[PATCH AUTOSEL 4.9 09/17] printk: Add panic_in_progress helper

[Sasha Levin]

From: Stephen Brennan <stephen.s.brennan@xxxxxxxxxx>

[ Upstream commit 77498617857f68496b360081dde1a492d40c28b2 ]

This will be used help avoid deadlocks during panics. Although it would
be better to include this in linux/panic.h, it would require that header
to include linux/atomic.h as well. On some architectures, this results
in a circular dependency as well. So instead add the helper directly to
printk.c.

Suggested-by: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Stephen Brennan <stephen.s.brennan@xxxxxxxxxx>
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
Link: https://lore.kernel.org/r/20220202171821.179394-2-stephen.s.brennan@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/printk/printk.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 9c17a2655551..f3e6fddb967a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -225,6 +225,11 @@ static int __down_trylock_console_sem(unsigned long ip)
 	up(&console_sem);\
 } while (0)
 
+static bool panic_in_progress(void)
+{
+	return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
+}
+
 /*
  * This is used for debugging the mess that is the VT code by
  * keeping track if we have the console semaphore held. It's
-- 
2.34.1