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

* [PATCH -next] panic: complete the flush of the hard deadlock log messages to the serial port
@ 2020-11-23 13:13 Xu Qiang
  2020-11-23 19:52 ` Andrew Morton
  0 siblings, 1 reply; 4+ messages in thread
From: Xu Qiang @ 2020-11-23 13:13 UTC (permalink / raw)
  To: akpm, keescook, mingo, peterz, mcgrof, huyue2, yangtiezhu, will,
	aquini, gpiccoli, xuqiang36, aik, linux-kernel
  Cc: rui.xiang

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@huawei.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


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