[RFC][PATCH v4 -next 3/4]Skip subsequent kmsg_dump() function calls in panic path

[Seiji Aguchi <seiji.aguchi@hds.com>]

This patch skips subsequent kmsg_dump() function calls in panic path

With this patch, we can avoid deadlock due to the subsequent calls.
Actually, kmsg_dump(KMSG_DUMP_EMREG) is called after kmsg_dump(KMSG_DUMP_PANIC) 
when panic_timeout variable is set.

 Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>

---
 kernel/printk.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/kernel/printk.c b/kernel/printk.c
index 5294426..186d792 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1731,6 +1731,16 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 	const char *s1, *s2;
 	unsigned long l1, l2;
 	unsigned long flags;
+	static bool panicked;
+
+	/*
+	 * kmsg_dump() is skipped because we already got panic log.
+	 */
+	if (panicked)
+		return;
+
+	if (reason == KMSG_DUMP_PANIC)
+		panicked = true;
 
 	/*
 	 * Currently, "in_nmi() && reason != KMSG_DUMP_PANIC" case never happens
-- 
1.7.1