:12 ` [PATCH printk v1 08/10] printk: introduce kernel sync mode John Ogness
2021-08-05 17:11   ` Petr Mladek
2021-08-05 21:25     ` John Ogness
2021-08-03 13:13 ` John Ogness [this message]
2021-08-03 13:13 ` [PATCH printk v1 10/10] serial: 8250: implement write_atomic John Ogness
2021-08-03 14:07   ` Andy Shevchenko
2021-08-05  7:47     ` Jiri Slaby
2021-08-05  8:26       ` John Ogness
2021-08-03 13:52 ` [PATCH printk v1 00/10] printk: introduce atomic consoles and sync mode Andy Shevchenko
2021-08-05 15:47 ` Petr Mladek
2021-08-31  0:33   ` Sergey Senozhatsky

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