linux-kernel - [PATCH -next] panic: complete the flush of the hard deadlock log messages to the serial port

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Message-ID: <20201123131359.34600-1-xuqiang36@huawei.com>
Date:   Mon, 23 Nov 2020 13:13:59 +0000
From:   Xu Qiang <xuqiang36@...wei.com>
To:     <akpm@...ux-foundation.org>, <keescook@...omium.org>,
        <mingo@...nel.org>, <peterz@...radead.org>, <mcgrof@...nel.org>,
        <huyue2@...ong.com>, <yangtiezhu@...ngson.cn>, <will@...nel.org>,
        <aquini@...hat.com>, <gpiccoli@...onical.com>,
        <xuqiang36@...wei.com>, <aik@...abs.ru>,
        <linux-kernel@...r.kernel.org>
CC:     <rui.xiang@...wei.com>
Subject: [PATCH -next] panic: complete the flush of the hard deadlock log messages to the serial port

when hardlockup_all_cpu_backtrace is on, and there are
a large number of cores in the system, it takes
a long time to output the hard deadlock logs of all cores
to the serial port. When the console_flush_on_panic function
in panic is executed, console_locked is still held.
As a result, garbled characters are displayed in the serial port log.

To solve this problem, wait for a maximum of 10s for the serial port
to be released before console_flush_on_panic.

Signed-off-by: Xu Qiang <xuqiang36@...wei.com>
---
 kernel/panic.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/panic.c b/kernel/panic.c
index 332736a72a58..0014788e8141 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -301,6 +301,14 @@ void panic(const char *fmt, ...)
 	 * panic() is not being callled from OOPS.
 	 */
 	debug_locks_off();
+
+	/* Wait for all CPUs to complete console_unlock */
+	for (i = 0; i < 10 * 1000; i++) {
+		if (console_trylock())
+			break;
+		mdelay(1);
+	}
+
 	console_flush_on_panic(CONSOLE_FLUSH_PENDING);
 
 	panic_print_sys_info();
-- 
2.25.0